diff --git a/image/config.go b/image/config.go
index 7ef0ac2..3ba66b5 100644
--- a/image/config.go
+++ b/image/config.go
@@ -33,9 +33,9 @@ import (
 
 type config v1.Image
 
-func findConfig(w walker, d *descriptor) (*config, error) {
+func findConfig(w walker, d *v1.Descriptor) (*config, error) {
 	var c config
-	cpath := filepath.Join("blobs", d.algo(), d.hash())
+	cpath := filepath.Join("blobs", string(d.Digest.Algorithm()), d.Digest.Hex())
 
 	switch err := w.walk(func(path string, info os.FileInfo, r io.Reader) error {
 		if info.IsDir() || filepath.Clean(path) != cpath {
diff --git a/image/descriptor.go b/image/descriptor.go
index cb7aa14..6d16fd6 100644
--- a/image/descriptor.go
+++ b/image/descriptor.go
@@ -20,33 +20,13 @@ import (
 	"io"
 	"os"
 	"path/filepath"
-	"strings"
 
-	"github.com/opencontainers/go-digest"
 	"github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/pkg/errors"
 )
 
-type descriptor v1.Descriptor
-
-func (d *descriptor) algo() string {
-	pts := strings.SplitN(string(d.Digest), ":", 2)
-	if len(pts) != 2 {
-		return ""
-	}
-	return pts[0]
-}
-
-func (d *descriptor) hash() string {
-	pts := strings.SplitN(string(d.Digest), ":", 2)
-	if len(pts) != 2 {
-		return ""
-	}
-	return pts[1]
-}
-
-func listReferences(w walker) (map[string]*descriptor, error) {
-	refs := make(map[string]*descriptor)
+func listReferences(w walker) (map[string]*v1.Descriptor, error) {
+	refs := make(map[string]*v1.Descriptor)
 	var index v1.ImageIndex
 
 	if err := w.walk(func(path string, info os.FileInfo, r io.Reader) error {
@@ -60,7 +40,7 @@ func listReferences(w walker) (map[string]*descriptor, error) {
 
 		for i := 0; i < len(index.Manifests); i++ {
 			if index.Manifests[i].Descriptor.Annotations["org.opencontainers.ref.name"] != "" {
-				refs[index.Manifests[i].Descriptor.Annotations["org.opencontainers.ref.name"]] = (*descriptor)(&index.Manifests[i].Descriptor)
+				refs[index.Manifests[i].Descriptor.Annotations["org.opencontainers.ref.name"]] = &index.Manifests[i].Descriptor
 			}
 		}
 
@@ -71,8 +51,8 @@ func listReferences(w walker) (map[string]*descriptor, error) {
 	return refs, nil
 }
 
-func findDescriptor(w walker, name string) (*descriptor, error) {
-	var d descriptor
+func findDescriptor(w walker, name string) (*v1.Descriptor, error) {
+	var d v1.Descriptor
 	var index v1.ImageIndex
 
 	switch err := w.walk(func(path string, info os.FileInfo, r io.Reader) error {
@@ -86,7 +66,7 @@ func findDescriptor(w walker, name string) (*descriptor, error) {
 
 		for i := 0; i < len(index.Manifests); i++ {
 			if index.Manifests[i].Descriptor.Annotations["org.opencontainers.ref.name"] == name {
-				d = (descriptor)(index.Manifests[i].Descriptor)
+				d = index.Manifests[i].Descriptor
 				return errEOW
 			}
 		}
@@ -102,7 +82,7 @@ func findDescriptor(w walker, name string) (*descriptor, error) {
 	}
 }
 
-func (d *descriptor) validate(w walker, mts []string) error {
+func validateDescriptor(d *v1.Descriptor, w walker, mts []string) error {
 	var found bool
 	for _, mt := range mts {
 		if d.MediaType == mt {
@@ -114,13 +94,12 @@ func (d *descriptor) validate(w walker, mts []string) error {
 		return fmt.Errorf("invalid descriptor MediaType %q", d.MediaType)
 	}
 
-	parsed, err := digest.Parse(string(d.Digest))
-	if err != nil {
+	if err := d.Digest.Validate(); err != nil {
 		return err
 	}
 
 	// Copy the contents of the layer in to the verifier
-	verifier := parsed.Verifier()
+	verifier := d.Digest.Verifier()
 	numBytes, err := w.get(*d, verifier)
 	if err != nil {
 		return err
diff --git a/image/image.go b/image/image.go
index 4ff345c..9318af1 100644
--- a/image/image.go
+++ b/image/image.go
@@ -84,7 +84,7 @@ func validate(w walker, refs []string, out *log.Logger) error {
 			return fmt.Errorf("reference %s not found", ref)
 		}
 
-		if err = d.validate(w, validRefMediaTypes); err != nil {
+		if err = validateDescriptor(d, w, validRefMediaTypes); err != nil {
 			return err
 		}
 
@@ -135,7 +135,7 @@ func unpack(w walker, dest, refName string) error {
 		return err
 	}
 
-	if err = ref.validate(w, validRefMediaTypes); err != nil {
+	if err = validateDescriptor(ref, w, validRefMediaTypes); err != nil {
 		return err
 	}
 
@@ -183,7 +183,7 @@ func createRuntimeBundle(w walker, dest, refName, rootfs string) error {
 		return err
 	}
 
-	if err = ref.validate(w, validRefMediaTypes); err != nil {
+	if err = validateDescriptor(ref, w, validRefMediaTypes); err != nil {
 		return err
 	}
 
diff --git a/image/image_test.go b/image/image_test.go
index a8182a5..e83440b 100644
--- a/image/image_test.go
+++ b/image/image_test.go
@@ -238,7 +238,7 @@ func createLayoutFile(root string) error {
 	return err
 }
 
-func createIndexFile(root string, mft descriptor) error {
+func createIndexFile(root string, mft v1.Descriptor) error {
 	indexpath := filepath.Join(root, "index.json")
 	f, err := os.Create(indexpath)
 	if err != nil {
@@ -251,48 +251,48 @@ func createIndexFile(root string, mft descriptor) error {
 	return err
 }
 
-func createManifestFile(root, str string) (descriptor, error) {
+func createManifestFile(root, str string) (v1.Descriptor, error) {
 	name := filepath.Join(root, "blobs", "sha256", "test-manifest")
 	f, err := os.Create(name)
 	if err != nil {
-		return descriptor{}, err
+		return v1.Descriptor{}, err
 	}
 	defer f.Close()
 
 	_, err = io.Copy(f, bytes.NewBuffer([]byte(str)))
 	if err != nil {
-		return descriptor{}, err
+		return v1.Descriptor{}, err
 	}
 
 	return createHashedBlob(name)
 }
 
-func createConfigFile(root, config string) (descriptor, error) {
+func createConfigFile(root, config string) (v1.Descriptor, error) {
 	name := filepath.Join(root, "blobs", "sha256", "test-config")
 	f, err := os.Create(name)
 	if err != nil {
-		return descriptor{}, err
+		return v1.Descriptor{}, err
 	}
 	defer f.Close()
 
 	_, err = io.Copy(f, bytes.NewBuffer([]byte(config)))
 	if err != nil {
-		return descriptor{}, err
+		return v1.Descriptor{}, err
 	}
 
 	return createHashedBlob(name)
 }
 
-func createImageLayerFile(root string, list []tarContent) (descriptor, error) {
+func createImageLayerFile(root string, list []tarContent) (v1.Descriptor, error) {
 	name := filepath.Join(root, "blobs", "sha256", "test-layer")
 	err := createTarBlob(name, list)
 	if err != nil {
-		return descriptor{}, err
+		return v1.Descriptor{}, err
 	}
 
 	desc, err := createHashedBlob(name)
 	if err != nil {
-		return descriptor{}, err
+		return v1.Descriptor{}, err
 	}
 
 	desc.MediaType = v1.MediaTypeImageLayer
@@ -321,40 +321,39 @@ func createTarBlob(name string, list []tarContent) error {
 	return nil
 }
 
-func createHashedBlob(name string) (descriptor, error) {
+func createHashedBlob(name string) (v1.Descriptor, error) {
 	desc, err := newDescriptor(name)
 	if err != nil {
-		return descriptor{}, err
+		return v1.Descriptor{}, err
 	}
 
-	parsed, err := digest.Parse(string(desc.Digest))
-	if err != nil {
-		return descriptor{}, err
+	if err := desc.Digest.Validate(); err != nil {
+		return v1.Descriptor{}, err
 	}
 
 	// Rename the file to hashed-digest name.
-	err = os.Rename(name, filepath.Join(filepath.Dir(name), parsed.Hex()))
+	err = os.Rename(name, filepath.Join(filepath.Dir(name), desc.Digest.Hex()))
 	if err != nil {
-		return descriptor{}, err
+		return v1.Descriptor{}, err
 	}
 
 	return desc, nil
 }
 
-func newDescriptor(name string) (descriptor, error) {
+func newDescriptor(name string) (v1.Descriptor, error) {
 	file, err := os.Open(name)
 	if err != nil {
-		return descriptor{}, err
+		return v1.Descriptor{}, err
 	}
 	defer file.Close()
 
 	digester := digest.SHA256.Digester()
 	size, err := io.Copy(digester.Hash(), file)
 	if err != nil {
-		return descriptor{}, err
+		return v1.Descriptor{}, err
 	}
 
-	return descriptor{
+	return v1.Descriptor{
 		Digest: digester.Digest(),
 		Size:   size,
 	}, nil
diff --git a/image/manifest.go b/image/manifest.go
index 8834c1e..a827ab6 100644
--- a/image/manifest.go
+++ b/image/manifest.go
@@ -36,13 +36,13 @@ import (
 )
 
 type manifest struct {
-	Config descriptor   `json:"config"`
-	Layers []descriptor `json:"layers"`
+	Config v1.Descriptor   `json:"config"`
+	Layers []v1.Descriptor `json:"layers"`
 }
 
-func findManifest(w walker, d *descriptor) (*manifest, error) {
+func findManifest(w walker, d *v1.Descriptor) (*manifest, error) {
 	var m manifest
-	mpath := filepath.Join("blobs", d.algo(), d.hash())
+	mpath := filepath.Join("blobs", string(d.Digest.Algorithm()), d.Digest.Hex())
 
 	switch err := w.walk(func(path string, info os.FileInfo, r io.Reader) error {
 		if info.IsDir() || filepath.Clean(path) != mpath {
@@ -74,7 +74,7 @@ func findManifest(w walker, d *descriptor) (*manifest, error) {
 }
 
 func (m *manifest) validate(w walker) error {
-	if err := m.Config.validate(w, []string{v1.MediaTypeImageConfig}); err != nil {
+	if err := validateDescriptor(&m.Config, w, []string{v1.MediaTypeImageConfig}); err != nil {
 		return errors.Wrap(err, "config validation failed")
 	}
 
@@ -86,7 +86,7 @@ func (m *manifest) validate(w walker) error {
 	}
 
 	for _, d := range m.Layers {
-		if err := d.validate(w, validLayerMediaTypes); err != nil {
+		if err := validateDescriptor(&d, w, validLayerMediaTypes); err != nil {
 			return errors.Wrap(err, "layer validation failed")
 		}
 	}
@@ -118,8 +118,8 @@ func (m *manifest) unpack(w walker, dest string) (retErr error) {
 				return nil
 			}
 
-			dd, err := filepath.Rel(filepath.Join("blobs", d.algo()), filepath.Clean(path))
-			if err != nil || d.hash() != dd {
+			dd, err := filepath.Rel(filepath.Join("blobs", string(d.Digest.Algorithm())), filepath.Clean(path))
+			if err != nil || d.Digest.Hex() != dd {
 				return nil
 			}
 
diff --git a/image/manifest_test.go b/image/manifest_test.go
index 1a6ee21..1657ad0 100644
--- a/image/manifest_test.go
+++ b/image/manifest_test.go
@@ -27,6 +27,7 @@ import (
 
 	"github.com/Sirupsen/logrus"
 	"github.com/opencontainers/go-digest"
+	"github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/pkg/errors"
 
 	bz2 "github.com/dsnet/compress/bzip2"
@@ -141,7 +142,7 @@ func testUnpackLayer(t *testing.T, compression string, invalid bool) {
 	}
 
 	testManifest := manifest{
-		Layers: []descriptor{descriptor{
+		Layers: []v1.Descriptor{v1.Descriptor{
 			MediaType: mediatype,
 			Digest:    digester.Digest(),
 		}},
@@ -210,7 +211,7 @@ func TestUnpackLayerRemovePartialyUnpackedFile(t *testing.T) {
 	}
 
 	testManifest := manifest{
-		Layers: []descriptor{descriptor{
+		Layers: []v1.Descriptor{v1.Descriptor{
 			MediaType: "application/vnd.oci.image.layer.v1.tar+gzip",
 			Digest:    digester.Digest(),
 		}},
diff --git a/image/walker.go b/image/walker.go
index 3ef5e8b..8bf369f 100644
--- a/image/walker.go
+++ b/image/walker.go
@@ -22,6 +22,7 @@ import (
 	"path/filepath"
 	"sync"
 
+	"github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/pkg/errors"
 )
 
@@ -40,7 +41,7 @@ type walker interface {
 
 	// get will copy an arbitrary blob, defined by desc, in to dst. returns
 	// the number of bytes copied on success.
-	get(desc descriptor, dst io.Writer) (int64, error)
+	get(desc v1.Descriptor, dst io.Writer) (int64, error)
 }
 
 // tarWalker exposes access to image layouts in a tar file.
@@ -87,11 +88,11 @@ loop:
 	return nil
 }
 
-func (w *tarWalker) get(desc descriptor, dst io.Writer) (int64, error) {
+func (w *tarWalker) get(desc v1.Descriptor, dst io.Writer) (int64, error) {
 	var bytes int64
 	done := false
 
-	expectedPath := filepath.Join("blobs", desc.algo(), desc.hash())
+	expectedPath := filepath.Join("blobs", string(desc.Digest.Algorithm()), desc.Digest.Hex())
 
 	f := func(path string, info os.FileInfo, rdr io.Reader) error {
 		var err error
@@ -161,8 +162,8 @@ func (w *pathWalker) walk(f walkFunc) error {
 	})
 }
 
-func (w *pathWalker) get(desc descriptor, dst io.Writer) (int64, error) {
-	name := filepath.Join(w.root, "blobs", desc.algo(), desc.hash())
+func (w *pathWalker) get(desc v1.Descriptor, dst io.Writer) (int64, error) {
+	name := filepath.Join(w.root, "blobs", string(desc.Digest.Algorithm()), desc.Digest.Hex())
 
 	info, err := os.Stat(name)
 	if err != nil {