diff --git a/api/events/content.pb.go b/api/events/content.pb.go
index 2d127de10..44856d55c 100644
--- a/api/events/content.pb.go
+++ b/api/events/content.pb.go
@@ -8,7 +8,6 @@ import (
 	_ "github.com/containerd/containerd/protobuf/plugin"
 	_ "github.com/gogo/protobuf/gogoproto"
 	proto "github.com/gogo/protobuf/proto"
-	github_com_opencontainers_go_digest "github.com/opencontainers/go-digest"
 	io "io"
 	math "math"
 	math_bits "math/bits"
@@ -28,10 +27,10 @@ var _ = math.Inf
 const _ = proto.GoGoProtoPackageIsVersion3 // please upgrade the proto package
 
 type ContentDelete struct {
-	Digest               github_com_opencontainers_go_digest.Digest `protobuf:"bytes,1,opt,name=digest,proto3,customtype=github.com/opencontainers/go-digest.Digest" json:"digest"`
-	XXX_NoUnkeyedLiteral struct{}                                   `json:"-"`
-	XXX_unrecognized     []byte                                     `json:"-"`
-	XXX_sizecache        int32                                      `json:"-"`
+	Digest               string   `protobuf:"bytes,1,opt,name=digest,proto3" json:"digest,omitempty"`
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
 }
 
 func (m *ContentDelete) Reset()      { *m = ContentDelete{} }
@@ -75,21 +74,20 @@ func init() {
 }
 
 var fileDescriptor_dfb34b8b808e2ecd = []byte{
-	// 224 bytes of a gzipped FileDescriptorProto
+	// 194 bytes of a gzipped FileDescriptorProto
 	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0xe2, 0xb2, 0x4c, 0xcf, 0x2c, 0xc9,
 	0x28, 0x4d, 0xd2, 0x4b, 0xce, 0xcf, 0xd5, 0x4f, 0xce, 0xcf, 0x2b, 0x49, 0xcc, 0xcc, 0x4b, 0x2d,
 	0x4a, 0x41, 0x66, 0x26, 0x16, 0x64, 0xea, 0xa7, 0x96, 0xa5, 0xe6, 0x95, 0x14, 0x83, 0x45, 0x53,
 	0xf3, 0x4a, 0xf4, 0x0a, 0x8a, 0xf2, 0x4b, 0xf2, 0x85, 0x04, 0x11, 0x8a, 0xf4, 0x20, 0x0a, 0xa4,
 	0x44, 0xd2, 0xf3, 0xd3, 0xf3, 0xc1, 0xb2, 0xfa, 0x20, 0x16, 0x44, 0xa1, 0x94, 0x03, 0x41, 0x3b,
 	0xc0, 0xea, 0x92, 0x4a, 0xd3, 0xf4, 0x0b, 0x72, 0x4a, 0xd3, 0x33, 0xf3, 0xf4, 0xd3, 0x32, 0x53,
-	0x73, 0x52, 0x0a, 0x12, 0x4b, 0x32, 0x20, 0x26, 0x28, 0x45, 0x73, 0xf1, 0x3a, 0x43, 0xec, 0x76,
-	0x49, 0xcd, 0x49, 0x2d, 0x49, 0x15, 0xf2, 0xe2, 0x62, 0x4b, 0xc9, 0x4c, 0x4f, 0x2d, 0x2e, 0x91,
-	0x60, 0x54, 0x60, 0xd4, 0xe0, 0x74, 0x32, 0x3a, 0x71, 0x4f, 0x9e, 0xe1, 0xd6, 0x3d, 0x79, 0x2d,
-	0x24, 0xab, 0xf2, 0x0b, 0x52, 0xf3, 0xe0, 0x76, 0x14, 0xeb, 0xa7, 0xe7, 0xeb, 0x42, 0xb4, 0xe8,
-	0xb9, 0x80, 0xa9, 0x20, 0xa8, 0x09, 0x4e, 0x01, 0x27, 0x1e, 0xca, 0x31, 0xdc, 0x78, 0x28, 0xc7,
-	0xd0, 0xf0, 0x48, 0x8e, 0xf1, 0xc4, 0x23, 0x39, 0xc6, 0x0b, 0x8f, 0xe4, 0x18, 0x1f, 0x3c, 0x92,
-	0x63, 0x5c, 0xf0, 0x45, 0x8e, 0x31, 0xca, 0x88, 0x84, 0x00, 0xb2, 0x86, 0x50, 0x49, 0x6c, 0x60,
-	0x57, 0x1b, 0x03, 0x02, 0x00, 0x00, 0xff, 0xff, 0xee, 0x71, 0x10, 0x4c, 0x5d, 0x01, 0x00, 0x00,
+	0x73, 0x52, 0x0a, 0x12, 0x4b, 0x32, 0x20, 0x26, 0x28, 0xa9, 0x73, 0xf1, 0x3a, 0x43, 0xec, 0x76,
+	0x49, 0xcd, 0x49, 0x2d, 0x49, 0x15, 0x12, 0xe3, 0x62, 0x4b, 0xc9, 0x4c, 0x4f, 0x2d, 0x2e, 0x91,
+	0x60, 0x54, 0x60, 0xd4, 0xe0, 0x0c, 0x82, 0xf2, 0x9c, 0x02, 0x4e, 0x3c, 0x94, 0x63, 0xb8, 0xf1,
+	0x50, 0x8e, 0xa1, 0xe1, 0x91, 0x1c, 0xe3, 0x89, 0x47, 0x72, 0x8c, 0x17, 0x1e, 0xc9, 0x31, 0x3e,
+	0x78, 0x24, 0xc7, 0xb8, 0xe0, 0x8b, 0x1c, 0x63, 0x94, 0x11, 0x09, 0x9e, 0xb5, 0x86, 0x50, 0x49,
+	0x6c, 0x60, 0x17, 0x18, 0x03, 0x02, 0x00, 0x00, 0xff, 0xff, 0x43, 0xb0, 0xdf, 0x8c, 0x29, 0x01,
+	0x00, 0x00,
 }
 
 // Field returns the value for the given fieldpath as a string, if defined.
@@ -250,7 +248,7 @@ func (m *ContentDelete) Unmarshal(dAtA []byte) error {
 			if postIndex > l {
 				return io.ErrUnexpectedEOF
 			}
-			m.Digest = github_com_opencontainers_go_digest.Digest(dAtA[iNdEx:postIndex])
+			m.Digest = string(dAtA[iNdEx:postIndex])
 			iNdEx = postIndex
 		default:
 			iNdEx = preIndex
diff --git a/api/events/content.proto b/api/events/content.proto
index cfc22971d..c745d428d 100644
--- a/api/events/content.proto
+++ b/api/events/content.proto
@@ -25,5 +25,5 @@ option go_package = "github.com/containerd/containerd/api/events;events";
 option (containerd.plugin.fieldpath_all) = true;
 
 message ContentDelete {
-	string digest = 1 [(gogoproto.customtype) = "github.com/opencontainers/go-digest.Digest", (gogoproto.nullable) = false];
+	string digest = 1;
 }
diff --git a/api/next.pb.txt b/api/next.pb.txt
index 3d4b618a3..b420640ef 100644
--- a/api/next.pb.txt
+++ b/api/next.pb.txt
@@ -178,10 +178,6 @@ file {
       number: 1
       label: LABEL_OPTIONAL
       type: TYPE_STRING
-      options {
-        65003: "github.com/opencontainers/go-digest.Digest"
-        65001: 0
-      }
       json_name: "digest"
     }
   }
@@ -1178,10 +1174,6 @@ file {
       number: 1
       label: LABEL_OPTIONAL
       type: TYPE_STRING
-      options {
-        65003: "github.com/opencontainers/go-digest.Digest"
-        65001: 0
-      }
       json_name: "digest"
     }
     field {
@@ -1251,10 +1243,6 @@ file {
       number: 1
       label: LABEL_OPTIONAL
       type: TYPE_STRING
-      options {
-        65003: "github.com/opencontainers/go-digest.Digest"
-        65001: 0
-      }
       json_name: "digest"
     }
   }
@@ -1339,10 +1327,6 @@ file {
       number: 1
       label: LABEL_OPTIONAL
       type: TYPE_STRING
-      options {
-        65003: "github.com/opencontainers/go-digest.Digest"
-        65001: 0
-      }
       json_name: "digest"
     }
   }
@@ -1353,10 +1337,6 @@ file {
       number: 1
       label: LABEL_OPTIONAL
       type: TYPE_STRING
-      options {
-        65003: "github.com/opencontainers/go-digest.Digest"
-        65001: 0
-      }
       json_name: "digest"
     }
     field {
@@ -1443,10 +1423,6 @@ file {
       number: 6
       label: LABEL_OPTIONAL
       type: TYPE_STRING
-      options {
-        65003: "github.com/opencontainers/go-digest.Digest"
-        65001: 0
-      }
       json_name: "expected"
     }
   }
@@ -1524,10 +1500,6 @@ file {
       number: 4
       label: LABEL_OPTIONAL
       type: TYPE_STRING
-      options {
-        65003: "github.com/opencontainers/go-digest.Digest"
-        65001: 0
-      }
       json_name: "expected"
     }
     field {
@@ -1626,10 +1598,6 @@ file {
       number: 6
       label: LABEL_OPTIONAL
       type: TYPE_STRING
-      options {
-        65003: "github.com/opencontainers/go-digest.Digest"
-        65001: 0
-      }
       json_name: "digest"
     }
   }
@@ -1746,10 +1714,6 @@ file {
       number: 2
       label: LABEL_OPTIONAL
       type: TYPE_STRING
-      options {
-        65003: "github.com/opencontainers/go-digest.Digest"
-        65001: 0
-      }
       json_name: "digest"
     }
     field {
@@ -4157,10 +4121,6 @@ file {
       number: 2
       label: LABEL_OPTIONAL
       type: TYPE_STRING
-      options {
-        65003: "github.com/opencontainers/go-digest.Digest"
-        65001: 0
-      }
       json_name: "parentCheckpoint"
     }
     field {
diff --git a/api/services/content/v1/content.pb.go b/api/services/content/v1/content.pb.go
index 065027500..dcea7e426 100644
--- a/api/services/content/v1/content.pb.go
+++ b/api/services/content/v1/content.pb.go
@@ -11,7 +11,6 @@ import (
 	github_com_gogo_protobuf_sortkeys "github.com/gogo/protobuf/sortkeys"
 	github_com_gogo_protobuf_types "github.com/gogo/protobuf/types"
 	types "github.com/gogo/protobuf/types"
-	github_com_opencontainers_go_digest "github.com/opencontainers/go-digest"
 	grpc "google.golang.org/grpc"
 	codes "google.golang.org/grpc/codes"
 	status "google.golang.org/grpc/status"
@@ -81,7 +80,7 @@ func (WriteAction) EnumDescriptor() ([]byte, []int) {
 
 type Info struct {
 	// Digest is the hash identity of the blob.
-	Digest github_com_opencontainers_go_digest.Digest `protobuf:"bytes,1,opt,name=digest,proto3,customtype=github.com/opencontainers/go-digest.Digest" json:"digest"`
+	Digest string `protobuf:"bytes,1,opt,name=digest,proto3" json:"digest,omitempty"`
 	// Size is the total number of bytes in the blob.
 	Size_ int64 `protobuf:"varint,2,opt,name=size,proto3" json:"size,omitempty"`
 	// CreatedAt provides the time at which the blob was committed.
@@ -130,10 +129,10 @@ func (m *Info) XXX_DiscardUnknown() {
 var xxx_messageInfo_Info proto.InternalMessageInfo
 
 type InfoRequest struct {
-	Digest               github_com_opencontainers_go_digest.Digest `protobuf:"bytes,1,opt,name=digest,proto3,customtype=github.com/opencontainers/go-digest.Digest" json:"digest"`
-	XXX_NoUnkeyedLiteral struct{}                                   `json:"-"`
-	XXX_unrecognized     []byte                                     `json:"-"`
-	XXX_sizecache        int32                                      `json:"-"`
+	Digest               string   `protobuf:"bytes,1,opt,name=digest,proto3" json:"digest,omitempty"`
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
 }
 
 func (m *InfoRequest) Reset()      { *m = InfoRequest{} }
@@ -382,10 +381,10 @@ var xxx_messageInfo_ListContentResponse proto.InternalMessageInfo
 
 type DeleteContentRequest struct {
 	// Digest specifies which content to delete.
-	Digest               github_com_opencontainers_go_digest.Digest `protobuf:"bytes,1,opt,name=digest,proto3,customtype=github.com/opencontainers/go-digest.Digest" json:"digest"`
-	XXX_NoUnkeyedLiteral struct{}                                   `json:"-"`
-	XXX_unrecognized     []byte                                     `json:"-"`
-	XXX_sizecache        int32                                      `json:"-"`
+	Digest               string   `protobuf:"bytes,1,opt,name=digest,proto3" json:"digest,omitempty"`
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
 }
 
 func (m *DeleteContentRequest) Reset()      { *m = DeleteContentRequest{} }
@@ -424,7 +423,7 @@ var xxx_messageInfo_DeleteContentRequest proto.InternalMessageInfo
 // data from a stored object.
 type ReadContentRequest struct {
 	// Digest is the hash identity to read.
-	Digest github_com_opencontainers_go_digest.Digest `protobuf:"bytes,1,opt,name=digest,proto3,customtype=github.com/opencontainers/go-digest.Digest" json:"digest"`
+	Digest string `protobuf:"bytes,1,opt,name=digest,proto3" json:"digest,omitempty"`
 	// Offset specifies the number of bytes from the start at which to begin
 	// the read. If zero or less, the read will be from the start. This uses
 	// standard zero-indexed semantics.
@@ -511,15 +510,15 @@ func (m *ReadContentResponse) XXX_DiscardUnknown() {
 var xxx_messageInfo_ReadContentResponse proto.InternalMessageInfo
 
 type Status struct {
-	StartedAt            time.Time                                  `protobuf:"bytes,1,opt,name=started_at,json=startedAt,proto3,stdtime" json:"started_at"`
-	UpdatedAt            time.Time                                  `protobuf:"bytes,2,opt,name=updated_at,json=updatedAt,proto3,stdtime" json:"updated_at"`
-	Ref                  string                                     `protobuf:"bytes,3,opt,name=ref,proto3" json:"ref,omitempty"`
-	Offset               int64                                      `protobuf:"varint,4,opt,name=offset,proto3" json:"offset,omitempty"`
-	Total                int64                                      `protobuf:"varint,5,opt,name=total,proto3" json:"total,omitempty"`
-	Expected             github_com_opencontainers_go_digest.Digest `protobuf:"bytes,6,opt,name=expected,proto3,customtype=github.com/opencontainers/go-digest.Digest" json:"expected"`
-	XXX_NoUnkeyedLiteral struct{}                                   `json:"-"`
-	XXX_unrecognized     []byte                                     `json:"-"`
-	XXX_sizecache        int32                                      `json:"-"`
+	StartedAt            time.Time `protobuf:"bytes,1,opt,name=started_at,json=startedAt,proto3,stdtime" json:"started_at"`
+	UpdatedAt            time.Time `protobuf:"bytes,2,opt,name=updated_at,json=updatedAt,proto3,stdtime" json:"updated_at"`
+	Ref                  string    `protobuf:"bytes,3,opt,name=ref,proto3" json:"ref,omitempty"`
+	Offset               int64     `protobuf:"varint,4,opt,name=offset,proto3" json:"offset,omitempty"`
+	Total                int64     `protobuf:"varint,5,opt,name=total,proto3" json:"total,omitempty"`
+	Expected             string    `protobuf:"bytes,6,opt,name=expected,proto3" json:"expected,omitempty"`
+	XXX_NoUnkeyedLiteral struct{}  `json:"-"`
+	XXX_unrecognized     []byte    `json:"-"`
+	XXX_sizecache        int32     `json:"-"`
 }
 
 func (m *Status) Reset()      { *m = Status{} }
@@ -745,7 +744,7 @@ type WriteContentRequest struct {
 	// Only the latest version will be used to check the content against the
 	// digest. It is only required to include it on a single message, before or
 	// with the commit action message.
-	Expected github_com_opencontainers_go_digest.Digest `protobuf:"bytes,4,opt,name=expected,proto3,customtype=github.com/opencontainers/go-digest.Digest" json:"expected"`
+	Expected string `protobuf:"bytes,4,opt,name=expected,proto3" json:"expected,omitempty"`
 	// Offset specifies the number of bytes from the start at which to begin
 	// the write. For most implementations, this means from the start of the
 	// file. This uses standard, zero-indexed semantics.
@@ -829,10 +828,10 @@ type WriteContentResponse struct {
 	// Digest, if present, includes the digest up to the currently committed
 	// bytes. If action is commit, this field will be set. It is implementation
 	// defined if this is set for other actions.
-	Digest               github_com_opencontainers_go_digest.Digest `protobuf:"bytes,6,opt,name=digest,proto3,customtype=github.com/opencontainers/go-digest.Digest" json:"digest"`
-	XXX_NoUnkeyedLiteral struct{}                                   `json:"-"`
-	XXX_unrecognized     []byte                                     `json:"-"`
-	XXX_sizecache        int32                                      `json:"-"`
+	Digest               string   `protobuf:"bytes,6,opt,name=digest,proto3" json:"digest,omitempty"`
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
 }
 
 func (m *WriteContentResponse) Reset()      { *m = WriteContentResponse{} }
@@ -935,75 +934,73 @@ func init() {
 }
 
 var fileDescriptor_468430ba3e400391 = []byte{
-	// 1079 bytes of a gzipped FileDescriptorProto
-	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0xb4, 0x57, 0xcd, 0x6f, 0x1b, 0x45,
-	0x14, 0xcf, 0x78, 0xed, 0x4d, 0xf2, 0x9c, 0x16, 0x33, 0x31, 0x95, 0xb5, 0x08, 0x7b, 0xbb, 0x42,
-	0xc8, 0x6a, 0xc9, 0x3a, 0x75, 0x7a, 0x00, 0x2a, 0x01, 0x8e, 0x9b, 0xaa, 0x41, 0x4d, 0x41, 0x5b,
-	0x97, 0x88, 0x5e, 0xca, 0xda, 0x1e, 0x9b, 0x55, 0x6c, 0xaf, 0xbb, 0x33, 0xb6, 0x08, 0x27, 0x2e,
-	0x48, 0x28, 0xea, 0x01, 0x71, 0xcf, 0x05, 0xf8, 0x2b, 0x38, 0x70, 0xce, 0x91, 0x23, 0xe2, 0xd0,
-	0xd2, 0xfc, 0x0f, 0xdc, 0xd1, 0xcc, 0xce, 0xda, 0xeb, 0x8f, 0xb0, 0xb6, 0xe3, 0x9e, 0xfc, 0x66,
-	0xf6, 0xfd, 0xde, 0xf7, 0xc7, 0x18, 0xee, 0x35, 0x1d, 0xf6, 0x4d, 0xaf, 0x6a, 0xd6, 0xdc, 0x76,
-	0xa1, 0xe6, 0x76, 0x98, 0xed, 0x74, 0x88, 0x57, 0x0f, 0x93, 0x76, 0xd7, 0x29, 0x50, 0xe2, 0xf5,
-	0x9d, 0x1a, 0xa1, 0xe2, 0x9e, 0x74, 0x58, 0xa1, 0x7f, 0x2b, 0x20, 0xcd, 0xae, 0xe7, 0x32, 0x17,
-	0x67, 0x87, 0x08, 0x33, 0xe0, 0x36, 0x03, 0x96, 0xfe, 0x2d, 0x2d, 0xdd, 0x74, 0x9b, 0xae, 0x60,
-	0x2d, 0x70, 0xca, 0x47, 0x69, 0x7a, 0xd3, 0x75, 0x9b, 0x2d, 0x52, 0x10, 0xa7, 0x6a, 0xaf, 0x51,
-	0x68, 0x38, 0xa4, 0x55, 0x7f, 0xda, 0xb6, 0xe9, 0x91, 0xe4, 0xc8, 0x8d, 0x73, 0x30, 0xa7, 0x4d,
-	0x28, 0xb3, 0xdb, 0x5d, 0xc9, 0xf0, 0xf6, 0x38, 0x03, 0x69, 0x77, 0xd9, 0xb1, 0xff, 0xd1, 0xf8,
-	0x37, 0x06, 0xf1, 0xfd, 0x4e, 0xc3, 0xc5, 0x9f, 0x81, 0x5a, 0x77, 0x9a, 0x84, 0xb2, 0x0c, 0xd2,
-	0x51, 0x7e, 0x7d, 0xb7, 0x78, 0xf6, 0x22, 0xb7, 0xf2, 0xf7, 0x8b, 0xdc, 0x8d, 0x90, 0xfb, 0x6e,
-	0x97, 0x74, 0x06, 0x5e, 0xd0, 0x42, 0xd3, 0xdd, 0xf2, 0x21, 0xe6, 0x5d, 0xf1, 0x63, 0x49, 0x09,
-	0x18, 0x43, 0x9c, 0x3a, 0xdf, 0x91, 0x4c, 0x4c, 0x47, 0x79, 0xc5, 0x12, 0x34, 0x2e, 0x03, 0xd4,
-	0x3c, 0x62, 0x33, 0x52, 0x7f, 0x6a, 0xb3, 0x8c, 0xa2, 0xa3, 0x7c, 0xb2, 0xa8, 0x99, 0xbe, 0x69,
-	0x66, 0x60, 0x9a, 0x59, 0x09, 0x6c, 0xdf, 0x5d, 0xe3, 0xfa, 0x7f, 0x7a, 0x99, 0x43, 0xd6, 0xba,
-	0xc4, 0x95, 0x18, 0x17, 0xd2, 0xeb, 0xd6, 0x03, 0x21, 0xf1, 0x79, 0x84, 0x48, 0x5c, 0x89, 0xe1,
-	0xfb, 0xa0, 0xb6, 0xec, 0x2a, 0x69, 0xd1, 0x4c, 0x42, 0x57, 0xf2, 0xc9, 0xe2, 0xb6, 0xf9, 0xff,
-	0x99, 0x31, 0x79, 0x7c, 0xcc, 0x07, 0x02, 0xb2, 0xd7, 0x61, 0xde, 0xb1, 0x25, 0xf1, 0xda, 0x87,
-	0x90, 0x0c, 0x5d, 0xe3, 0x14, 0x28, 0x47, 0xe4, 0xd8, 0x8f, 0x9f, 0xc5, 0x49, 0x9c, 0x86, 0x44,
-	0xdf, 0x6e, 0xf5, 0xfc, 0x48, 0xac, 0x5b, 0xfe, 0xe1, 0xa3, 0xd8, 0x07, 0xc8, 0xf8, 0x0a, 0x92,
-	0x5c, 0xac, 0x45, 0x9e, 0xf5, 0x78, 0xc4, 0x96, 0x18, 0x7d, 0xe3, 0x21, 0x6c, 0xf8, 0xa2, 0x69,
-	0xd7, 0xed, 0x50, 0x82, 0x3f, 0x86, 0xb8, 0xd3, 0x69, 0xb8, 0x42, 0x72, 0xb2, 0xf8, 0xee, 0x2c,
-	0xde, 0xee, 0xc6, 0xb9, 0x7e, 0x4b, 0xe0, 0x8c, 0xe7, 0x08, 0xae, 0x3c, 0x16, 0xd1, 0x0b, 0xac,
-	0xbd, 0xa4, 0x44, 0x7c, 0x07, 0x92, 0x7e, 0x3a, 0x44, 0x1d, 0x8b, 0xe0, 0x4c, 0xcb, 0xe3, 0x3d,
-	0x5e, 0xea, 0x07, 0x36, 0x3d, 0xb2, 0x64, 0xd6, 0x39, 0x6d, 0x7c, 0x01, 0x57, 0x03, 0x6b, 0x96,
-	0xe4, 0xa0, 0x09, 0xf8, 0x81, 0x43, 0x59, 0xd9, 0x67, 0x09, 0x9c, 0xcc, 0xc0, 0x6a, 0xc3, 0x69,
-	0x31, 0xe2, 0xd1, 0x0c, 0xd2, 0x95, 0xfc, 0xba, 0x15, 0x1c, 0x8d, 0xc7, 0xb0, 0x39, 0xc2, 0x3f,
-	0x61, 0x86, 0xb2, 0x90, 0x19, 0x55, 0x48, 0xdf, 0x25, 0x2d, 0xc2, 0xc8, 0x98, 0x21, 0xcb, 0xac,
-	0x8d, 0xe7, 0x08, 0xb0, 0x45, 0xec, 0xfa, 0xeb, 0x53, 0x81, 0xaf, 0x81, 0xea, 0x36, 0x1a, 0x94,
-	0x30, 0xd9, 0xfe, 0xf2, 0x34, 0x18, 0x0a, 0xca, 0x70, 0x28, 0x18, 0x25, 0xd8, 0x1c, 0xb1, 0x46,
-	0x46, 0x72, 0x28, 0x02, 0x8d, 0x8b, 0xa8, 0xdb, 0xcc, 0x16, 0x82, 0x37, 0x2c, 0x41, 0x1b, 0xbf,
-	0xc4, 0x40, 0x7d, 0xc4, 0x6c, 0xd6, 0xa3, 0x7c, 0x3a, 0x50, 0x66, 0x7b, 0x72, 0x3a, 0xa0, 0x79,
-	0xa6, 0x83, 0xc4, 0x4d, 0x8c, 0x98, 0xd8, 0x62, 0x23, 0x26, 0x05, 0x8a, 0x47, 0x1a, 0xc2, 0xd5,
-	0x75, 0x8b, 0x93, 0x21, 0x97, 0xe2, 0x23, 0x2e, 0xa5, 0x21, 0xc1, 0x5c, 0x66, 0xb7, 0x32, 0x09,
-	0x71, 0xed, 0x1f, 0xf0, 0x43, 0x58, 0x23, 0xdf, 0x76, 0x49, 0x8d, 0x91, 0x7a, 0x46, 0x5d, 0x38,
-	0x23, 0x03, 0x19, 0xc6, 0x75, 0xb8, 0xe2, 0xc7, 0x28, 0x48, 0xb8, 0x34, 0x10, 0x0d, 0x0c, 0xe4,
-	0x6d, 0x15, 0xb0, 0x0c, 0xea, 0x59, 0xa5, 0xe2, 0x46, 0x86, 0xf2, 0xbd, 0xa8, 0x8a, 0x96, 0x78,
-	0x89, 0x32, 0x0a, 0x7e, 0x9b, 0xf8, 0xb7, 0x84, 0x46, 0xf7, 0xd5, 0xd7, 0x90, 0x1e, 0x05, 0x48,
-	0x43, 0xee, 0xc3, 0x1a, 0x95, 0x77, 0xb2, 0xb9, 0x66, 0x34, 0x45, 0xb6, 0xd7, 0x00, 0x6d, 0xfc,
-	0xac, 0xc0, 0xe6, 0xa1, 0xe7, 0x4c, 0xb4, 0x58, 0x19, 0x54, 0xbb, 0xc6, 0x1c, 0xb7, 0x23, 0x5c,
-	0xbd, 0x5a, 0xbc, 0x19, 0x25, 0x5f, 0x08, 0x29, 0x09, 0x88, 0x25, 0xa1, 0x41, 0x4c, 0x63, 0xc3,
-	0xa4, 0x0f, 0x92, 0xab, 0x5c, 0x94, 0xdc, 0xf8, 0xe5, 0x93, 0x1b, 0x2a, 0xad, 0xc4, 0xd4, 0x6e,
-	0x51, 0x87, 0xdd, 0x82, 0x0f, 0x07, 0xbb, 0x6f, 0x55, 0x04, 0xf2, 0x93, 0x99, 0x1c, 0x1d, 0x8d,
-	0xd6, 0xb2, 0x57, 0xe1, 0xcb, 0x18, 0xa4, 0x47, 0xd5, 0xc8, 0xbc, 0x2f, 0x25, 0x2b, 0xa3, 0x43,
-	0x21, 0xb6, 0x8c, 0xa1, 0xa0, 0x2c, 0x36, 0x14, 0xe6, 0x1b, 0x01, 0xc3, 0x91, 0xac, 0x5e, 0x7a,
-	0xea, 0xeb, 0xb0, 0x51, 0xaa, 0xba, 0x1e, 0xbb, 0xb0, 0xfb, 0x6f, 0xfc, 0x80, 0x20, 0x19, 0x8a,
-	0x1e, 0x7e, 0x07, 0xe2, 0x8f, 0x2a, 0xa5, 0x4a, 0x6a, 0x45, 0xdb, 0x3c, 0x39, 0xd5, 0xdf, 0x08,
-	0x7d, 0xe2, 0x9d, 0x85, 0x73, 0x90, 0x38, 0xb4, 0xf6, 0x2b, 0x7b, 0x29, 0xa4, 0xa5, 0x4f, 0x4e,
-	0xf5, 0x54, 0xe8, 0xbb, 0x20, 0xf1, 0x75, 0x50, 0xcb, 0x9f, 0x1f, 0x1c, 0xec, 0x57, 0x52, 0x31,
-	0xed, 0xad, 0x93, 0x53, 0xfd, 0xcd, 0x10, 0x47, 0xd9, 0x6d, 0xb7, 0x1d, 0xa6, 0x6d, 0xfe, 0xf8,
-	0x6b, 0x76, 0xe5, 0xf7, 0xdf, 0xb2, 0x61, 0xbd, 0xc5, 0x3f, 0x56, 0x61, 0x55, 0x96, 0x01, 0xb6,
-	0xe5, 0xcb, 0xf4, 0xe6, 0x2c, 0x9b, 0x54, 0xba, 0xa6, 0xbd, 0x3f, 0x1b, 0xb3, 0xac, 0xb0, 0x26,
-	0xa8, 0xfe, 0x5b, 0x02, 0x6f, 0x45, 0xe1, 0x46, 0x5e, 0x40, 0x9a, 0x39, 0x2b, 0xbb, 0x54, 0xf4,
-	0x0c, 0xe2, 0x7c, 0xb4, 0xe1, 0x62, 0x14, 0x6e, 0xf2, 0x21, 0xa2, 0xed, 0xcc, 0x85, 0xf1, 0x15,
-	0x6e, 0x23, 0xfc, 0x25, 0xa8, 0xfe, 0x73, 0x02, 0xdf, 0x8e, 0x12, 0x30, 0xed, 0xd9, 0xa1, 0x5d,
-	0x9b, 0xa8, 0xef, 0x3d, 0xfe, 0xbf, 0x81, 0xbb, 0xc2, 0x77, 0x76, 0xb4, 0x2b, 0x93, 0xef, 0x8c,
-	0x68, 0x57, 0xa6, 0xbc, 0x06, 0xb6, 0x11, 0x4f, 0x93, 0x5c, 0xf1, 0x5b, 0x33, 0xee, 0xa0, 0x59,
-	0xd3, 0x34, 0xb6, 0xf2, 0x8e, 0x61, 0x23, 0xbc, 0x81, 0xf0, 0x4c, 0xa1, 0x1f, 0x5b, 0x70, 0xda,
-	0xed, 0xf9, 0x40, 0x52, 0x75, 0x1f, 0x12, 0x7e, 0xeb, 0xec, 0x2c, 0x30, 0x92, 0xa3, 0x75, 0x4e,
-	0x1b, 0xb0, 0x79, 0xb4, 0x8d, 0xf0, 0x01, 0x24, 0xc4, 0x6c, 0xc0, 0x91, 0x9d, 0x13, 0x1e, 0x21,
-	0x17, 0x55, 0xc7, 0xee, 0x93, 0xb3, 0x57, 0xd9, 0x95, 0xbf, 0x5e, 0x65, 0x57, 0xbe, 0x3f, 0xcf,
-	0xa2, 0xb3, 0xf3, 0x2c, 0xfa, 0xf3, 0x3c, 0x8b, 0xfe, 0x39, 0xcf, 0xa2, 0x27, 0x9f, 0x2e, 0xfa,
-	0x3f, 0xfa, 0x8e, 0x24, 0xab, 0xaa, 0xd0, 0xb5, 0xf3, 0x5f, 0x00, 0x00, 0x00, 0xff, 0xff, 0xbf,
-	0xc1, 0xae, 0xf1, 0x92, 0x0f, 0x00, 0x00,
+	// 1042 bytes of a gzipped FileDescriptorProto
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0xac, 0x57, 0x4f, 0x8f, 0xdb, 0x44,
+	0x14, 0xdf, 0x89, 0x13, 0xef, 0xe6, 0x65, 0x5b, 0xc2, 0x24, 0x54, 0x91, 0x11, 0x5e, 0xd7, 0x02,
+	0x14, 0x51, 0xea, 0x6c, 0xb3, 0x3d, 0x00, 0x95, 0x80, 0x6c, 0xd8, 0xaa, 0x2b, 0x75, 0x01, 0xb9,
+	0x29, 0x8b, 0x7a, 0x29, 0x4e, 0x32, 0x09, 0xd6, 0x26, 0x71, 0x6a, 0x4f, 0x22, 0x96, 0x13, 0x17,
+	0x24, 0xb4, 0xe2, 0xc0, 0x17, 0xd8, 0x13, 0xdc, 0xf8, 0x06, 0x1c, 0x90, 0xb8, 0xed, 0x91, 0x23,
+	0xa7, 0x42, 0xf7, 0x03, 0xf0, 0x19, 0xd0, 0x8c, 0xc7, 0x89, 0x9d, 0x3f, 0xd8, 0x49, 0xf7, 0xf6,
+	0x66, 0xfc, 0x7e, 0xef, 0xef, 0xef, 0xcd, 0x4b, 0xe0, 0x7e, 0xd7, 0xa6, 0x5f, 0x8f, 0x9a, 0x46,
+	0xcb, 0xe9, 0x57, 0x5a, 0xce, 0x80, 0x5a, 0xf6, 0x80, 0xb8, 0xed, 0xb0, 0x68, 0x0d, 0xed, 0x8a,
+	0x47, 0xdc, 0xb1, 0xdd, 0x22, 0x1e, 0xbf, 0x27, 0x03, 0x5a, 0x19, 0xdf, 0x09, 0x44, 0x63, 0xe8,
+	0x3a, 0xd4, 0xc1, 0xea, 0x14, 0x61, 0x04, 0xda, 0x46, 0xa0, 0x32, 0xbe, 0xa3, 0x14, 0xbb, 0x4e,
+	0xd7, 0xe1, 0xaa, 0x15, 0x26, 0xf9, 0x28, 0x45, 0xeb, 0x3a, 0x4e, 0xb7, 0x47, 0x2a, 0xfc, 0xd4,
+	0x1c, 0x75, 0x2a, 0x1d, 0x9b, 0xf4, 0xda, 0x4f, 0xfb, 0x96, 0x77, 0x22, 0x34, 0x76, 0x66, 0x35,
+	0xa8, 0xdd, 0x27, 0x1e, 0xb5, 0xfa, 0x43, 0xa1, 0xf0, 0xfa, 0xac, 0x02, 0xe9, 0x0f, 0xe9, 0xa9,
+	0xff, 0x51, 0xff, 0x23, 0x05, 0xe9, 0xc3, 0x41, 0xc7, 0xc1, 0x37, 0x40, 0x6e, 0xdb, 0x5d, 0xe2,
+	0xd1, 0x12, 0xd2, 0x50, 0x39, 0x6b, 0x8a, 0x13, 0xc6, 0x90, 0xf6, 0xec, 0x6f, 0x49, 0x29, 0xa5,
+	0xa1, 0xb2, 0x64, 0x72, 0x19, 0xd7, 0x01, 0x5a, 0x2e, 0xb1, 0x28, 0x69, 0x3f, 0xb5, 0x68, 0x49,
+	0xd2, 0x50, 0x39, 0x57, 0x55, 0x0c, 0xdf, 0x8d, 0x11, 0xb8, 0x31, 0x1a, 0x41, 0x1c, 0xfb, 0x5b,
+	0x17, 0xcf, 0x77, 0x36, 0x7e, 0xfa, 0x7b, 0x07, 0x99, 0x59, 0x81, 0xab, 0x51, 0x66, 0x64, 0x34,
+	0x6c, 0x07, 0x46, 0xd2, 0xab, 0x18, 0x11, 0xb8, 0x1a, 0xc5, 0x0f, 0x40, 0xee, 0x59, 0x4d, 0xd2,
+	0xf3, 0x4a, 0x19, 0x4d, 0x2a, 0xe7, 0xaa, 0xbb, 0xc6, 0xff, 0x57, 0xd9, 0x60, 0xb9, 0x1a, 0x0f,
+	0x39, 0xe4, 0x60, 0x40, 0xdd, 0x53, 0x53, 0xe0, 0x95, 0xf7, 0x21, 0x17, 0xba, 0xc6, 0x79, 0x90,
+	0x4e, 0xc8, 0xa9, 0xa8, 0x05, 0x13, 0x71, 0x11, 0x32, 0x63, 0xab, 0x37, 0xf2, 0x2b, 0x91, 0x35,
+	0xfd, 0xc3, 0x07, 0xa9, 0xf7, 0x90, 0xfe, 0x16, 0xe4, 0x98, 0x59, 0x93, 0x3c, 0x1b, 0xb1, 0x8a,
+	0x2d, 0xa9, 0xa4, 0xfe, 0x29, 0x6c, 0xfb, 0x6a, 0xde, 0xd0, 0x19, 0x78, 0x04, 0x7f, 0x08, 0x69,
+	0x7b, 0xd0, 0x71, 0xb8, 0x56, 0xae, 0xfa, 0x66, 0x92, 0xc8, 0xf7, 0xd3, 0xac, 0x08, 0x26, 0xc7,
+	0xe9, 0x3f, 0x22, 0xb8, 0xf6, 0x98, 0x57, 0x22, 0xf0, 0xfc, 0x92, 0x16, 0xf1, 0x3d, 0xc8, 0xf9,
+	0xa5, 0xe5, 0xfc, 0xe2, 0x89, 0x2e, 0xea, 0xc9, 0x7d, 0x46, 0xc1, 0x23, 0xcb, 0x3b, 0x31, 0x45,
+	0x07, 0x99, 0xac, 0x7f, 0x0e, 0xd7, 0x83, 0x68, 0xae, 0x28, 0x41, 0x03, 0xf0, 0x43, 0xdb, 0xa3,
+	0x75, 0x5f, 0x25, 0x48, 0xb2, 0x04, 0x9b, 0x1d, 0xbb, 0x47, 0x89, 0xeb, 0x95, 0x90, 0x26, 0x95,
+	0xb3, 0x66, 0x70, 0xd4, 0x1f, 0x43, 0x21, 0xa2, 0x3f, 0x17, 0x86, 0xb4, 0x66, 0x18, 0xc5, 0x4f,
+	0x48, 0x8f, 0x50, 0x32, 0x13, 0xc8, 0xb2, 0x3e, 0x7f, 0x09, 0xd8, 0x24, 0x56, 0x3b, 0x99, 0x36,
+	0xbb, 0x77, 0x3a, 0x1d, 0x8f, 0x50, 0x31, 0x61, 0xe2, 0x34, 0x99, 0x3b, 0x69, 0x3a, 0x77, 0x7a,
+	0x0d, 0x0a, 0x11, 0xcb, 0x22, 0xc1, 0xa9, 0x09, 0x34, 0x6b, 0xa2, 0x6d, 0x51, 0x8b, 0x1b, 0xde,
+	0x36, 0xb9, 0xac, 0xff, 0x8b, 0x40, 0x7e, 0x44, 0x2d, 0x3a, 0xf2, 0xd8, 0x00, 0x7a, 0xd4, 0x72,
+	0xc5, 0x00, 0xa2, 0x55, 0x06, 0x50, 0xe0, 0xe6, 0xa6, 0x38, 0xb5, 0xde, 0x14, 0xe7, 0x41, 0x72,
+	0x49, 0x87, 0xa7, 0x9a, 0x35, 0x99, 0x18, 0x4a, 0x29, 0x1d, 0x49, 0xa9, 0x08, 0x19, 0xea, 0x50,
+	0xab, 0x57, 0xca, 0xf0, 0x6b, 0xff, 0x80, 0x15, 0xd8, 0x22, 0xdf, 0x0c, 0x49, 0x8b, 0x92, 0x76,
+	0x49, 0xe6, 0x46, 0x26, 0x67, 0xfd, 0x26, 0x5c, 0xf3, 0xf3, 0x0d, 0x1a, 0x21, 0x9c, 0xa1, 0x89,
+	0x33, 0xc6, 0xdc, 0x40, 0x65, 0x42, 0x19, 0xd9, 0xe3, 0x37, 0xa2, 0x2c, 0x6f, 0xc7, 0x91, 0x46,
+	0xe0, 0x05, 0x4a, 0xaf, 0xf8, 0x4c, 0xf4, 0x6f, 0x89, 0x17, 0x4f, 0xdd, 0xaf, 0xa0, 0x18, 0x05,
+	0x88, 0x40, 0x1e, 0xc0, 0x96, 0x27, 0xee, 0x04, 0x7f, 0x13, 0x86, 0x22, 0x18, 0x3c, 0x41, 0xeb,
+	0xcf, 0x53, 0x50, 0x38, 0x76, 0xed, 0x39, 0x16, 0xd7, 0x41, 0xb6, 0x5a, 0xd4, 0x76, 0x06, 0x3c,
+	0xd5, 0xeb, 0xd5, 0x5b, 0x71, 0xf6, 0xb9, 0x91, 0x1a, 0x87, 0x98, 0x02, 0x1a, 0xd4, 0x34, 0x35,
+	0x6d, 0xe0, 0xa4, 0x51, 0xd2, 0xb2, 0x46, 0xa5, 0xa3, 0x8d, 0x0a, 0xb5, 0x3c, 0xb3, 0x90, 0xc5,
+	0xf2, 0x94, 0xc5, 0xf8, 0x78, 0xf2, 0xec, 0x6f, 0xf2, 0xa2, 0x7c, 0x94, 0x28, 0xe8, 0x68, 0xe6,
+	0x57, 0xbd, 0x05, 0x7e, 0x4d, 0x41, 0x31, 0xea, 0x46, 0xf4, 0xf0, 0x4a, 0x2a, 0x1c, 0x1d, 0xd6,
+	0xd4, 0x55, 0x0c, 0xab, 0xb4, 0xde, 0xb0, 0xae, 0x36, 0x9a, 0xd3, 0x67, 0x4f, 0x8e, 0x3c, 0x92,
+	0x1a, 0x6c, 0xd7, 0x9a, 0x8e, 0x4b, 0x97, 0x4e, 0xe5, 0x3b, 0xdf, 0x23, 0xc8, 0x85, 0x2a, 0x81,
+	0xdf, 0x80, 0xf4, 0xa3, 0x46, 0xad, 0x91, 0xdf, 0x50, 0x0a, 0x67, 0xe7, 0xda, 0x2b, 0xa1, 0x4f,
+	0x8c, 0xf1, 0x78, 0x07, 0x32, 0xc7, 0xe6, 0x61, 0xe3, 0x20, 0x8f, 0x94, 0xe2, 0xd9, 0xb9, 0x96,
+	0x0f, 0x7d, 0xe7, 0x22, 0xbe, 0x09, 0x72, 0xfd, 0xb3, 0xa3, 0xa3, 0xc3, 0x46, 0x3e, 0xa5, 0xbc,
+	0x76, 0x76, 0xae, 0xbd, 0x1a, 0xd2, 0xa8, 0x3b, 0xfd, 0xbe, 0x4d, 0x95, 0xc2, 0x0f, 0x3f, 0xab,
+	0x1b, 0xbf, 0xfd, 0xa2, 0x86, 0xfd, 0x56, 0x7f, 0xdf, 0x84, 0x4d, 0xd1, 0x52, 0x6c, 0x89, 0x1f,
+	0x4b, 0xb7, 0x92, 0x2c, 0x11, 0x91, 0x9a, 0xf2, 0x6e, 0x32, 0x65, 0xc1, 0x96, 0x2e, 0xc8, 0xfe,
+	0x1a, 0xc5, 0xb7, 0xe3, 0x70, 0x91, 0xe5, 0xaf, 0x18, 0x49, 0xd5, 0x85, 0xa3, 0x67, 0x90, 0x66,
+	0x4f, 0x0e, 0xae, 0xc6, 0xe1, 0xe6, 0x77, 0xb0, 0xb2, 0xb7, 0x12, 0xc6, 0x77, 0xb8, 0x8b, 0xf0,
+	0x17, 0x20, 0xfb, 0x9b, 0x14, 0xdf, 0x8d, 0x33, 0xb0, 0x68, 0xe3, 0x2a, 0x37, 0xe6, 0xb8, 0x7a,
+	0xc0, 0x7e, 0xca, 0xb2, 0x54, 0xd8, 0x5e, 0x8c, 0x4f, 0x65, 0x7e, 0x2f, 0xc7, 0xa7, 0xb2, 0x60,
+	0xe3, 0xee, 0x22, 0xd6, 0x26, 0xb1, 0x46, 0x6f, 0x27, 0xdc, 0x0d, 0x49, 0xdb, 0x34, 0xb3, 0x8a,
+	0x4e, 0x61, 0x3b, 0xbc, 0x19, 0x70, 0xa2, 0xd2, 0xcf, 0x2c, 0x1e, 0xe5, 0xee, 0x6a, 0x20, 0xe1,
+	0x7a, 0x0c, 0x19, 0x7f, 0x74, 0xf6, 0xd6, 0x78, 0x5e, 0xe3, 0x7d, 0x2e, 0x7a, 0x2c, 0xcb, 0x68,
+	0x17, 0xe1, 0x23, 0xc8, 0xf0, 0xb7, 0x01, 0xc7, 0x4e, 0x4e, 0xf8, 0x09, 0x59, 0xc6, 0x8e, 0xfd,
+	0x27, 0x17, 0x2f, 0xd4, 0x8d, 0xbf, 0x5e, 0xa8, 0x1b, 0xdf, 0x5d, 0xaa, 0xe8, 0xe2, 0x52, 0x45,
+	0x7f, 0x5e, 0xaa, 0xe8, 0x9f, 0x4b, 0x15, 0x3d, 0xf9, 0x78, 0xdd, 0xbf, 0x76, 0xf7, 0x84, 0xd8,
+	0x94, 0xb9, 0xaf, 0xbd, 0xff, 0x02, 0x00, 0x00, 0xff, 0xff, 0xec, 0xfe, 0xb2, 0x1f, 0x25, 0x0e,
+	0x00, 0x00,
 }
 
 // Reference imports to suppress errors if they are not otherwise used.
@@ -3078,7 +3075,7 @@ func (m *Info) Unmarshal(dAtA []byte) error {
 			if postIndex > l {
 				return io.ErrUnexpectedEOF
 			}
-			m.Digest = github_com_opencontainers_go_digest.Digest(dAtA[iNdEx:postIndex])
+			m.Digest = string(dAtA[iNdEx:postIndex])
 			iNdEx = postIndex
 		case 2:
 			if wireType != 0 {
@@ -3373,7 +3370,7 @@ func (m *InfoRequest) Unmarshal(dAtA []byte) error {
 			if postIndex > l {
 				return io.ErrUnexpectedEOF
 			}
-			m.Digest = github_com_opencontainers_go_digest.Digest(dAtA[iNdEx:postIndex])
+			m.Digest = string(dAtA[iNdEx:postIndex])
 			iNdEx = postIndex
 		default:
 			iNdEx = preIndex
@@ -3912,7 +3909,7 @@ func (m *DeleteContentRequest) Unmarshal(dAtA []byte) error {
 			if postIndex > l {
 				return io.ErrUnexpectedEOF
 			}
-			m.Digest = github_com_opencontainers_go_digest.Digest(dAtA[iNdEx:postIndex])
+			m.Digest = string(dAtA[iNdEx:postIndex])
 			iNdEx = postIndex
 		default:
 			iNdEx = preIndex
@@ -3995,7 +3992,7 @@ func (m *ReadContentRequest) Unmarshal(dAtA []byte) error {
 			if postIndex > l {
 				return io.ErrUnexpectedEOF
 			}
-			m.Digest = github_com_opencontainers_go_digest.Digest(dAtA[iNdEx:postIndex])
+			m.Digest = string(dAtA[iNdEx:postIndex])
 			iNdEx = postIndex
 		case 2:
 			if wireType != 0 {
@@ -4356,7 +4353,7 @@ func (m *Status) Unmarshal(dAtA []byte) error {
 			if postIndex > l {
 				return io.ErrUnexpectedEOF
 			}
-			m.Expected = github_com_opencontainers_go_digest.Digest(dAtA[iNdEx:postIndex])
+			m.Expected = string(dAtA[iNdEx:postIndex])
 			iNdEx = postIndex
 		default:
 			iNdEx = preIndex
@@ -4847,7 +4844,7 @@ func (m *WriteContentRequest) Unmarshal(dAtA []byte) error {
 			if postIndex > l {
 				return io.ErrUnexpectedEOF
 			}
-			m.Expected = github_com_opencontainers_go_digest.Digest(dAtA[iNdEx:postIndex])
+			m.Expected = string(dAtA[iNdEx:postIndex])
 			iNdEx = postIndex
 		case 5:
 			if wireType != 0 {
@@ -5233,7 +5230,7 @@ func (m *WriteContentResponse) Unmarshal(dAtA []byte) error {
 			if postIndex > l {
 				return io.ErrUnexpectedEOF
 			}
-			m.Digest = github_com_opencontainers_go_digest.Digest(dAtA[iNdEx:postIndex])
+			m.Digest = string(dAtA[iNdEx:postIndex])
 			iNdEx = postIndex
 		default:
 			iNdEx = preIndex
diff --git a/api/services/content/v1/content.proto b/api/services/content/v1/content.proto
index 2c61251e0..a8555633d 100644
--- a/api/services/content/v1/content.proto
+++ b/api/services/content/v1/content.proto
@@ -92,7 +92,7 @@ service Content {
 
 message Info {
 	// Digest is the hash identity of the blob.
-	string digest = 1 [(gogoproto.customtype) = "github.com/opencontainers/go-digest.Digest", (gogoproto.nullable) = false];
+	string digest = 1;
 
 	// Size is the total number of bytes in the blob.
 	int64 size = 2;
@@ -110,7 +110,7 @@ message Info {
 }
 
 message InfoRequest {
-	string digest = 1 [(gogoproto.customtype) = "github.com/opencontainers/go-digest.Digest", (gogoproto.nullable) = false];
+	string digest = 1;
 }
 
 message InfoResponse {
@@ -153,14 +153,14 @@ message ListContentResponse {
 
 message DeleteContentRequest {
 	// Digest specifies which content to delete.
-	string digest = 1 [(gogoproto.customtype) = "github.com/opencontainers/go-digest.Digest", (gogoproto.nullable) = false];
+	string digest = 1;
 }
 
 // ReadContentRequest defines the fields that make up a request to read a portion of
 // data from a stored object.
 message ReadContentRequest {
 	// Digest is the hash identity to read.
-	string digest = 1 [(gogoproto.customtype) = "github.com/opencontainers/go-digest.Digest", (gogoproto.nullable) = false];
+	string digest = 1;
 
 	// Offset specifies the number of bytes from the start at which to begin
 	// the read. If zero or less, the read will be from the start. This uses
@@ -184,7 +184,7 @@ message Status {
 	string ref = 3;
 	int64 offset = 4;
 	int64 total = 5;
-	string expected = 6 [(gogoproto.customtype) = "github.com/opencontainers/go-digest.Digest", (gogoproto.nullable) = false];
+	string expected = 6;
 }
 
 
@@ -269,7 +269,7 @@ message WriteContentRequest {
 	// Only the latest version will be used to check the content against the
 	// digest. It is only required to include it on a single message, before or
 	// with the commit action message.
-	string expected = 4 [(gogoproto.customtype) = "github.com/opencontainers/go-digest.Digest", (gogoproto.nullable) = false];
+	string expected = 4;
 
 	// Offset specifies the number of bytes from the start at which to begin
 	// the write. For most implementations, this means from the start of the
@@ -326,7 +326,7 @@ message WriteContentResponse {
 	// Digest, if present, includes the digest up to the currently committed
 	// bytes. If action is commit, this field will be set. It is implementation
 	// defined if this is set for other actions.
-	string digest = 6 [(gogoproto.customtype) = "github.com/opencontainers/go-digest.Digest", (gogoproto.nullable) = false];
+	string digest = 6;
 }
 
 message AbortRequest {
diff --git a/api/services/tasks/v1/tasks.pb.go b/api/services/tasks/v1/tasks.pb.go
index 92d6edc96..b9df0d9d0 100644
--- a/api/services/tasks/v1/tasks.pb.go
+++ b/api/services/tasks/v1/tasks.pb.go
@@ -13,7 +13,6 @@ import (
 	github_com_gogo_protobuf_sortkeys "github.com/gogo/protobuf/sortkeys"
 	github_com_gogo_protobuf_types "github.com/gogo/protobuf/types"
 	types1 "github.com/gogo/protobuf/types"
-	github_com_opencontainers_go_digest "github.com/opencontainers/go-digest"
 	grpc "google.golang.org/grpc"
 	codes "google.golang.org/grpc/codes"
 	status "google.golang.org/grpc/status"
@@ -857,12 +856,12 @@ func (m *ListPidsResponse) XXX_DiscardUnknown() {
 var xxx_messageInfo_ListPidsResponse proto.InternalMessageInfo
 
 type CheckpointTaskRequest struct {
-	ContainerID          string                                     `protobuf:"bytes,1,opt,name=container_id,json=containerId,proto3" json:"container_id,omitempty"`
-	ParentCheckpoint     github_com_opencontainers_go_digest.Digest `protobuf:"bytes,2,opt,name=parent_checkpoint,json=parentCheckpoint,proto3,customtype=github.com/opencontainers/go-digest.Digest" json:"parent_checkpoint"`
-	Options              *types1.Any                                `protobuf:"bytes,3,opt,name=options,proto3" json:"options,omitempty"`
-	XXX_NoUnkeyedLiteral struct{}                                   `json:"-"`
-	XXX_unrecognized     []byte                                     `json:"-"`
-	XXX_sizecache        int32                                      `json:"-"`
+	ContainerID          string      `protobuf:"bytes,1,opt,name=container_id,json=containerId,proto3" json:"container_id,omitempty"`
+	ParentCheckpoint     string      `protobuf:"bytes,2,opt,name=parent_checkpoint,json=parentCheckpoint,proto3" json:"parent_checkpoint,omitempty"`
+	Options              *types1.Any `protobuf:"bytes,3,opt,name=options,proto3" json:"options,omitempty"`
+	XXX_NoUnkeyedLiteral struct{}    `json:"-"`
+	XXX_unrecognized     []byte      `json:"-"`
+	XXX_sizecache        int32       `json:"-"`
 }
 
 func (m *CheckpointTaskRequest) Reset()      { *m = CheckpointTaskRequest{} }
@@ -1171,95 +1170,93 @@ func init() {
 }
 
 var fileDescriptor_310e7127b8a26f14 = []byte{
-	// 1399 bytes of a gzipped FileDescriptorProto
-	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0xbc, 0x58, 0x5b, 0x6f, 0x13, 0xc7,
-	0x17, 0x67, 0x7d, 0xf7, 0x71, 0x02, 0xc9, 0xfe, 0x43, 0xfe, 0xee, 0x16, 0xc5, 0x61, 0xfb, 0xe2,
-	0xa6, 0x65, 0x5d, 0x4c, 0x85, 0x10, 0x20, 0xd4, 0xdc, 0x1a, 0x59, 0x2d, 0x22, 0x2c, 0xf4, 0x22,
-	0xa4, 0xca, 0xdd, 0x78, 0x27, 0xf6, 0x28, 0xf6, 0xce, 0xb2, 0x33, 0x0e, 0xb8, 0x2f, 0xed, 0x47,
-	0xe0, 0xb5, 0x2f, 0xed, 0xd7, 0xe1, 0xb1, 0x8f, 0x55, 0x85, 0xd2, 0xe2, 0xd7, 0x7e, 0x82, 0xbe,
-	0x55, 0x73, 0xd9, 0xf5, 0xc6, 0x8e, 0x2f, 0x49, 0x48, 0x5f, 0x60, 0x66, 0xf6, 0x9c, 0x33, 0x67,
-	0x7e, 0xe7, 0xf6, 0x73, 0x60, 0xa3, 0x89, 0x59, 0xab, 0xbb, 0x67, 0x35, 0x48, 0xa7, 0xd2, 0x20,
-	0x1e, 0x73, 0xb0, 0x87, 0x02, 0x37, 0xbe, 0x74, 0x7c, 0x5c, 0xa1, 0x28, 0x38, 0xc4, 0x0d, 0x44,
-	0x2b, 0xcc, 0xa1, 0x07, 0xb4, 0x72, 0x78, 0x53, 0x2e, 0x2c, 0x3f, 0x20, 0x8c, 0xe8, 0xd7, 0x06,
-	0xd2, 0x56, 0x28, 0x69, 0x49, 0x81, 0xc3, 0x9b, 0xc6, 0xfb, 0x4d, 0x42, 0x9a, 0x6d, 0x54, 0x11,
-	0xb2, 0x7b, 0xdd, 0xfd, 0x0a, 0xea, 0xf8, 0xac, 0x27, 0x55, 0x8d, 0xf7, 0x86, 0x3f, 0x3a, 0x5e,
-	0xf8, 0x69, 0xa9, 0x49, 0x9a, 0x44, 0x2c, 0x2b, 0x7c, 0xa5, 0x4e, 0x6f, 0xcf, 0xe4, 0x2f, 0xeb,
-	0xf9, 0x88, 0x56, 0x3a, 0xa4, 0xeb, 0x31, 0xa5, 0x77, 0xe7, 0x34, 0x7a, 0x88, 0x05, 0xb8, 0xa1,
-	0x5e, 0x67, 0xdc, 0x3b, 0x85, 0xa6, 0x8b, 0x68, 0x23, 0xc0, 0x3e, 0x23, 0x81, 0x52, 0xbe, 0x7b,
-	0x0a, 0x65, 0x8e, 0x98, 0xf8, 0x47, 0xe9, 0x96, 0x86, 0xb1, 0x61, 0xb8, 0x83, 0x28, 0x73, 0x3a,
-	0xbe, 0x14, 0x30, 0xff, 0x4e, 0xc0, 0xe2, 0x66, 0x80, 0x1c, 0x86, 0x9e, 0x3a, 0xf4, 0xc0, 0x46,
-	0xcf, 0xbb, 0x88, 0x32, 0xbd, 0x0a, 0x73, 0x91, 0xf9, 0x3a, 0x76, 0x8b, 0xda, 0xaa, 0x56, 0xce,
-	0x6f, 0x5c, 0xe9, 0x1f, 0x95, 0x0a, 0x9b, 0xe1, 0x79, 0x6d, 0xcb, 0x2e, 0x44, 0x42, 0x35, 0x57,
-	0xaf, 0x40, 0x26, 0x20, 0x84, 0xed, 0xd3, 0x62, 0x72, 0x35, 0x59, 0x2e, 0x54, 0xff, 0x6f, 0xc5,
-	0x42, 0x2a, 0xbc, 0xb3, 0x1e, 0x72, 0x30, 0x6d, 0x25, 0xa6, 0x2f, 0x41, 0x9a, 0x32, 0x17, 0x7b,
-	0xc5, 0x14, 0xb7, 0x6e, 0xcb, 0x8d, 0xbe, 0x0c, 0x19, 0xca, 0x5c, 0xd2, 0x65, 0xc5, 0xb4, 0x38,
-	0x56, 0x3b, 0x75, 0x8e, 0x82, 0xa0, 0x98, 0x89, 0xce, 0x51, 0x10, 0xe8, 0x06, 0xe4, 0x18, 0x0a,
-	0x3a, 0xd8, 0x73, 0xda, 0xc5, 0xec, 0xaa, 0x56, 0xce, 0xd9, 0xd1, 0x5e, 0xbf, 0x0f, 0xd0, 0x68,
-	0xa1, 0xc6, 0x81, 0x4f, 0xb0, 0xc7, 0x8a, 0xb9, 0x55, 0xad, 0x5c, 0xa8, 0x5e, 0x1b, 0x75, 0x6b,
-	0x2b, 0x42, 0xdc, 0x8e, 0xc9, 0xeb, 0x16, 0x64, 0x89, 0xcf, 0x30, 0xf1, 0x68, 0x31, 0x2f, 0x54,
-	0x97, 0x2c, 0x89, 0xa6, 0x15, 0xa2, 0x69, 0xad, 0x7b, 0x3d, 0x3b, 0x14, 0xd2, 0xaf, 0xc3, 0x5c,
-	0xd0, 0xf5, 0x38, 0xc0, 0x75, 0xdf, 0x61, 0xad, 0x22, 0x08, 0x3f, 0x0b, 0xea, 0x6c, 0xd7, 0x61,
-	0x2d, 0xf3, 0x19, 0xe8, 0x71, 0xb0, 0xa9, 0x4f, 0x3c, 0x8a, 0xce, 0x84, 0xf6, 0x02, 0x24, 0x7d,
-	0xec, 0x16, 0x13, 0xab, 0x5a, 0x79, 0xde, 0xe6, 0x4b, 0xb3, 0x09, 0x73, 0x4f, 0x98, 0x13, 0xb0,
-	0xf3, 0xc4, 0xf0, 0x03, 0xc8, 0xa2, 0x97, 0xa8, 0x51, 0x57, 0x96, 0xf3, 0x1b, 0xd0, 0x3f, 0x2a,
-	0x65, 0xb6, 0x5f, 0xa2, 0x46, 0x6d, 0xcb, 0xce, 0xf0, 0x4f, 0x35, 0xd7, 0xbc, 0x0e, 0xf3, 0xea,
-	0x22, 0xe5, 0xbf, 0xf2, 0x45, 0x1b, 0xf8, 0xb2, 0x03, 0x8b, 0x5b, 0xa8, 0x8d, 0xce, 0x9d, 0x54,
-	0xe6, 0x2f, 0x1a, 0x5c, 0x96, 0x96, 0xa2, 0xdb, 0x96, 0x21, 0x11, 0x29, 0x67, 0xfa, 0x47, 0xa5,
-	0x44, 0x6d, 0xcb, 0x4e, 0xe0, 0x13, 0x10, 0xd1, 0x4b, 0x50, 0x40, 0x2f, 0x31, 0xab, 0x53, 0xe6,
-	0xb0, 0x2e, 0x4f, 0x4b, 0xfe, 0x05, 0xf8, 0xd1, 0x13, 0x71, 0xa2, 0xaf, 0x43, 0x9e, 0xef, 0x90,
-	0x5b, 0x77, 0x98, 0xc8, 0xc2, 0x42, 0xd5, 0x18, 0x89, 0xf1, 0xd3, 0xb0, 0x62, 0x36, 0x72, 0xaf,
-	0x8f, 0x4a, 0x97, 0x5e, 0xfd, 0x59, 0xd2, 0xec, 0x9c, 0x54, 0x5b, 0x67, 0x26, 0x81, 0x25, 0xe9,
-	0xdf, 0x6e, 0x40, 0x1a, 0x88, 0xd2, 0x0b, 0x47, 0x1f, 0x01, 0xec, 0xa0, 0x8b, 0x0f, 0xf2, 0x36,
-	0x14, 0xc4, 0x35, 0x0a, 0xf4, 0xdb, 0x90, 0xf5, 0xe5, 0x03, 0xc5, 0x15, 0x43, 0x65, 0x74, 0x78,
-	0x53, 0x55, 0x52, 0x08, 0x42, 0x28, 0x6c, 0xae, 0xc1, 0xc2, 0x97, 0x98, 0x32, 0x9e, 0x06, 0x11,
-	0x34, 0xcb, 0x90, 0xd9, 0xc7, 0x6d, 0x86, 0x02, 0xe9, 0xad, 0xad, 0x76, 0x3c, 0x69, 0x62, 0xb2,
-	0x51, 0x6d, 0xa4, 0xc5, 0x14, 0x28, 0x6a, 0xa2, 0xa9, 0x4c, 0xbe, 0x56, 0x8a, 0x9a, 0xaf, 0x34,
-	0x28, 0x7c, 0x81, 0xdb, 0xed, 0x8b, 0x06, 0x49, 0xf4, 0x24, 0xdc, 0xe4, 0x9d, 0x47, 0xe6, 0x96,
-	0xda, 0xf1, 0x54, 0x74, 0xda, 0x6d, 0x91, 0x51, 0x39, 0x9b, 0x2f, 0xcd, 0x7f, 0x34, 0xd0, 0xb9,
-	0xf2, 0x3b, 0xc8, 0x92, 0xa8, 0x6d, 0x26, 0x4e, 0x6e, 0x9b, 0xc9, 0x31, 0x6d, 0x33, 0x35, 0xb6,
-	0x6d, 0xa6, 0x87, 0xda, 0x66, 0x19, 0x52, 0xd4, 0x47, 0x0d, 0xd1, 0x68, 0xc7, 0x75, 0x3d, 0x21,
-	0x11, 0x47, 0x29, 0x3b, 0x36, 0x95, 0xae, 0xc2, 0xff, 0x8e, 0x3d, 0x5d, 0x46, 0xd6, 0xfc, 0x59,
-	0x83, 0x05, 0x1b, 0x51, 0xfc, 0x03, 0xda, 0x65, 0xbd, 0x0b, 0x0f, 0xd5, 0x12, 0xa4, 0x5f, 0x60,
-	0x97, 0xb5, 0x54, 0xa4, 0xe4, 0x86, 0xa3, 0xd3, 0x42, 0xb8, 0xd9, 0x92, 0xd5, 0x3f, 0x6f, 0xab,
-	0x9d, 0xf9, 0x23, 0x5c, 0xde, 0x6c, 0x13, 0x8a, 0x6a, 0x8f, 0xfe, 0x0b, 0xc7, 0x64, 0x38, 0x93,
-	0x22, 0x0a, 0x72, 0x63, 0x7e, 0x0e, 0x0b, 0xbb, 0x4e, 0x97, 0x9e, 0xbb, 0x7f, 0xee, 0xc0, 0xa2,
-	0x8d, 0x68, 0xb7, 0x73, 0x6e, 0x43, 0xdb, 0x70, 0x85, 0x17, 0xe7, 0x2e, 0x76, 0xcf, 0x93, 0xbc,
-	0xa6, 0x2d, 0xfb, 0x81, 0x34, 0xa3, 0x4a, 0xfc, 0x01, 0xe4, 0x55, 0xbb, 0x40, 0x61, 0x99, 0xaf,
-	0x4e, 0x2a, 0xf3, 0x9a, 0xb7, 0x4f, 0xec, 0x81, 0x8a, 0xf9, 0x46, 0x83, 0xab, 0x9b, 0xd1, 0xd8,
-	0x3e, 0x2f, 0x8d, 0xa9, 0xc3, 0xa2, 0xef, 0x04, 0xc8, 0x63, 0xf5, 0x18, 0x75, 0x90, 0xe1, 0xab,
-	0xf2, 0xfe, 0xff, 0xc7, 0x51, 0x69, 0x2d, 0x46, 0xc8, 0x88, 0x8f, 0xbc, 0x48, 0x9d, 0x56, 0x9a,
-	0xe4, 0x86, 0x8b, 0x9b, 0x88, 0x32, 0x6b, 0x4b, 0xfc, 0x67, 0x2f, 0x48, 0x63, 0x9b, 0x27, 0xd2,
-	0x8a, 0xe4, 0x0c, 0xb4, 0xc2, 0xfc, 0x16, 0x96, 0x87, 0x5f, 0x17, 0x01, 0x57, 0x18, 0x90, 0xc5,
-	0x13, 0x3b, 0xe4, 0x08, 0xbf, 0x89, 0x2b, 0x98, 0xbf, 0x26, 0x60, 0xf1, 0x2b, 0xdf, 0x7d, 0x07,
-	0xdc, 0xaf, 0x0a, 0xf9, 0x00, 0x51, 0xd2, 0x0d, 0x1a, 0x88, 0x0a, 0xb0, 0xc6, 0xbd, 0x6a, 0x20,
-	0xa6, 0xef, 0x41, 0xc1, 0xf1, 0x3c, 0xc2, 0x9c, 0x10, 0x0b, 0xee, 0xfd, 0x67, 0xd6, 0xa4, 0xdf,
-	0x01, 0xd6, 0x88, 0xb7, 0xd6, 0xfa, 0xc0, 0xc4, 0xb6, 0xc7, 0x82, 0x9e, 0x1d, 0x37, 0x6a, 0x3c,
-	0x80, 0x85, 0x61, 0x01, 0xde, 0x9c, 0x0f, 0x50, 0x4f, 0xcd, 0x1e, 0xbe, 0xe4, 0x25, 0x78, 0xe8,
-	0xb4, 0xbb, 0x28, 0xec, 0xa8, 0x62, 0x73, 0x37, 0x71, 0x47, 0x33, 0xd7, 0xe0, 0xf2, 0x43, 0x49,
-	0xe4, 0x43, 0x74, 0x8a, 0x90, 0x95, 0xe3, 0x4a, 0xe2, 0x9d, 0xb7, 0xc3, 0x2d, 0xaf, 0x90, 0x48,
-	0x36, 0x1a, 0x5e, 0x59, 0xf5, 0x3b, 0x40, 0x05, 0xa7, 0x78, 0x02, 0x27, 0x16, 0x02, 0x76, 0x28,
-	0x68, 0xee, 0x43, 0xe1, 0x1b, 0x07, 0x5f, 0xfc, 0x80, 0x0f, 0x60, 0x4e, 0xde, 0xa3, 0x7c, 0x1d,
-	0x22, 0x4b, 0xda, 0x64, 0xb2, 0x94, 0x38, 0x0b, 0x59, 0xaa, 0xbe, 0x99, 0x83, 0xb4, 0x18, 0xef,
-	0xfa, 0x01, 0x64, 0x24, 0x11, 0xd6, 0x2b, 0x93, 0x23, 0x3e, 0xf2, 0xdb, 0xc4, 0xf8, 0x64, 0x76,
-	0x05, 0xf5, 0xb4, 0xef, 0x21, 0x2d, 0x08, 0xab, 0xbe, 0x36, 0x59, 0x35, 0x4e, 0x9f, 0x8d, 0x8f,
-	0x66, 0x92, 0x55, 0x37, 0x34, 0x21, 0x23, 0x59, 0xe0, 0xb4, 0xe7, 0x8c, 0xb0, 0x62, 0xe3, 0xe3,
-	0x59, 0x14, 0xa2, 0x8b, 0x9e, 0xc3, 0xfc, 0x31, 0xba, 0xa9, 0x57, 0x67, 0x51, 0x3f, 0xce, 0x3a,
-	0x4e, 0x79, 0xe5, 0x33, 0x48, 0xee, 0x20, 0xa6, 0x97, 0x27, 0x2b, 0x0d, 0x38, 0xa9, 0xf1, 0xe1,
-	0x0c, 0x92, 0x11, 0x6e, 0x29, 0x3e, 0x0e, 0x74, 0x6b, 0xb2, 0xca, 0x30, 0x85, 0x34, 0x2a, 0x33,
-	0xcb, 0xab, 0x8b, 0x6a, 0x90, 0xe2, 0x8c, 0x50, 0x9f, 0xe2, 0x5b, 0x8c, 0x35, 0x1a, 0xcb, 0x23,
-	0xc9, 0xbd, 0xdd, 0xf1, 0x59, 0x4f, 0xdf, 0x85, 0x14, 0x2f, 0x25, 0x7d, 0x4a, 0x1e, 0x8e, 0xb2,
-	0xbd, 0xb1, 0x16, 0x9f, 0x40, 0x3e, 0x22, 0x42, 0xd3, 0xa0, 0x18, 0x66, 0x4c, 0x63, 0x8d, 0x3e,
-	0x82, 0xac, 0xa2, 0x30, 0xfa, 0x94, 0x78, 0x1f, 0x67, 0x3a, 0x13, 0x0c, 0xa6, 0x05, 0x25, 0x99,
-	0xe6, 0xe1, 0x30, 0x6f, 0x19, 0x6b, 0xf0, 0x31, 0x64, 0x24, 0x37, 0x99, 0x56, 0x34, 0x23, 0x0c,
-	0x66, 0xac, 0x49, 0x0c, 0xb9, 0x90, 0x5e, 0xe8, 0x37, 0xa6, 0xe7, 0x48, 0x8c, 0xcd, 0x18, 0xd6,
-	0xac, 0xe2, 0x2a, 0xa3, 0x5e, 0x00, 0xc4, 0x86, 0xfa, 0xad, 0x29, 0x10, 0x9f, 0x44, 0x4f, 0x8c,
-	0x4f, 0x4f, 0xa7, 0xa4, 0x2e, 0x7e, 0x0c, 0x19, 0x39, 0x06, 0xa7, 0xc1, 0x36, 0x32, 0x2c, 0xc7,
-	0xc2, 0xb6, 0x0f, 0x59, 0x35, 0xba, 0xa6, 0xe5, 0xca, 0xf1, 0x69, 0x68, 0xdc, 0x98, 0x51, 0x5a,
-	0xb9, 0xfe, 0x1d, 0xa4, 0xf8, 0xcc, 0x99, 0x56, 0x85, 0xb1, 0xf9, 0x67, 0xac, 0xcd, 0x22, 0x2a,
-	0xcd, 0x6f, 0x7c, 0xfd, 0xfa, 0xed, 0xca, 0xa5, 0xdf, 0xdf, 0xae, 0x5c, 0xfa, 0xa9, 0xbf, 0xa2,
-	0xbd, 0xee, 0xaf, 0x68, 0xbf, 0xf5, 0x57, 0xb4, 0xbf, 0xfa, 0x2b, 0xda, 0xb3, 0xfb, 0x67, 0xfb,
-	0x0b, 0xe5, 0x3d, 0xb1, 0xd8, 0xcb, 0x08, 0xb8, 0x6e, 0xfd, 0x1b, 0x00, 0x00, 0xff, 0xff, 0xe7,
-	0x74, 0x70, 0xb7, 0xe8, 0x14, 0x00, 0x00,
+	// 1372 bytes of a gzipped FileDescriptorProto
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0xbc, 0x58, 0xcb, 0x6e, 0xdb, 0x46,
+	0x17, 0x0e, 0x75, 0xd7, 0x91, 0x9d, 0xd8, 0xf3, 0x3b, 0xfe, 0x59, 0x36, 0xb0, 0x1c, 0x76, 0xa3,
+	0x3a, 0x0d, 0xd5, 0x28, 0x45, 0x10, 0x24, 0x41, 0x50, 0xdf, 0x6a, 0x08, 0x6d, 0x10, 0x87, 0x49,
+	0x2f, 0x08, 0x50, 0xb8, 0xb4, 0x34, 0x96, 0x06, 0x96, 0x48, 0x86, 0x33, 0x72, 0xa2, 0x6e, 0xda,
+	0x47, 0xc8, 0xb6, 0x9b, 0x76, 0xdb, 0x47, 0xc9, 0xb2, 0xcb, 0x2e, 0x0a, 0xb7, 0xd1, 0xb6, 0x4f,
+	0xd0, 0x5d, 0x31, 0x17, 0x52, 0xb4, 0x64, 0x5d, 0x6c, 0xc5, 0xdd, 0x18, 0x33, 0xc3, 0x73, 0xce,
+	0x9c, 0xf9, 0xce, 0xed, 0xb3, 0x60, 0xa3, 0x41, 0x58, 0xb3, 0xb3, 0x6f, 0xd5, 0xbc, 0x76, 0xb9,
+	0xe6, 0xb9, 0xcc, 0x21, 0x2e, 0x0e, 0xea, 0xf1, 0xa5, 0xe3, 0x93, 0x32, 0xc5, 0xc1, 0x11, 0xa9,
+	0x61, 0x5a, 0x66, 0x0e, 0x3d, 0xa4, 0xe5, 0xa3, 0x5b, 0x72, 0x61, 0xf9, 0x81, 0xc7, 0x3c, 0x74,
+	0xad, 0x2f, 0x6d, 0x85, 0x92, 0x96, 0x14, 0x38, 0xba, 0x65, 0xbc, 0xdf, 0xf0, 0xbc, 0x46, 0x0b,
+	0x97, 0x85, 0xec, 0x7e, 0xe7, 0xa0, 0x8c, 0xdb, 0x3e, 0xeb, 0x4a, 0x55, 0xe3, 0xbd, 0xc1, 0x8f,
+	0x8e, 0x1b, 0x7e, 0x5a, 0x6a, 0x78, 0x0d, 0x4f, 0x2c, 0xcb, 0x7c, 0xa5, 0x4e, 0xef, 0x4c, 0xe5,
+	0x2f, 0xeb, 0xfa, 0x98, 0x96, 0xdb, 0x5e, 0xc7, 0x65, 0x4a, 0xef, 0xee, 0x59, 0xf4, 0x30, 0x0b,
+	0x48, 0x4d, 0xbd, 0xce, 0xb8, 0x7f, 0x06, 0xcd, 0x3a, 0xa6, 0xb5, 0x80, 0xf8, 0xcc, 0x0b, 0x94,
+	0xf2, 0xbd, 0x33, 0x28, 0x73, 0xc4, 0xc4, 0x1f, 0xa5, 0x5b, 0x1c, 0xc4, 0x86, 0x91, 0x36, 0xa6,
+	0xcc, 0x69, 0xfb, 0x52, 0xc0, 0xfc, 0x3b, 0x01, 0x8b, 0x9b, 0x01, 0x76, 0x18, 0x7e, 0xe6, 0xd0,
+	0x43, 0x1b, 0xbf, 0xe8, 0x60, 0xca, 0x50, 0x05, 0xe6, 0x22, 0xf3, 0x7b, 0xa4, 0xae, 0x6b, 0xab,
+	0x5a, 0x29, 0xbf, 0x71, 0xa5, 0x77, 0x5c, 0x2c, 0x6c, 0x86, 0xe7, 0xd5, 0x2d, 0xbb, 0x10, 0x09,
+	0x55, 0xeb, 0xa8, 0x0c, 0x99, 0xc0, 0xf3, 0xd8, 0x01, 0xd5, 0x93, 0xab, 0xc9, 0x52, 0xa1, 0xf2,
+	0x7f, 0x2b, 0x16, 0x52, 0xe1, 0x9d, 0xf5, 0x88, 0x83, 0x69, 0x2b, 0x31, 0xb4, 0x04, 0x69, 0xca,
+	0xea, 0xc4, 0xd5, 0x53, 0xdc, 0xba, 0x2d, 0x37, 0x68, 0x19, 0x32, 0x94, 0xd5, 0xbd, 0x0e, 0xd3,
+	0xd3, 0xe2, 0x58, 0xed, 0xd4, 0x39, 0x0e, 0x02, 0x3d, 0x13, 0x9d, 0xe3, 0x20, 0x40, 0x06, 0xe4,
+	0x18, 0x0e, 0xda, 0xc4, 0x75, 0x5a, 0x7a, 0x76, 0x55, 0x2b, 0xe5, 0xec, 0x68, 0x8f, 0x1e, 0x00,
+	0xd4, 0x9a, 0xb8, 0x76, 0xe8, 0x7b, 0xc4, 0x65, 0x7a, 0x6e, 0x55, 0x2b, 0x15, 0x2a, 0xd7, 0x86,
+	0xdd, 0xda, 0x8a, 0x10, 0xb7, 0x63, 0xf2, 0xc8, 0x82, 0xac, 0xe7, 0x33, 0xe2, 0xb9, 0x54, 0xcf,
+	0x0b, 0xd5, 0x25, 0x4b, 0xa2, 0x69, 0x85, 0x68, 0x5a, 0xeb, 0x6e, 0xd7, 0x0e, 0x85, 0xd0, 0x75,
+	0x98, 0x0b, 0x3a, 0x2e, 0x07, 0x78, 0xcf, 0x77, 0x58, 0x53, 0x07, 0xe1, 0x67, 0x41, 0x9d, 0xed,
+	0x3a, 0xac, 0x69, 0x3e, 0x07, 0x14, 0x07, 0x9b, 0xfa, 0x9e, 0x4b, 0xf1, 0xb9, 0xd0, 0x5e, 0x80,
+	0xa4, 0x4f, 0xea, 0x7a, 0x62, 0x55, 0x2b, 0xcd, 0xdb, 0x7c, 0x69, 0x36, 0x60, 0xee, 0x29, 0x73,
+	0x02, 0x36, 0x4b, 0x0c, 0x3f, 0x80, 0x2c, 0x7e, 0x85, 0x6b, 0x7b, 0xca, 0x72, 0x7e, 0x03, 0x7a,
+	0xc7, 0xc5, 0xcc, 0xf6, 0x2b, 0x5c, 0xab, 0x6e, 0xd9, 0x19, 0xfe, 0xa9, 0x5a, 0x37, 0xaf, 0xc3,
+	0xbc, 0xba, 0x48, 0xf9, 0xaf, 0x7c, 0xd1, 0xfa, 0xbe, 0xec, 0xc0, 0xe2, 0x16, 0x6e, 0xe1, 0x99,
+	0x93, 0xca, 0xfc, 0x59, 0x83, 0xcb, 0xd2, 0x52, 0x74, 0xdb, 0x32, 0x24, 0x22, 0xe5, 0x4c, 0xef,
+	0xb8, 0x98, 0xa8, 0x6e, 0xd9, 0x09, 0x72, 0x0a, 0x22, 0xa8, 0x08, 0x05, 0xfc, 0x8a, 0xb0, 0x3d,
+	0xca, 0x1c, 0xd6, 0xe1, 0x69, 0xc9, 0xbf, 0x00, 0x3f, 0x7a, 0x2a, 0x4e, 0xd0, 0x3a, 0xe4, 0xf9,
+	0x0e, 0xd7, 0xf7, 0x1c, 0x26, 0xb2, 0xb0, 0x50, 0x31, 0x86, 0x62, 0xfc, 0x2c, 0xac, 0x98, 0x8d,
+	0xdc, 0x9b, 0xe3, 0xe2, 0xa5, 0xd7, 0x7f, 0x16, 0x35, 0x3b, 0x27, 0xd5, 0xd6, 0x99, 0xe9, 0xc1,
+	0x92, 0xf4, 0x6f, 0x37, 0xf0, 0x6a, 0x98, 0xd2, 0x0b, 0x47, 0x1f, 0x03, 0xec, 0xe0, 0x8b, 0x0f,
+	0xf2, 0x36, 0x14, 0xc4, 0x35, 0x0a, 0xf4, 0x3b, 0x90, 0xf5, 0xe5, 0x03, 0xc5, 0x15, 0x03, 0x65,
+	0x74, 0x74, 0x4b, 0x55, 0x52, 0x08, 0x42, 0x28, 0x6c, 0xae, 0xc1, 0xc2, 0x17, 0x84, 0x32, 0x9e,
+	0x06, 0x11, 0x34, 0xcb, 0x90, 0x39, 0x20, 0x2d, 0x86, 0x03, 0xe9, 0xad, 0xad, 0x76, 0x3c, 0x69,
+	0x62, 0xb2, 0x51, 0x6d, 0xa4, 0xc5, 0x14, 0xd0, 0x35, 0xd1, 0x54, 0xc6, 0x5f, 0x2b, 0x45, 0xcd,
+	0xd7, 0x1a, 0x14, 0x3e, 0x27, 0xad, 0xd6, 0x45, 0x83, 0x24, 0x7a, 0x12, 0x69, 0xf0, 0xce, 0x23,
+	0x73, 0x4b, 0xed, 0x78, 0x2a, 0x3a, 0xad, 0x96, 0xc8, 0xa8, 0x9c, 0xcd, 0x97, 0xe6, 0x3f, 0x1a,
+	0x20, 0xae, 0xfc, 0x0e, 0xb2, 0x24, 0x6a, 0x9b, 0x89, 0xd3, 0xdb, 0x66, 0x72, 0x44, 0xdb, 0x4c,
+	0x8d, 0x6c, 0x9b, 0xe9, 0x81, 0xb6, 0x59, 0x82, 0x14, 0xf5, 0x71, 0x4d, 0x34, 0xda, 0x51, 0x5d,
+	0x4f, 0x48, 0xc4, 0x51, 0xca, 0x8e, 0x4c, 0xa5, 0xab, 0xf0, 0xbf, 0x13, 0x4f, 0x97, 0x91, 0x35,
+	0x7f, 0xd2, 0x60, 0xc1, 0xc6, 0x94, 0x7c, 0x8f, 0x77, 0x59, 0xf7, 0xc2, 0x43, 0xb5, 0x04, 0xe9,
+	0x97, 0xa4, 0xce, 0x9a, 0x2a, 0x52, 0x72, 0xc3, 0xd1, 0x69, 0x62, 0xd2, 0x68, 0xca, 0xea, 0x9f,
+	0xb7, 0xd5, 0xce, 0xfc, 0x01, 0x2e, 0x6f, 0xb6, 0x3c, 0x8a, 0xab, 0x8f, 0xff, 0x0b, 0xc7, 0x64,
+	0x38, 0x93, 0x22, 0x0a, 0x72, 0x63, 0x7e, 0x06, 0x0b, 0xbb, 0x4e, 0x87, 0xce, 0xdc, 0x3f, 0x77,
+	0x60, 0xd1, 0xc6, 0xb4, 0xd3, 0x9e, 0xd9, 0xd0, 0x36, 0x5c, 0xe1, 0xc5, 0xb9, 0x4b, 0xea, 0xb3,
+	0x24, 0xaf, 0x69, 0xcb, 0x7e, 0x20, 0xcd, 0xa8, 0x12, 0x7f, 0x08, 0x79, 0xd5, 0x2e, 0x70, 0x58,
+	0xe6, 0xab, 0xe3, 0xca, 0xbc, 0xea, 0x1e, 0x78, 0x76, 0x5f, 0xc5, 0xfc, 0x55, 0x83, 0xab, 0x9b,
+	0xd1, 0xd8, 0x9e, 0x95, 0xc6, 0xdc, 0x80, 0x45, 0xdf, 0x09, 0xb0, 0xcb, 0xf6, 0x62, 0xd4, 0x41,
+	0x96, 0xda, 0x82, 0xfc, 0xb0, 0x79, 0x2a, 0x45, 0x48, 0x4e, 0x41, 0x11, 0xcc, 0x6f, 0x60, 0x79,
+	0xd0, 0xd3, 0x08, 0x84, 0x42, 0x9f, 0xf8, 0x9d, 0xda, 0xed, 0x86, 0xb8, 0x4a, 0x5c, 0xc1, 0xfc,
+	0x25, 0x01, 0x8b, 0x5f, 0xfa, 0xf5, 0x77, 0xc0, 0xe3, 0x2a, 0x90, 0x0f, 0x30, 0xf5, 0x3a, 0x41,
+	0x0d, 0x53, 0xf1, 0xf0, 0x51, 0xaf, 0xea, 0x8b, 0xa1, 0x7d, 0x28, 0x38, 0xae, 0xeb, 0x31, 0x27,
+	0xc4, 0x82, 0x7b, 0xff, 0xa9, 0x35, 0x8e, 0xd3, 0x5b, 0x43, 0xde, 0x5a, 0xeb, 0x7d, 0x13, 0xdb,
+	0x2e, 0x0b, 0xba, 0x76, 0xdc, 0xa8, 0xf1, 0x10, 0x16, 0x06, 0x05, 0x78, 0xa3, 0x3d, 0xc4, 0x5d,
+	0x35, 0x47, 0xf8, 0x92, 0x97, 0xd3, 0x91, 0xd3, 0xea, 0xe0, 0xb0, 0x3b, 0x8a, 0xcd, 0xbd, 0xc4,
+	0x5d, 0xcd, 0x5c, 0x83, 0xcb, 0x8f, 0x24, 0x29, 0x0f, 0xd1, 0xd1, 0x21, 0x2b, 0x47, 0x8f, 0xc4,
+	0x3b, 0x6f, 0x87, 0x5b, 0x9e, 0xed, 0x91, 0x6c, 0x34, 0x88, 0xb2, 0x8a, 0xd3, 0xab, 0xe0, 0xe8,
+	0xa7, 0xf0, 0x5b, 0x21, 0x60, 0x87, 0x82, 0xe6, 0x01, 0x14, 0xbe, 0x76, 0xc8, 0xc5, 0x0f, 0xeb,
+	0x00, 0xe6, 0xe4, 0x3d, 0xca, 0xd7, 0x01, 0xe2, 0xa3, 0x8d, 0x27, 0x3e, 0x89, 0xf3, 0x10, 0x9f,
+	0xca, 0x1f, 0x73, 0x90, 0x16, 0xa3, 0x1a, 0x1d, 0x42, 0x46, 0x92, 0x5a, 0x54, 0x1e, 0x1f, 0xf1,
+	0xa1, 0xff, 0x33, 0x8c, 0x8f, 0xa7, 0x57, 0x50, 0x4f, 0xfb, 0x0e, 0xd2, 0x82, 0x7c, 0xa2, 0xb5,
+	0xf1, 0xaa, 0x71, 0x2a, 0x6c, 0xdc, 0x98, 0x4a, 0x56, 0xdd, 0xd0, 0x80, 0x8c, 0x64, 0x74, 0x93,
+	0x9e, 0x33, 0xc4, 0x70, 0x8d, 0x8f, 0xa6, 0x51, 0x88, 0x2e, 0x7a, 0x01, 0xf3, 0x27, 0xa8, 0x23,
+	0xaa, 0x4c, 0xa3, 0x7e, 0x92, 0x41, 0x9c, 0xf1, 0xca, 0xe7, 0x90, 0xdc, 0xc1, 0x0c, 0x95, 0xc6,
+	0x2b, 0xf5, 0xf9, 0xa5, 0xf1, 0xe1, 0x14, 0x92, 0x11, 0x6e, 0x29, 0xde, 0xda, 0x91, 0x35, 0x5e,
+	0x65, 0x90, 0x0e, 0x1a, 0xe5, 0xa9, 0xe5, 0xd5, 0x45, 0x55, 0x48, 0x71, 0x76, 0x87, 0x26, 0xf8,
+	0x16, 0x63, 0x80, 0xc6, 0xf2, 0x50, 0x72, 0x6f, 0xb7, 0x7d, 0xd6, 0x45, 0xbb, 0x90, 0xe2, 0xa5,
+	0x84, 0x26, 0xe4, 0xe1, 0x30, 0x73, 0x1b, 0x69, 0xf1, 0x29, 0xe4, 0x23, 0x52, 0x33, 0x09, 0x8a,
+	0x41, 0xf6, 0x33, 0xd2, 0xe8, 0x63, 0xc8, 0x2a, 0x3a, 0x82, 0x26, 0xc4, 0xfb, 0x24, 0x6b, 0x19,
+	0x63, 0x30, 0x2d, 0xe8, 0xc5, 0x24, 0x0f, 0x07, 0x39, 0xc8, 0x48, 0x83, 0x4f, 0x20, 0x23, 0x79,
+	0xc6, 0xa4, 0xa2, 0x19, 0x62, 0x23, 0x23, 0x4d, 0x12, 0xc8, 0x85, 0x54, 0x01, 0xdd, 0x9c, 0x9c,
+	0x23, 0x31, 0x66, 0x62, 0x58, 0xd3, 0x8a, 0xab, 0x8c, 0x7a, 0x09, 0x10, 0x1b, 0xea, 0xb7, 0x27,
+	0x40, 0x7c, 0x1a, 0xd5, 0x30, 0x3e, 0x39, 0x9b, 0x92, 0xba, 0xf8, 0x09, 0x64, 0xe4, 0x18, 0x9c,
+	0x04, 0xdb, 0xd0, 0xb0, 0x1c, 0x09, 0xdb, 0x01, 0x64, 0xd5, 0xe8, 0x9a, 0x94, 0x2b, 0x27, 0xa7,
+	0xa1, 0x71, 0x73, 0x4a, 0x69, 0xe5, 0xfa, 0xb7, 0x90, 0xe2, 0x33, 0x67, 0x52, 0x15, 0xc6, 0xe6,
+	0x9f, 0xb1, 0x36, 0x8d, 0xa8, 0x34, 0xbf, 0xf1, 0xd5, 0x9b, 0xb7, 0x2b, 0x97, 0x7e, 0x7f, 0xbb,
+	0x72, 0xe9, 0xc7, 0xde, 0x8a, 0xf6, 0xa6, 0xb7, 0xa2, 0xfd, 0xd6, 0x5b, 0xd1, 0xfe, 0xea, 0xad,
+	0x68, 0xcf, 0x1f, 0x9c, 0xef, 0xd7, 0xc6, 0xfb, 0x62, 0xb1, 0x9f, 0x11, 0x70, 0xdd, 0xfe, 0x37,
+	0x00, 0x00, 0xff, 0xff, 0x1c, 0xab, 0x68, 0xe1, 0xb4, 0x14, 0x00, 0x00,
 }
 
 // Reference imports to suppress errors if they are not otherwise used.
@@ -6649,7 +6646,7 @@ func (m *CheckpointTaskRequest) Unmarshal(dAtA []byte) error {
 			if postIndex > l {
 				return io.ErrUnexpectedEOF
 			}
-			m.ParentCheckpoint = github_com_opencontainers_go_digest.Digest(dAtA[iNdEx:postIndex])
+			m.ParentCheckpoint = string(dAtA[iNdEx:postIndex])
 			iNdEx = postIndex
 		case 3:
 			if wireType != 2 {
diff --git a/api/services/tasks/v1/tasks.proto b/api/services/tasks/v1/tasks.proto
index 94c253be6..8a8616c8e 100644
--- a/api/services/tasks/v1/tasks.proto
+++ b/api/services/tasks/v1/tasks.proto
@@ -195,7 +195,7 @@ message ListPidsResponse {
 
 message CheckpointTaskRequest {
 	string container_id = 1;
-	string parent_checkpoint = 2 [(gogoproto.customtype) = "github.com/opencontainers/go-digest.Digest", (gogoproto.nullable) = false];
+	string parent_checkpoint = 2;
 	google.protobuf.Any options = 3;
 }
 
diff --git a/api/types/descriptor.pb.go b/api/types/descriptor.pb.go
index 12a1bf76c..d53e4e540 100644
--- a/api/types/descriptor.pb.go
+++ b/api/types/descriptor.pb.go
@@ -8,7 +8,6 @@ import (
 	_ "github.com/gogo/protobuf/gogoproto"
 	proto "github.com/gogo/protobuf/proto"
 	github_com_gogo_protobuf_sortkeys "github.com/gogo/protobuf/sortkeys"
-	github_com_opencontainers_go_digest "github.com/opencontainers/go-digest"
 	io "io"
 	math "math"
 	math_bits "math/bits"
@@ -33,13 +32,13 @@ const _ = proto.GoGoProtoPackageIsVersion3 // please upgrade the proto package
 // oci descriptor found in a manifest.
 // See https://godoc.org/github.com/opencontainers/image-spec/specs-go/v1#Descriptor
 type Descriptor struct {
-	MediaType            string                                     `protobuf:"bytes,1,opt,name=media_type,json=mediaType,proto3" json:"media_type,omitempty"`
-	Digest               github_com_opencontainers_go_digest.Digest `protobuf:"bytes,2,opt,name=digest,proto3,customtype=github.com/opencontainers/go-digest.Digest" json:"digest"`
-	Size_                int64                                      `protobuf:"varint,3,opt,name=size,proto3" json:"size,omitempty"`
-	Annotations          map[string]string                          `protobuf:"bytes,5,rep,name=annotations,proto3" json:"annotations,omitempty" protobuf_key:"bytes,1,opt,name=key,proto3" protobuf_val:"bytes,2,opt,name=value,proto3"`
-	XXX_NoUnkeyedLiteral struct{}                                   `json:"-"`
-	XXX_unrecognized     []byte                                     `json:"-"`
-	XXX_sizecache        int32                                      `json:"-"`
+	MediaType            string            `protobuf:"bytes,1,opt,name=media_type,json=mediaType,proto3" json:"media_type,omitempty"`
+	Digest               string            `protobuf:"bytes,2,opt,name=digest,proto3" json:"digest,omitempty"`
+	Size_                int64             `protobuf:"varint,3,opt,name=size,proto3" json:"size,omitempty"`
+	Annotations          map[string]string `protobuf:"bytes,5,rep,name=annotations,proto3" json:"annotations,omitempty" protobuf_key:"bytes,1,opt,name=key,proto3" protobuf_val:"bytes,2,opt,name=value,proto3"`
+	XXX_NoUnkeyedLiteral struct{}          `json:"-"`
+	XXX_unrecognized     []byte            `json:"-"`
+	XXX_sizecache        int32             `json:"-"`
 }
 
 func (m *Descriptor) Reset()      { *m = Descriptor{} }
@@ -84,27 +83,25 @@ func init() {
 }
 
 var fileDescriptor_37f958df3707db9e = []byte{
-	// 309 bytes of a gzipped FileDescriptorProto
+	// 277 bytes of a gzipped FileDescriptorProto
 	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0xe2, 0xb2, 0x4e, 0xcf, 0x2c, 0xc9,
 	0x28, 0x4d, 0xd2, 0x4b, 0xce, 0xcf, 0xd5, 0x4f, 0xce, 0xcf, 0x2b, 0x49, 0xcc, 0xcc, 0x4b, 0x2d,
 	0x4a, 0x41, 0x66, 0x26, 0x16, 0x64, 0xea, 0x97, 0x54, 0x16, 0xa4, 0x16, 0xeb, 0xa7, 0xa4, 0x16,
 	0x27, 0x17, 0x65, 0x16, 0x94, 0xe4, 0x17, 0xe9, 0x15, 0x14, 0xe5, 0x97, 0xe4, 0x0b, 0x09, 0x20,
 	0x94, 0xe9, 0x81, 0x95, 0x48, 0x89, 0xa4, 0xe7, 0xa7, 0xe7, 0x83, 0x25, 0xf5, 0x41, 0x2c, 0x88,
-	0x3a, 0xa5, 0x39, 0x4c, 0x5c, 0x5c, 0x2e, 0x70, 0xcd, 0x42, 0xb2, 0x5c, 0x5c, 0xb9, 0xa9, 0x29,
+	0x3a, 0xa5, 0x17, 0x8c, 0x5c, 0x5c, 0x2e, 0x70, 0xcd, 0x42, 0xb2, 0x5c, 0x5c, 0xb9, 0xa9, 0x29,
 	0x99, 0x89, 0xf1, 0x20, 0x3d, 0x12, 0x8c, 0x0a, 0x8c, 0x1a, 0x9c, 0x41, 0x9c, 0x60, 0x91, 0x90,
-	0xca, 0x82, 0x54, 0x21, 0x2f, 0x2e, 0xb6, 0x94, 0xcc, 0xf4, 0xd4, 0xe2, 0x12, 0x09, 0x26, 0x90,
-	0x94, 0x93, 0xd1, 0x89, 0x7b, 0xf2, 0x0c, 0xb7, 0xee, 0xc9, 0x6b, 0x21, 0x39, 0x35, 0xbf, 0x20,
-	0x35, 0x0f, 0x6e, 0x79, 0xb1, 0x7e, 0x7a, 0xbe, 0x2e, 0x44, 0x8b, 0x9e, 0x0b, 0x98, 0x0a, 0x82,
-	0x9a, 0x20, 0x24, 0xc4, 0xc5, 0x52, 0x9c, 0x59, 0x95, 0x2a, 0xc1, 0xac, 0xc0, 0xa8, 0xc1, 0x1c,
-	0x04, 0x66, 0x0b, 0xf9, 0x73, 0x71, 0x27, 0xe6, 0xe5, 0xe5, 0x97, 0x24, 0x96, 0x64, 0xe6, 0xe7,
-	0x15, 0x4b, 0xb0, 0x2a, 0x30, 0x6b, 0x70, 0x1b, 0xe9, 0xea, 0xa1, 0xfb, 0x45, 0x0f, 0xe1, 0x62,
-	0x3d, 0x47, 0x84, 0x7a, 0xd7, 0xbc, 0x92, 0xa2, 0xca, 0x20, 0x64, 0x13, 0xa4, 0xec, 0xb8, 0x04,
-	0xd0, 0x15, 0x08, 0x09, 0x70, 0x31, 0x67, 0xa7, 0x56, 0x42, 0x3d, 0x07, 0x62, 0x0a, 0x89, 0x70,
-	0xb1, 0x96, 0x25, 0xe6, 0x94, 0xa6, 0x42, 0x7c, 0x15, 0x04, 0xe1, 0x58, 0x31, 0x59, 0x30, 0x3a,
-	0x79, 0x9d, 0x78, 0x28, 0xc7, 0x70, 0xe3, 0xa1, 0x1c, 0x43, 0xc3, 0x23, 0x39, 0xc6, 0x13, 0x8f,
-	0xe4, 0x18, 0x2f, 0x3c, 0x92, 0x63, 0x7c, 0xf0, 0x48, 0x8e, 0x31, 0xca, 0x80, 0xf8, 0xd8, 0xb1,
-	0x06, 0x93, 0x49, 0x6c, 0xe0, 0x10, 0x37, 0x06, 0x04, 0x00, 0x00, 0xff, 0xff, 0x81, 0x35, 0x34,
-	0x94, 0xd8, 0x01, 0x00, 0x00,
+	0xca, 0x82, 0x54, 0x21, 0x31, 0x2e, 0xb6, 0x94, 0xcc, 0xf4, 0xd4, 0xe2, 0x12, 0x09, 0x26, 0xb0,
+	0x14, 0x94, 0x27, 0x24, 0xc4, 0xc5, 0x52, 0x9c, 0x59, 0x95, 0x2a, 0xc1, 0xac, 0xc0, 0xa8, 0xc1,
+	0x1c, 0x04, 0x66, 0x0b, 0xf9, 0x73, 0x71, 0x27, 0xe6, 0xe5, 0xe5, 0x97, 0x24, 0x96, 0x64, 0xe6,
+	0xe7, 0x15, 0x4b, 0xb0, 0x2a, 0x30, 0x6b, 0x70, 0x1b, 0xe9, 0xea, 0xa1, 0xbb, 0x4b, 0x0f, 0x61,
+	0xbb, 0x9e, 0x23, 0x42, 0xbd, 0x6b, 0x5e, 0x49, 0x51, 0x65, 0x10, 0xb2, 0x09, 0x52, 0x76, 0x5c,
+	0x02, 0xe8, 0x0a, 0x84, 0x04, 0xb8, 0x98, 0xb3, 0x53, 0x2b, 0xa1, 0x0e, 0x05, 0x31, 0x85, 0x44,
+	0xb8, 0x58, 0xcb, 0x12, 0x73, 0x4a, 0x53, 0xa1, 0x2e, 0x84, 0x70, 0xac, 0x98, 0x2c, 0x18, 0x9d,
+	0xbc, 0x4e, 0x3c, 0x94, 0x63, 0xb8, 0xf1, 0x50, 0x8e, 0xa1, 0xe1, 0x91, 0x1c, 0xe3, 0x89, 0x47,
+	0x72, 0x8c, 0x17, 0x1e, 0xc9, 0x31, 0x3e, 0x78, 0x24, 0xc7, 0x18, 0x65, 0x40, 0x7c, 0x48, 0x5b,
+	0x83, 0xc9, 0x24, 0x36, 0x70, 0xe8, 0x19, 0x03, 0x02, 0x00, 0x00, 0xff, 0xff, 0xcf, 0x4e, 0xfb,
+	0xcb, 0xa4, 0x01, 0x00, 0x00,
 }
 
 func (m *Descriptor) Marshal() (dAtA []byte, err error) {
@@ -343,7 +340,7 @@ func (m *Descriptor) Unmarshal(dAtA []byte) error {
 			if postIndex > l {
 				return io.ErrUnexpectedEOF
 			}
-			m.Digest = github_com_opencontainers_go_digest.Digest(dAtA[iNdEx:postIndex])
+			m.Digest = string(dAtA[iNdEx:postIndex])
 			iNdEx = postIndex
 		case 3:
 			if wireType != 0 {
diff --git a/api/types/descriptor.proto b/api/types/descriptor.proto
index 97dbf1be6..e2e8301bb 100644
--- a/api/types/descriptor.proto
+++ b/api/types/descriptor.proto
@@ -29,7 +29,7 @@ option go_package = "github.com/containerd/containerd/api/types;types";
 // See https://godoc.org/github.com/opencontainers/image-spec/specs-go/v1#Descriptor
 message Descriptor {
 	string media_type = 1;
-	string digest = 2 [(gogoproto.customtype) = "github.com/opencontainers/go-digest.Digest", (gogoproto.nullable) = false];
+	string digest = 2;
 	int64 size = 3;
 	map<string, string> annotations = 5;
 }
diff --git a/container_checkpoint_opts.go b/container_checkpoint_opts.go
index a64ef618b..7515c0d86 100644
--- a/container_checkpoint_opts.go
+++ b/container_checkpoint_opts.go
@@ -31,6 +31,7 @@ import (
 	"github.com/containerd/containerd/rootfs"
 	"github.com/containerd/containerd/runtime/v2/runc/options"
 	"github.com/containerd/typeurl"
+	"github.com/opencontainers/go-digest"
 	imagespec "github.com/opencontainers/image-spec/specs-go/v1"
 )
 
@@ -72,7 +73,7 @@ func WithCheckpointTask(ctx context.Context, client *Client, c *containers.Conta
 		index.Manifests = append(index.Manifests, imagespec.Descriptor{
 			MediaType:   d.MediaType,
 			Size:        d.Size_,
-			Digest:      d.Digest,
+			Digest:      digest.Digest(d.Digest),
 			Platform:    &platformSpec,
 			Annotations: d.Annotations,
 		})
diff --git a/content/proxy/content_reader.go b/content/proxy/content_reader.go
index 2947a7c82..c8fa50827 100644
--- a/content/proxy/content_reader.go
+++ b/content/proxy/content_reader.go
@@ -36,7 +36,7 @@ func (ra *remoteReaderAt) Size() int64 {
 
 func (ra *remoteReaderAt) ReadAt(p []byte, off int64) (n int, err error) {
 	rr := &contentapi.ReadContentRequest{
-		Digest: ra.digest,
+		Digest: ra.digest.String(),
 		Offset: off,
 		Size_:  int64(len(p)),
 	}
diff --git a/content/proxy/content_store.go b/content/proxy/content_store.go
index 217b74651..def119a47 100644
--- a/content/proxy/content_store.go
+++ b/content/proxy/content_store.go
@@ -42,7 +42,7 @@ func NewContentStore(client contentapi.ContentClient) content.Store {
 
 func (pcs *proxyContentStore) Info(ctx context.Context, dgst digest.Digest) (content.Info, error) {
 	resp, err := pcs.client.Info(ctx, &contentapi.InfoRequest{
-		Digest: dgst,
+		Digest: dgst.String(),
 	})
 	if err != nil {
 		return content.Info{}, errdefs.FromGRPC(err)
@@ -81,7 +81,7 @@ func (pcs *proxyContentStore) Walk(ctx context.Context, fn content.WalkFunc, fil
 
 func (pcs *proxyContentStore) Delete(ctx context.Context, dgst digest.Digest) error {
 	if _, err := pcs.client.Delete(ctx, &contentapi.DeleteContentRequest{
-		Digest: dgst,
+		Digest: dgst.String(),
 	}); err != nil {
 		return errdefs.FromGRPC(err)
 	}
@@ -119,7 +119,7 @@ func (pcs *proxyContentStore) Status(ctx context.Context, ref string) (content.S
 		UpdatedAt: status.UpdatedAt,
 		Offset:    status.Offset,
 		Total:     status.Total,
-		Expected:  status.Expected,
+		Expected:  digest.Digest(status.Expected),
 	}, nil
 }
 
@@ -152,7 +152,7 @@ func (pcs *proxyContentStore) ListStatuses(ctx context.Context, filters ...strin
 			UpdatedAt: status.UpdatedAt,
 			Offset:    status.Offset,
 			Total:     status.Total,
-			Expected:  status.Expected,
+			Expected:  digest.Digest(status.Expected),
 		})
 	}
 
@@ -200,7 +200,7 @@ func (pcs *proxyContentStore) negotiate(ctx context.Context, ref string, size in
 		Action:   contentapi.WriteActionStat,
 		Ref:      ref,
 		Total:    size,
-		Expected: expected,
+		Expected: expected.String(),
 	}); err != nil {
 		return nil, 0, err
 	}
@@ -215,7 +215,7 @@ func (pcs *proxyContentStore) negotiate(ctx context.Context, ref string, size in
 
 func infoToGRPC(info content.Info) contentapi.Info {
 	return contentapi.Info{
-		Digest:    info.Digest,
+		Digest:    info.Digest.String(),
 		Size_:     info.Size,
 		CreatedAt: info.CreatedAt,
 		UpdatedAt: info.UpdatedAt,
@@ -225,7 +225,7 @@ func infoToGRPC(info content.Info) contentapi.Info {
 
 func infoFromGRPC(info contentapi.Info) content.Info {
 	return content.Info{
-		Digest:    info.Digest,
+		Digest:    digest.Digest(info.Digest),
 		Size:      info.Size_,
 		CreatedAt: info.CreatedAt,
 		UpdatedAt: info.UpdatedAt,
diff --git a/content/proxy/content_writer.go b/content/proxy/content_writer.go
index ffc0f50ea..c1d9fd6f8 100644
--- a/content/proxy/content_writer.go
+++ b/content/proxy/content_writer.go
@@ -45,7 +45,7 @@ func (rw *remoteWriter) send(req *contentapi.WriteContentRequest) (*contentapi.W
 	if err == nil {
 		// try to keep these in sync
 		if resp.Digest != "" {
-			rw.digest = resp.Digest
+			rw.digest = digest.Digest(resp.Digest)
 		}
 	}
 
@@ -92,7 +92,7 @@ func (rw *remoteWriter) Write(p []byte) (n int, err error) {
 
 	rw.offset += int64(n)
 	if resp.Digest != "" {
-		rw.digest = resp.Digest
+		rw.digest = digest.Digest(resp.Digest)
 	}
 	return
 }
@@ -115,7 +115,7 @@ func (rw *remoteWriter) Commit(ctx context.Context, size int64, expected digest.
 		Action:   contentapi.WriteActionCommit,
 		Total:    size,
 		Offset:   rw.offset,
-		Expected: expected,
+		Expected: expected.String(),
 		Labels:   base.Labels,
 	})
 	if err != nil {
@@ -126,11 +126,12 @@ func (rw *remoteWriter) Commit(ctx context.Context, size int64, expected digest.
 		return fmt.Errorf("unexpected size: %v != %v", resp.Offset, size)
 	}
 
-	if expected != "" && resp.Digest != expected {
+	actual := digest.Digest(resp.Digest)
+	if expected != "" && actual != expected {
 		return fmt.Errorf("unexpected digest: %v != %v", resp.Digest, expected)
 	}
 
-	rw.digest = resp.Digest
+	rw.digest = actual
 	rw.offset = resp.Offset
 	return nil
 }
diff --git a/diff.go b/diff.go
index 445df0192..c9871c0bd 100644
--- a/diff.go
+++ b/diff.go
@@ -24,6 +24,7 @@ import (
 	"github.com/containerd/containerd/diff"
 	"github.com/containerd/containerd/errdefs"
 	"github.com/containerd/containerd/mount"
+	"github.com/opencontainers/go-digest"
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 )
 
@@ -88,7 +89,7 @@ func (r *diffRemote) Compare(ctx context.Context, a, b []mount.Mount, opts ...di
 func toDescriptor(d *types.Descriptor) ocispec.Descriptor {
 	return ocispec.Descriptor{
 		MediaType:   d.MediaType,
-		Digest:      d.Digest,
+		Digest:      digest.Digest(d.Digest),
 		Size:        d.Size_,
 		Annotations: d.Annotations,
 	}
@@ -97,7 +98,7 @@ func toDescriptor(d *types.Descriptor) ocispec.Descriptor {
 func fromDescriptor(d ocispec.Descriptor) *types.Descriptor {
 	return &types.Descriptor{
 		MediaType:   d.MediaType,
-		Digest:      d.Digest,
+		Digest:      d.Digest.String(),
 		Size_:       d.Size,
 		Annotations: d.Annotations,
 	}
diff --git a/image_store.go b/image_store.go
index a9702822a..37e792a60 100644
--- a/image_store.go
+++ b/image_store.go
@@ -24,6 +24,7 @@ import (
 	"github.com/containerd/containerd/errdefs"
 	"github.com/containerd/containerd/images"
 	ptypes "github.com/gogo/protobuf/types"
+	"github.com/opencontainers/go-digest"
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 )
 
@@ -140,7 +141,7 @@ func descFromProto(desc *types.Descriptor) ocispec.Descriptor {
 	return ocispec.Descriptor{
 		MediaType:   desc.MediaType,
 		Size:        desc.Size_,
-		Digest:      desc.Digest,
+		Digest:      digest.Digest(desc.Digest),
 		Annotations: desc.Annotations,
 	}
 }
@@ -149,7 +150,7 @@ func descToProto(desc *ocispec.Descriptor) types.Descriptor {
 	return types.Descriptor{
 		MediaType:   desc.MediaType,
 		Size_:       desc.Size,
-		Digest:      desc.Digest,
+		Digest:      desc.Digest.String(),
 		Annotations: desc.Annotations,
 	}
 }
diff --git a/services/content/contentserver/contentserver.go b/services/content/contentserver/contentserver.go
index eb5855a47..d5d417f0d 100644
--- a/services/content/contentserver/contentserver.go
+++ b/services/content/contentserver/contentserver.go
@@ -57,11 +57,12 @@ func (s *service) Register(server *grpc.Server) error {
 }
 
 func (s *service) Info(ctx context.Context, req *api.InfoRequest) (*api.InfoResponse, error) {
-	if err := req.Digest.Validate(); err != nil {
+	dg, err := digest.Parse(req.Digest)
+	if err != nil {
 		return nil, status.Errorf(codes.InvalidArgument, "%q failed validation", req.Digest)
 	}
 
-	bi, err := s.store.Info(ctx, req.Digest)
+	bi, err := s.store.Info(ctx, dg)
 	if err != nil {
 		return nil, errdefs.ToGRPC(err)
 	}
@@ -72,7 +73,8 @@ func (s *service) Info(ctx context.Context, req *api.InfoRequest) (*api.InfoResp
 }
 
 func (s *service) Update(ctx context.Context, req *api.UpdateRequest) (*api.UpdateResponse, error) {
-	if err := req.Info.Digest.Validate(); err != nil {
+	_, err := digest.Parse(req.Info.Digest)
+	if err != nil {
 		return nil, status.Errorf(codes.InvalidArgument, "%q failed validation", req.Info.Digest)
 	}
 
@@ -99,7 +101,7 @@ func (s *service) List(req *api.ListContentRequest, session api.Content_ListServ
 
 	if err := s.store.Walk(session.Context(), func(info content.Info) error {
 		buffer = append(buffer, api.Info{
-			Digest:    info.Digest,
+			Digest:    info.Digest.String(),
 			Size_:     info.Size,
 			CreatedAt: info.CreatedAt,
 			Labels:    info.Labels,
@@ -130,11 +132,12 @@ func (s *service) List(req *api.ListContentRequest, session api.Content_ListServ
 
 func (s *service) Delete(ctx context.Context, req *api.DeleteContentRequest) (*ptypes.Empty, error) {
 	log.G(ctx).WithField("digest", req.Digest).Debugf("delete content")
-	if err := req.Digest.Validate(); err != nil {
+	dg, err := digest.Parse(req.Digest)
+	if err != nil {
 		return nil, status.Errorf(codes.InvalidArgument, err.Error())
 	}
 
-	if err := s.store.Delete(ctx, req.Digest); err != nil {
+	if err := s.store.Delete(ctx, dg); err != nil {
 		return nil, errdefs.ToGRPC(err)
 	}
 
@@ -142,16 +145,17 @@ func (s *service) Delete(ctx context.Context, req *api.DeleteContentRequest) (*p
 }
 
 func (s *service) Read(req *api.ReadContentRequest, session api.Content_ReadServer) error {
-	if err := req.Digest.Validate(); err != nil {
+	dg, err := digest.Parse(req.Digest)
+	if err != nil {
 		return status.Errorf(codes.InvalidArgument, "%v: %v", req.Digest, err)
 	}
 
-	oi, err := s.store.Info(session.Context(), req.Digest)
+	oi, err := s.store.Info(session.Context(), dg)
 	if err != nil {
 		return errdefs.ToGRPC(err)
 	}
 
-	ra, err := s.store.ReaderAt(session.Context(), ocispec.Descriptor{Digest: req.Digest})
+	ra, err := s.store.ReaderAt(session.Context(), ocispec.Descriptor{Digest: dg})
 	if err != nil {
 		return errdefs.ToGRPC(err)
 	}
@@ -221,7 +225,7 @@ func (s *service) Status(ctx context.Context, req *api.StatusRequest) (*api.Stat
 		Ref:       status.Ref,
 		Offset:    status.Offset,
 		Total:     status.Total,
-		Expected:  status.Expected,
+		Expected:  status.Expected.String(),
 	}
 
 	return &resp, nil
@@ -241,7 +245,7 @@ func (s *service) ListStatuses(ctx context.Context, req *api.ListStatusesRequest
 			Ref:       status.Ref,
 			Offset:    status.Offset,
 			Total:     status.Total,
-			Expected:  status.Expected,
+			Expected:  status.Expected.String(),
 		})
 	}
 
@@ -293,7 +297,7 @@ func (s *service) Write(session api.Content_WriteServer) (err error) {
 		"ref": ref,
 	}
 	total = req.Total
-	expected = req.Expected
+	expected = digest.Digest(req.Expected)
 	if total > 0 {
 		fields["total"] = total
 	}
@@ -341,12 +345,13 @@ func (s *service) Write(session api.Content_WriteServer) (err error) {
 		// Supporting these two paths is quite awkward but it lets both API
 		// users use the same writer style for each with a minimum of overhead.
 		if req.Expected != "" {
-			if expected != "" && expected != req.Expected {
-				log.G(ctx).Debugf("commit digest differs from writer digest: %v != %v", req.Expected, expected)
+			dg := digest.Digest(req.Expected)
+			if expected != "" && expected != dg {
+				log.G(ctx).Debugf("commit digest differs from writer digest: %v != %v", dg, expected)
 			}
-			expected = req.Expected
+			expected = dg
 
-			if _, err := s.store.Info(session.Context(), req.Expected); err == nil {
+			if _, err := s.store.Info(session.Context(), dg); err == nil {
 				if err := wr.Close(); err != nil {
 					log.G(ctx).WithError(err).Error("failed to close writer")
 				}
@@ -369,7 +374,7 @@ func (s *service) Write(session api.Content_WriteServer) (err error) {
 
 		switch req.Action {
 		case api.WriteActionStat:
-			msg.Digest = wr.Digest()
+			msg.Digest = wr.Digest().String()
 			msg.StartedAt = ws.StartedAt
 			msg.UpdatedAt = ws.UpdatedAt
 			msg.Total = total
@@ -416,7 +421,7 @@ func (s *service) Write(session api.Content_WriteServer) (err error) {
 				}
 			}
 
-			msg.Digest = wr.Digest()
+			msg.Digest = wr.Digest().String()
 		}
 
 		if err := session.Send(&msg); err != nil {
@@ -448,7 +453,7 @@ func (s *service) Abort(ctx context.Context, req *api.AbortRequest) (*ptypes.Emp
 
 func infoToGRPC(info content.Info) api.Info {
 	return api.Info{
-		Digest:    info.Digest,
+		Digest:    info.Digest.String(),
 		Size_:     info.Size,
 		CreatedAt: info.CreatedAt,
 		UpdatedAt: info.UpdatedAt,
@@ -458,7 +463,7 @@ func infoToGRPC(info content.Info) api.Info {
 
 func infoFromGRPC(info api.Info) content.Info {
 	return content.Info{
-		Digest:    info.Digest,
+		Digest:    digest.Digest(info.Digest),
 		Size:      info.Size_,
 		CreatedAt: info.CreatedAt,
 		UpdatedAt: info.UpdatedAt,
diff --git a/services/content/store.go b/services/content/store.go
index 016cd0676..4d67af65e 100644
--- a/services/content/store.go
+++ b/services/content/store.go
@@ -71,6 +71,6 @@ func (s *store) Delete(ctx context.Context, dgst digest.Digest) error {
 	}
 	// TODO: Consider whether we should return error here.
 	return s.publisher.Publish(ctx, "/content/delete", &eventstypes.ContentDelete{
-		Digest: dgst,
+		Digest: dgst.String(),
 	})
 }
diff --git a/services/diff/local.go b/services/diff/local.go
index 7d0f07167..a1ad1e679 100644
--- a/services/diff/local.go
+++ b/services/diff/local.go
@@ -27,6 +27,7 @@ import (
 	"github.com/containerd/containerd/mount"
 	"github.com/containerd/containerd/plugin"
 	"github.com/containerd/containerd/services"
+	"github.com/opencontainers/go-digest"
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"google.golang.org/grpc"
 )
@@ -170,7 +171,7 @@ func toMounts(apim []*types.Mount) []mount.Mount {
 func toDescriptor(d *types.Descriptor) ocispec.Descriptor {
 	return ocispec.Descriptor{
 		MediaType:   d.MediaType,
-		Digest:      d.Digest,
+		Digest:      digest.Digest(d.Digest),
 		Size:        d.Size_,
 		Annotations: d.Annotations,
 	}
@@ -179,7 +180,7 @@ func toDescriptor(d *types.Descriptor) ocispec.Descriptor {
 func fromDescriptor(d ocispec.Descriptor) *types.Descriptor {
 	return &types.Descriptor{
 		MediaType:   d.MediaType,
-		Digest:      d.Digest,
+		Digest:      d.Digest.String(),
 		Size_:       d.Size,
 		Annotations: d.Annotations,
 	}
diff --git a/services/images/helpers.go b/services/images/helpers.go
index 6b7b008c0..724dd0358 100644
--- a/services/images/helpers.go
+++ b/services/images/helpers.go
@@ -20,6 +20,7 @@ import (
 	imagesapi "github.com/containerd/containerd/api/services/images/v1"
 	"github.com/containerd/containerd/api/types"
 	"github.com/containerd/containerd/images"
+	"github.com/opencontainers/go-digest"
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 )
 
@@ -58,7 +59,7 @@ func descFromProto(desc *types.Descriptor) ocispec.Descriptor {
 	return ocispec.Descriptor{
 		MediaType:   desc.MediaType,
 		Size:        desc.Size_,
-		Digest:      desc.Digest,
+		Digest:      digest.Digest(desc.Digest),
 		Annotations: desc.Annotations,
 	}
 }
@@ -67,7 +68,7 @@ func descToProto(desc *ocispec.Descriptor) types.Descriptor {
 	return types.Descriptor{
 		MediaType:   desc.MediaType,
 		Size_:       desc.Size,
-		Digest:      desc.Digest,
+		Digest:      desc.Digest.String(),
 		Annotations: desc.Annotations,
 	}
 }
diff --git a/services/tasks/local.go b/services/tasks/local.go
index 96ed36ca4..ec82a0681 100644
--- a/services/tasks/local.go
+++ b/services/tasks/local.go
@@ -47,6 +47,7 @@ import (
 	"github.com/containerd/containerd/services"
 	"github.com/containerd/typeurl"
 	ptypes "github.com/gogo/protobuf/types"
+	"github.com/opencontainers/go-digest"
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/codes"
@@ -173,7 +174,7 @@ func (l *local) Create(ctx context.Context, r *api.CreateTaskRequest, _ ...grpc.
 		}
 		reader, err := l.store.ReaderAt(ctx, ocispec.Descriptor{
 			MediaType:   r.Checkpoint.MediaType,
-			Digest:      r.Checkpoint.Digest,
+			Digest:      digest.Digest(r.Checkpoint.Digest),
 			Size:        r.Checkpoint.Size_,
 			Annotations: r.Checkpoint.Annotations,
 		})
@@ -688,7 +689,7 @@ func (l *local) writeContent(ctx context.Context, mediaType, ref string, r io.Re
 	}
 	return &types.Descriptor{
 		MediaType:   mediaType,
-		Digest:      writer.Digest(),
+		Digest:      writer.Digest().String(),
 		Size_:       size,
 		Annotations: make(map[string]string),
 	}, nil
diff --git a/task.go b/task.go
index 692d92c1d..aa9a45c96 100644
--- a/task.go
+++ b/task.go
@@ -444,7 +444,7 @@ func (t *task) Checkpoint(ctx context.Context, opts ...CheckpointTaskOpts) (Imag
 	if i.Name == "" {
 		i.Name = fmt.Sprintf(checkpointNameFormat, t.id, time.Now().Format(checkpointDateFormat))
 	}
-	request.ParentCheckpoint = i.ParentCheckpoint
+	request.ParentCheckpoint = i.ParentCheckpoint.String()
 	if i.Options != nil {
 		any, err := typeurl.MarshalAny(i.Options)
 		if err != nil {
@@ -604,7 +604,7 @@ func (t *task) checkpointTask(ctx context.Context, index *v1.Index, request *tas
 		index.Manifests = append(index.Manifests, v1.Descriptor{
 			MediaType: d.MediaType,
 			Size:      d.Size_,
-			Digest:    d.Digest,
+			Digest:    digest.Digest(d.Digest),
 			Platform: &v1.Platform{
 				OS:           goruntime.GOOS,
 				Architecture: goruntime.GOARCH,
diff --git a/task_opts.go b/task_opts.go
index 56f3cbad6..4315b212b 100644
--- a/task_opts.go
+++ b/task_opts.go
@@ -70,7 +70,7 @@ func WithTaskCheckpoint(im Image) NewTaskOpts {
 				info.Checkpoint = &types.Descriptor{
 					MediaType:   m.MediaType,
 					Size_:       m.Size,
-					Digest:      m.Digest,
+					Digest:      m.Digest.String(),
 					Annotations: m.Annotations,
 				}
 				return nil