@@ -27,18 +27,18 @@ func (daemon *Daemon) GetImageID(refOrID string) (image.ID, error) {

 		return "", err

 	}

 	if id != "" {

-		if _, err := daemon.imageStore.Get(image.ID(id)); err != nil {

+		if _, err := daemon.imageStore.Get(image.IDFromDigest(id)); err != nil {

 			return "", ErrImageDoesNotExist{refOrID}

 		}

-		return image.ID(id), nil

+		return image.IDFromDigest(id), nil

 	}

 	if id, err := daemon.referenceStore.Get(ref); err == nil {

-		return id, nil

+		return image.IDFromDigest(id), nil

 	}

 	if tagged, ok := ref.(reference.NamedTagged); ok {

 		if id, err := daemon.imageStore.Search(tagged.Tag()); err == nil {

-			for _, namedRef := range daemon.referenceStore.References(id) {

+			for _, namedRef := range daemon.referenceStore.References(id.Digest()) {

 				if namedRef.Name() == ref.Name() {

 					return id, nil

 				}

@@ -68,7 +68,7 @@ func (daemon *Daemon) ImageDelete(imageRef string, force, prune bool) ([]types.I

 		return nil, daemon.imageNotExistToErrcode(err)

 	}

-	repoRefs := daemon.referenceStore.References(imgID)

+	repoRefs := daemon.referenceStore.References(imgID.Digest())

 	var removedRepositoryRef bool

 	if !isImageIDPrefix(imgID.String(), imageRef) {

@@ -102,7 +102,7 @@ func (daemon *Daemon) ImageDelete(imageRef string, force, prune bool) ([]types.I

 		daemon.LogImageEvent(imgID.String(), imgID.String(), "untag")

 		records = append(records, untaggedRecord)

-		repoRefs = daemon.referenceStore.References(imgID)

+		repoRefs = daemon.referenceStore.References(imgID.Digest())

 		// If a tag reference was removed and the only remaining

 		// references to the same repository are digest references,

@@ -239,7 +239,7 @@ func (daemon *Daemon) removeImageRef(ref reference.Named) (reference.Named, erro

 // daemon's event service. An "Untagged" types.ImageDelete is added to the

 // given list of records.

 func (daemon *Daemon) removeAllReferencesToImageID(imgID image.ID, records *[]types.ImageDelete) error {

-	imageRefs := daemon.referenceStore.References(imgID)

+	imageRefs := daemon.referenceStore.References(imgID.Digest())

 	for _, imageRef := range imageRefs {

 		parsedRef, err := daemon.removeImageRef(imageRef)

@@ -372,7 +372,7 @@ func (daemon *Daemon) checkImageDeleteConflict(imgID image.ID, mask conflictType

 	}

 	// Check if any repository tags/digest reference this image.

-	if mask&conflictActiveReference != 0 && len(daemon.referenceStore.References(imgID)) > 0 {

+	if mask&conflictActiveReference != 0 && len(daemon.referenceStore.References(imgID.Digest())) > 0 {

 		return &imageDeleteConflict{

 			imgID:   imgID,

 			message: "image is referenced in multiple repositories",

@@ -400,5 +400,5 @@ func (daemon *Daemon) checkImageDeleteConflict(imgID image.ID, mask conflictType

 // that there are no repository references to the given image and it has no

 // child images.

 func (daemon *Daemon) imageIsDangling(imgID image.ID) bool {

-	return !(len(daemon.referenceStore.References(imgID)) > 0 || len(daemon.imageStore.Children(imgID)) > 0)

+	return !(len(daemon.referenceStore.References(imgID.Digest())) > 0 || len(daemon.imageStore.Children(imgID)) > 0)

 }

@@ -60,7 +60,7 @@ func (daemon *Daemon) ImageHistory(name string) ([]*types.ImageHistory, error) {

 		h.ID = id.String()

 		var tags []string

-		for _, r := range daemon.referenceStore.References(id) {

+		for _, r := range daemon.referenceStore.References(id.Digest()) {

 			if _, ok := r.(reference.NamedTagged); ok {

 				tags = append(tags, r.String())

 			}

@@ -17,7 +17,7 @@ func (daemon *Daemon) LookupImage(name string) (*types.ImageInspect, error) {

 		return nil, fmt.Errorf("No such image: %s", name)

 	}

-	refs := daemon.referenceStore.References(img.ID())

+	refs := daemon.referenceStore.References(img.ID().Digest())

 	repoTags := []string{}

 	repoDigests := []string{}

 	for _, ref := range refs {

@@ -28,7 +28,7 @@ func (daemon *Daemon) TagImage(imageName, repository, tag string) error {

 // TagImageWithReference adds the given reference to the image ID provided.

 func (daemon *Daemon) TagImageWithReference(imageID image.ID, newTag reference.Named) error {

-	if err := daemon.referenceStore.AddTag(newTag, imageID, true); err != nil {

+	if err := daemon.referenceStore.AddTag(newTag, imageID.Digest(), true); err != nil {

 		return err

 	}

@@ -135,7 +135,7 @@ func (daemon *Daemon) Images(filterArgs, filter string, all bool) ([]*types.Imag

 		newImage := newImage(img, size)

-		for _, ref := range daemon.referenceStore.References(id) {

+		for _, ref := range daemon.referenceStore.References(id.Digest()) {

 			if filter != "" { // filter by tag/repo name

 				if filterTagged { // filter by tag, require full ref match

 					if ref.String() != filter {

@@ -205,21 +205,21 @@ func ValidateRepoName(name string) error {

 	return nil

 }

-func addDigestReference(store reference.Store, ref reference.Named, dgst digest.Digest, imageID image.ID) error {

+func addDigestReference(store reference.Store, ref reference.Named, dgst digest.Digest, id digest.Digest) error {

 	dgstRef, err := reference.WithDigest(ref, dgst)

 	if err != nil {

 		return err

 	}

-	if oldTagImageID, err := store.Get(dgstRef); err == nil {

-		if oldTagImageID != imageID {

+	if oldTagID, err := store.Get(dgstRef); err == nil {

+		if oldTagID != id {

 			// Updating digests not supported by reference store

-			logrus.Errorf("Image ID for digest %s changed from %s to %s, cannot update", dgst.String(), oldTagImageID, imageID)

+			logrus.Errorf("Image ID for digest %s changed from %s to %s, cannot update", dgst.String(), oldTagID, id)

 		}

 		return nil

 	} else if err != reference.ErrDoesNotExist {

 		return err

 	}

-	return store.AddDigest(dgstRef, imageID, true)

+	return store.AddDigest(dgstRef, id, true)

 }

@@ -248,7 +248,7 @@ func (p *v1Puller) pullImage(ctx context.Context, v1ID, endpoint string, localNa

 		return err

 	}

-	if err := p.config.ReferenceStore.AddTag(localNameRef, imageID, true); err != nil {

+	if err := p.config.ReferenceStore.AddTag(localNameRef, imageID.Digest(), true); err != nil {

 		return err

 	}

@@ -374,23 +374,23 @@ func (p *v2Puller) pullV2Tag(ctx context.Context, ref reference.Named) (tagUpdat

 	progress.Message(p.config.ProgressOutput, tagOrDigest, "Pulling from "+p.repo.Named().Name())

 	var (

-		imageID        image.ID

+		id             digest.Digest

 		manifestDigest digest.Digest

 	)

 	switch v := manifest.(type) {

 	case *schema1.SignedManifest:

-		imageID, manifestDigest, err = p.pullSchema1(ctx, ref, v)

+		id, manifestDigest, err = p.pullSchema1(ctx, ref, v)

 		if err != nil {

 			return false, err

 		}

 	case *schema2.DeserializedManifest:

-		imageID, manifestDigest, err = p.pullSchema2(ctx, ref, v)

+		id, manifestDigest, err = p.pullSchema2(ctx, ref, v)

 		if err != nil {

 			return false, err

 		}

 	case *manifestlist.DeserializedManifestList:

-		imageID, manifestDigest, err = p.pullManifestList(ctx, ref, v)

+		id, manifestDigest, err = p.pullManifestList(ctx, ref, v)

 		if err != nil {

 			return false, err

 		}

@@ -400,31 +400,31 @@ func (p *v2Puller) pullV2Tag(ctx context.Context, ref reference.Named) (tagUpdat

 	progress.Message(p.config.ProgressOutput, "", "Digest: "+manifestDigest.String())

-	oldTagImageID, err := p.config.ReferenceStore.Get(ref)

+	oldTagID, err := p.config.ReferenceStore.Get(ref)

 	if err == nil {

-		if oldTagImageID == imageID {

-			return false, addDigestReference(p.config.ReferenceStore, ref, manifestDigest, imageID)

+		if oldTagID == id {

+			return false, addDigestReference(p.config.ReferenceStore, ref, manifestDigest, id)

 		}

 	} else if err != reference.ErrDoesNotExist {

 		return false, err

 	}

 	if canonical, ok := ref.(reference.Canonical); ok {

-		if err = p.config.ReferenceStore.AddDigest(canonical, imageID, true); err != nil {

+		if err = p.config.ReferenceStore.AddDigest(canonical, id, true); err != nil {

 			return false, err

 		}

 	} else {

-		if err = addDigestReference(p.config.ReferenceStore, ref, manifestDigest, imageID); err != nil {

+		if err = addDigestReference(p.config.ReferenceStore, ref, manifestDigest, id); err != nil {

 			return false, err

 		}

-		if err = p.config.ReferenceStore.AddTag(ref, imageID, true); err != nil {

+		if err = p.config.ReferenceStore.AddTag(ref, id, true); err != nil {

 			return false, err

 		}

 	}

 	return true, nil

 }

-func (p *v2Puller) pullSchema1(ctx context.Context, ref reference.Named, unverifiedManifest *schema1.SignedManifest) (imageID image.ID, manifestDigest digest.Digest, err error) {

+func (p *v2Puller) pullSchema1(ctx context.Context, ref reference.Named, unverifiedManifest *schema1.SignedManifest) (id digest.Digest, manifestDigest digest.Digest, err error) {

 	var verifiedManifest *schema1.Manifest

 	verifiedManifest, err = verifySchema1Manifest(unverifiedManifest, ref)

 	if err != nil {

@@ -487,28 +487,27 @@ func (p *v2Puller) pullSchema1(ctx context.Context, ref reference.Named, unverif

 		return "", "", err

 	}

-	imageID, err = p.config.ImageStore.Create(config)

+	imageID, err := p.config.ImageStore.Create(config)

 	if err != nil {

 		return "", "", err

 	}

 	manifestDigest = digest.FromBytes(unverifiedManifest.Canonical)

-	return imageID, manifestDigest, nil

+	return imageID.Digest(), manifestDigest, nil

 }

-func (p *v2Puller) pullSchema2(ctx context.Context, ref reference.Named, mfst *schema2.DeserializedManifest) (imageID image.ID, manifestDigest digest.Digest, err error) {

+func (p *v2Puller) pullSchema2(ctx context.Context, ref reference.Named, mfst *schema2.DeserializedManifest) (id digest.Digest, manifestDigest digest.Digest, err error) {

 	manifestDigest, err = schema2ManifestDigest(ref, mfst)

 	if err != nil {

 		return "", "", err

 	}

 	target := mfst.Target()

-	imageID = image.ID(target.Digest)

-	if _, err := p.config.ImageStore.Get(imageID); err == nil {

+	if _, err := p.config.ImageStore.Get(image.IDFromDigest(target.Digest)); err == nil {

 		// If the image already exists locally, no need to pull

 		// anything.

-		return imageID, manifestDigest, nil

+		return target.Digest, manifestDigest, nil

 	}

 	var descriptors []xfer.DownloadDescriptor

@@ -534,7 +533,7 @@ func (p *v2Puller) pullSchema2(ctx context.Context, ref reference.Named, mfst *s

 	// Pull the image config

 	go func() {

-		configJSON, err := p.pullSchema2ImageConfig(ctx, target.Digest)

+		configJSON, err := p.pullSchema2Config(ctx, target.Digest)

 		if err != nil {

 			errChan <- ImageConfigPullError{Err: err}

 			cancel()

@@ -618,12 +617,12 @@ func (p *v2Puller) pullSchema2(ctx context.Context, ref reference.Named, mfst *s

 		}

 	}

-	imageID, err = p.config.ImageStore.Create(configJSON)

+	imageID, err := p.config.ImageStore.Create(configJSON)

 	if err != nil {

 		return "", "", err

 	}

-	return imageID, manifestDigest, nil

+	return imageID.Digest(), manifestDigest, nil

 }

 func receiveConfig(configChan <-chan []byte, errChan <-chan error) ([]byte, image.Image, error) {

@@ -643,7 +642,7 @@ func receiveConfig(configChan <-chan []byte, errChan <-chan error) ([]byte, imag

 // pullManifestList handles "manifest lists" which point to various

 // platform-specifc manifests.

-func (p *v2Puller) pullManifestList(ctx context.Context, ref reference.Named, mfstList *manifestlist.DeserializedManifestList) (imageID image.ID, manifestListDigest digest.Digest, err error) {

+func (p *v2Puller) pullManifestList(ctx context.Context, ref reference.Named, mfstList *manifestlist.DeserializedManifestList) (id digest.Digest, manifestListDigest digest.Digest, err error) {

 	manifestListDigest, err = schema2ManifestDigest(ref, mfstList)

 	if err != nil {

 		return "", "", err

@@ -681,12 +680,12 @@ func (p *v2Puller) pullManifestList(ctx context.Context, ref reference.Named, mf

 	switch v := manifest.(type) {

 	case *schema1.SignedManifest:

-		imageID, _, err = p.pullSchema1(ctx, manifestRef, v)

+		id, _, err = p.pullSchema1(ctx, manifestRef, v)

 		if err != nil {

 			return "", "", err

 		}

 	case *schema2.DeserializedManifest:

-		imageID, _, err = p.pullSchema2(ctx, manifestRef, v)

+		id, _, err = p.pullSchema2(ctx, manifestRef, v)

 		if err != nil {

 			return "", "", err

 		}

@@ -694,10 +693,10 @@ func (p *v2Puller) pullManifestList(ctx context.Context, ref reference.Named, mf

 		return "", "", errors.New("unsupported manifest format")

 	}

-	return imageID, manifestListDigest, err

+	return id, manifestListDigest, err

 }

-func (p *v2Puller) pullSchema2ImageConfig(ctx context.Context, dgst digest.Digest) (configJSON []byte, err error) {

+func (p *v2Puller) pullSchema2Config(ctx context.Context, dgst digest.Digest) (configJSON []byte, err error) {

 	blobs := p.repo.Blobs(ctx)

 	configJSON, err = blobs.Get(ctx, dgst)

 	if err != nil {

@@ -92,7 +92,7 @@ type v1TopImage struct {

 }

 func newV1TopImage(imageID image.ID, img *image.Image, l layer.Layer, parent *v1DependencyImage) (*v1TopImage, error) {

-	v1ID := digest.Digest(imageID).Hex()

+	v1ID := imageID.Digest().Hex()

 	parentV1ID := ""

 	if parent != nil {

 		parentV1ID = parent.V1ID()

@@ -149,10 +149,12 @@ func (p *v1Pusher) getImageList() (imageList []v1Image, tagsByImage map[image.ID

 	if isTagged {

 		// Push a specific tag

 		var imgID image.ID

-		imgID, err = p.config.ReferenceStore.Get(p.ref)

+		var dgst digest.Digest

+		dgst, err = p.config.ReferenceStore.Get(p.ref)

 		if err != nil {

 			return

 		}

+		imgID = image.IDFromDigest(dgst)

 		imageList, err = p.imageListForTag(imgID, nil, &referencedLayers)

 		if err != nil {

@@ -164,7 +166,7 @@ func (p *v1Pusher) getImageList() (imageList []v1Image, tagsByImage map[image.ID

 		return

 	}

-	imagesSeen := make(map[image.ID]struct{})

+	imagesSeen := make(map[digest.Digest]struct{})

 	dependenciesSeen := make(map[layer.ChainID]*v1DependencyImage)

 	associations := p.config.ReferenceStore.ReferencesByName(p.ref)

@@ -174,15 +176,16 @@ func (p *v1Pusher) getImageList() (imageList []v1Image, tagsByImage map[image.ID

 			continue

 		}

-		tagsByImage[association.ImageID] = append(tagsByImage[association.ImageID], tagged.Tag())

+		imgID := image.IDFromDigest(association.ID)

+		tagsByImage[imgID] = append(tagsByImage[imgID], tagged.Tag())

-		if _, present := imagesSeen[association.ImageID]; present {

+		if _, present := imagesSeen[association.ID]; present {

 			// Skip generating image list for already-seen image

 			continue

 		}

-		imagesSeen[association.ImageID] = struct{}{}

+		imagesSeen[association.ID] = struct{}{}

-		imageListForThisTag, err := p.imageListForTag(association.ImageID, dependenciesSeen, &referencedLayers)

+		imageListForThisTag, err := p.imageListForTag(imgID, dependenciesSeen, &referencedLayers)

 		if err != nil {

 			return nil, nil, nil, err

 		}

@@ -99,7 +99,7 @@ func (p *v2Pusher) pushV2Repository(ctx context.Context) (err error) {

 	for _, association := range p.config.ReferenceStore.ReferencesByName(p.ref) {

 		if namedTagged, isNamedTagged := association.Ref.(reference.NamedTagged); isNamedTagged {

 			pushed++

-			if err := p.pushV2Tag(ctx, namedTagged, association.ImageID); err != nil {

+			if err := p.pushV2Tag(ctx, namedTagged, association.ID); err != nil {

 				return err

 			}

 		}

@@ -112,10 +112,10 @@ func (p *v2Pusher) pushV2Repository(ctx context.Context) (err error) {

 	return nil

 }

-func (p *v2Pusher) pushV2Tag(ctx context.Context, ref reference.NamedTagged, imageID image.ID) error {

+func (p *v2Pusher) pushV2Tag(ctx context.Context, ref reference.NamedTagged, id digest.Digest) error {

 	logrus.Debugf("Pushing repository: %s", ref.String())

-	img, err := p.config.ImageStore.Get(imageID)

+	img, err := p.config.ImageStore.Get(image.IDFromDigest(id))

 	if err != nil {

 		return fmt.Errorf("could not find image from tag %s: %v", ref.String(), err)

 	}

@@ -207,7 +207,7 @@ func (p *v2Pusher) pushV2Tag(ctx context.Context, ref reference.NamedTagged, ima

 	manifestDigest := digest.FromBytes(canonicalManifest)

 	progress.Messagef(p.config.ProgressOutput, "", "%s: digest: %s size: %d", ref.Tag(), manifestDigest, len(canonicalManifest))

-	if err := addDigestReference(p.config.ReferenceStore, ref, manifestDigest, imageID); err != nil {

+	if err := addDigestReference(p.config.ReferenceStore, ref, manifestDigest, id); err != nil {

 		return err

 	}

@@ -12,18 +12,18 @@ import (

 	"github.com/docker/docker/pkg/ioutils"

 )

-// IDWalkFunc is function called by StoreBackend.Walk

-type IDWalkFunc func(id ID) error

+// DigestWalkFunc is function called by StoreBackend.Walk

+type DigestWalkFunc func(id digest.Digest) error

 // StoreBackend provides interface for image.Store persistence

 type StoreBackend interface {

-	Walk(f IDWalkFunc) error

-	Get(id ID) ([]byte, error)

-	Set(data []byte) (ID, error)

-	Delete(id ID) error

-	SetMetadata(id ID, key string, data []byte) error

-	GetMetadata(id ID, key string) ([]byte, error)

-	DeleteMetadata(id ID, key string) error

+	Walk(f DigestWalkFunc) error

+	Get(id digest.Digest) ([]byte, error)

+	Set(data []byte) (digest.Digest, error)

+	Delete(id digest.Digest) error

+	SetMetadata(id digest.Digest, key string, data []byte) error

+	GetMetadata(id digest.Digest, key string) ([]byte, error)

+	DeleteMetadata(id digest.Digest, key string) error

 }

 // fs implements StoreBackend using the filesystem.

@@ -55,18 +55,16 @@ func newFSStore(root string) (*fs, error) {

 	return s, nil

 }

-func (s *fs) contentFile(id ID) string {

-	dgst := digest.Digest(id)

+func (s *fs) contentFile(dgst digest.Digest) string {

 	return filepath.Join(s.root, contentDirName, string(dgst.Algorithm()), dgst.Hex())

 }

-func (s *fs) metadataDir(id ID) string {

-	dgst := digest.Digest(id)

+func (s *fs) metadataDir(dgst digest.Digest) string {

 	return filepath.Join(s.root, metadataDirName, string(dgst.Algorithm()), dgst.Hex())

 }

 // Walk calls the supplied callback for each image ID in the storage backend.

-func (s *fs) Walk(f IDWalkFunc) error {

+func (s *fs) Walk(f DigestWalkFunc) error {

 	// Only Canonical digest (sha256) is currently supported

 	s.RLock()

 	dir, err := ioutil.ReadDir(filepath.Join(s.root, contentDirName, string(digest.Canonical)))

@@ -80,37 +78,37 @@ func (s *fs) Walk(f IDWalkFunc) error {

 			logrus.Debugf("Skipping invalid digest %s: %s", dgst, err)

 			continue

 		}

-		if err := f(ID(dgst)); err != nil {

+		if err := f(dgst); err != nil {

 			return err

 		}

 	}

 	return nil

 }

-// Get returns the content stored under a given ID.

-func (s *fs) Get(id ID) ([]byte, error) {

+// Get returns the content stored under a given digest.

+func (s *fs) Get(dgst digest.Digest) ([]byte, error) {

 	s.RLock()

 	defer s.RUnlock()

-	return s.get(id)

+	return s.get(dgst)

 }

-func (s *fs) get(id ID) ([]byte, error) {

-	content, err := ioutil.ReadFile(s.contentFile(id))

+func (s *fs) get(dgst digest.Digest) ([]byte, error) {

+	content, err := ioutil.ReadFile(s.contentFile(dgst))

 	if err != nil {

 		return nil, err

 	}

 	// todo: maybe optional

-	if ID(digest.FromBytes(content)) != id {

-		return nil, fmt.Errorf("failed to verify image: %v", id)

+	if digest.FromBytes(content) != dgst {

+		return nil, fmt.Errorf("failed to verify: %v", dgst)

 	}

 	return content, nil

 }

-// Set stores content under a given ID.

-func (s *fs) Set(data []byte) (ID, error) {

+// Set stores content by checksum.

+func (s *fs) Set(data []byte) (digest.Digest, error) {

 	s.Lock()

 	defer s.Unlock()

@@ -118,58 +116,58 @@ func (s *fs) Set(data []byte) (ID, error) {

 		return "", fmt.Errorf("Invalid empty data")

 	}

-	id := ID(digest.FromBytes(data))

-	if err := ioutils.AtomicWriteFile(s.contentFile(id), data, 0600); err != nil {

+	dgst := digest.FromBytes(data)

+	if err := ioutils.AtomicWriteFile(s.contentFile(dgst), data, 0600); err != nil {

 		return "", err

 	}

-	return id, nil

+	return dgst, nil

 }

-// Delete removes content and metadata files associated with the ID.

-func (s *fs) Delete(id ID) error {

+// Delete removes content and metadata files associated with the digest.

+func (s *fs) Delete(dgst digest.Digest) error {

 	s.Lock()

 	defer s.Unlock()

-	if err := os.RemoveAll(s.metadataDir(id)); err != nil {

+	if err := os.RemoveAll(s.metadataDir(dgst)); err != nil {

 		return err

 	}

-	if err := os.Remove(s.contentFile(id)); err != nil {

+	if err := os.Remove(s.contentFile(dgst)); err != nil {

 		return err

 	}

 	return nil

 }

 // SetMetadata sets metadata for a given ID. It fails if there's no base file.

-func (s *fs) SetMetadata(id ID, key string, data []byte) error {

+func (s *fs) SetMetadata(dgst digest.Digest, key string, data []byte) error {

 	s.Lock()

 	defer s.Unlock()

-	if _, err := s.get(id); err != nil {

+	if _, err := s.get(dgst); err != nil {

 		return err

 	}

-	baseDir := filepath.Join(s.metadataDir(id))

+	baseDir := filepath.Join(s.metadataDir(dgst))

 	if err := os.MkdirAll(baseDir, 0700); err != nil {

 		return err

 	}

-	return ioutils.AtomicWriteFile(filepath.Join(s.metadataDir(id), key), data, 0600)

+	return ioutils.AtomicWriteFile(filepath.Join(s.metadataDir(dgst), key), data, 0600)

 }

-// GetMetadata returns metadata for a given ID.

-func (s *fs) GetMetadata(id ID, key string) ([]byte, error) {

+// GetMetadata returns metadata for a given digest.

+func (s *fs) GetMetadata(dgst digest.Digest, key string) ([]byte, error) {

 	s.RLock()

 	defer s.RUnlock()

-	if _, err := s.get(id); err != nil {

+	if _, err := s.get(dgst); err != nil {

 		return nil, err

 	}

-	return ioutil.ReadFile(filepath.Join(s.metadataDir(id), key))

+	return ioutil.ReadFile(filepath.Join(s.metadataDir(dgst), key))

 }

-// DeleteMetadata removes the metadata associated with an ID.

-func (s *fs) DeleteMetadata(id ID, key string) error {

+// DeleteMetadata removes the metadata associated with a digest.

+func (s *fs) DeleteMetadata(dgst digest.Digest, key string) error {

 	s.Lock()

 	defer s.Unlock()

-	return os.RemoveAll(filepath.Join(s.metadataDir(id), key))

+	return os.RemoveAll(filepath.Join(s.metadataDir(dgst), key))

 }

@@ -128,7 +128,7 @@ func testMetadataGetSet(t *testing.T, store StoreBackend) {

 	}

 	tcases := []struct {

-		id    ID

+		id    digest.Digest

 		key   string

 		value []byte

 	}{

@@ -158,12 +158,12 @@ func testMetadataGetSet(t *testing.T, store StoreBackend) {

 	}

 	id3 := digest.FromBytes([]byte("baz"))

-	err = store.SetMetadata(ID(id3), "tkey", []byte("tval"))

+	err = store.SetMetadata(id3, "tkey", []byte("tval"))

 	if err == nil {

 		t.Fatal("Expected error for setting metadata for unknown ID.")

 	}

-	_, err = store.GetMetadata(ID(id3), "tkey")

+	_, err = store.GetMetadata(id3, "tkey")

 	if err == nil {

 		t.Fatal("Expected error for getting metadata for unknown ID.")

 	}

@@ -232,7 +232,7 @@ func TestFSInvalidWalker(t *testing.T) {

 	}

 	n := 0

-	err = fs.Walk(func(id ID) error {

+	err = fs.Walk(func(id digest.Digest) error {

 		if id != fooID {

 			t.Fatalf("Invalid walker ID %q, expected %q", id, fooID)

 		}

@@ -250,10 +250,10 @@ func TestFSInvalidWalker(t *testing.T) {

 func testGetSet(t *testing.T, store StoreBackend) {

 	type tcase struct {

 		input    []byte

-		expected ID

+		expected digest.Digest

 	}

 	tcases := []tcase{

-		{[]byte("foobar"), ID("sha256:c3ab8ff13720e8ad9047dd39466b3c8974e592c2fa383d4a3960714caef0c4f2")},

+		{[]byte("foobar"), digest.Digest("sha256:c3ab8ff13720e8ad9047dd39466b3c8974e592c2fa383d4a3960714caef0c4f2")},

 	}

 	randomInput := make([]byte, 8*1024)

@@ -269,7 +269,7 @@ func testGetSet(t *testing.T, store StoreBackend) {

 	}

 	tcases = append(tcases, tcase{

 		input:    randomInput,

-		expected: ID("sha256:" + hex.EncodeToString(h.Sum(nil))),

+		expected: digest.Digest("sha256:" + hex.EncodeToString(h.Sum(nil))),

 	})

 	for _, tc := range tcases {

@@ -299,7 +299,7 @@ func testGetSet(t *testing.T, store StoreBackend) {

 		}

 	}

-	for _, key := range []ID{"foobar:abc", "sha256:abc", "sha256:c3ab8ff13720e8ad9047dd39466b3c8974e592c2fa383d4a3960714caef0c4f2a"} {

+	for _, key := range []digest.Digest{"foobar:abc", "sha256:abc", "sha256:c3ab8ff13720e8ad9047dd39466b3c8974e592c2fa383d4a3960714caef0c4f2a"} {

 		_, err := store.Get(key)

 		if err == nil {

 			t.Fatalf("Expected error for ID %q.", key)

@@ -352,11 +352,11 @@ func testWalker(t *testing.T, store StoreBackend) {

 		t.Fatal(err)

 	}

-	tcases := make(map[ID]struct{})

+	tcases := make(map[digest.Digest]struct{})

 	tcases[id] = struct{}{}

 	tcases[id2] = struct{}{}

 	n := 0

-	err = store.Walk(func(id ID) error {

+	err = store.Walk(func(id digest.Digest) error {

 		delete(tcases, id)

 		n++

 		return nil

@@ -373,9 +373,9 @@ func testWalker(t *testing.T, store StoreBackend) {

 	}

 	// stop on error

-	tcases = make(map[ID]struct{})

+	tcases = make(map[digest.Digest]struct{})

 	tcases[id] = struct{}{}

-	err = store.Walk(func(id ID) error {

+	err = store.Walk(func(id digest.Digest) error {

 		return errors.New("")

 	})

 	if err == nil {

@@ -14,7 +14,17 @@ import (

 type ID digest.Digest

 func (id ID) String() string {

-	return digest.Digest(id).String()

+	return id.Digest().String()

+}

+

+// Digest converts ID into a digest

+func (id ID) Digest() digest.Digest {

+	return digest.Digest(id)

+}

+

+// IDFromDigest creates an ID from a digest

+func IDFromDigest(digest digest.Digest) ID {

+	return ID(digest)

 }

 // V1Image stores the V1 image configuration.

@@ -72,9 +82,9 @@ func (img *Image) ID() ID {

 	return img.computedID

 }

-// ImageID stringizes ID.

+// ImageID stringifies ID.

 func (img *Image) ImageID() string {

-	return string(img.ID())

+	return img.ID().String()

 }

 // RunConfig returns the image's container config.

@@ -61,10 +61,10 @@ func NewImageStore(fs StoreBackend, ls LayerGetReleaser) (Store, error) {

 }

 func (is *store) restore() error {

-	err := is.fs.Walk(func(id ID) error {

-		img, err := is.Get(id)

+	err := is.fs.Walk(func(dgst digest.Digest) error {

+		img, err := is.Get(IDFromDigest(dgst))

 		if err != nil {

-			logrus.Errorf("invalid image %v, %v", id, err)

+			logrus.Errorf("invalid image %v, %v", dgst, err)

 			return nil

 		}

 		var l layer.Layer

@@ -74,7 +74,7 @@ func (is *store) restore() error {

 				return err

 			}

 		}

-		if err := is.digestSet.Add(digest.Digest(id)); err != nil {

+		if err := is.digestSet.Add(dgst); err != nil {

 			return err

 		}

@@ -83,7 +83,7 @@ func (is *store) restore() error {

 			children: make(map[ID]struct{}),

 		}

-		is.images[ID(id)] = imageMeta

+		is.images[IDFromDigest(dgst)] = imageMeta

 		return nil

 	})

@@ -131,7 +131,7 @@ func (is *store) Create(config []byte) (ID, error) {

 	if err != nil {

 		return "", err

 	}

-	imageID := ID(dgst)

+	imageID := IDFromDigest(dgst)

 	is.Lock()

 	defer is.Unlock()

@@ -156,7 +156,7 @@ func (is *store) Create(config []byte) (ID, error) {

 	}

 	is.images[imageID] = imageMeta

-	if err := is.digestSet.Add(digest.Digest(imageID)); err != nil {

+	if err := is.digestSet.Add(imageID.Digest()); err != nil {

 		delete(is.images, imageID)

 		return "", err

 	}

@@ -175,13 +175,13 @@ func (is *store) Search(term string) (ID, error) {

 		}

 		return "", err

 	}

-	return ID(dgst), nil

+	return IDFromDigest(dgst), nil

 }

 func (is *store) Get(id ID) (*Image, error) {

 	// todo: Check if image is in images

 	// todo: Detect manual insertions and start using them

-	config, err := is.fs.Get(id)

+	config, err := is.fs.Get(id.Digest())

 	if err != nil {

 		return nil, err

 	}

@@ -209,17 +209,17 @@ func (is *store) Delete(id ID) ([]layer.Metadata, error) {

 		return nil, fmt.Errorf("unrecognized image ID %s", id.String())

 	}

 	for id := range imageMeta.children {

-		is.fs.DeleteMetadata(id, "parent")

+		is.fs.DeleteMetadata(id.Digest(), "parent")

 	}

 	if parent, err := is.GetParent(id); err == nil && is.images[parent] != nil {

 		delete(is.images[parent].children, id)

 	}

-	if err := is.digestSet.Remove(digest.Digest(id)); err != nil {

+	if err := is.digestSet.Remove(id.Digest()); err != nil {

 		logrus.Errorf("error removing %s from digest set: %q", id, err)

 	}

 	delete(is.images, id)

-	is.fs.Delete(id)

+	is.fs.Delete(id.Digest())

 	if imageMeta.layer != nil {

 		return is.ls.Release(imageMeta.layer)

@@ -238,11 +238,11 @@ func (is *store) SetParent(id, parent ID) error {

 		delete(is.images[parent].children, id)

 	}

 	parentMeta.children[id] = struct{}{}

-	return is.fs.SetMetadata(id, "parent", []byte(parent))

+	return is.fs.SetMetadata(id.Digest(), "parent", []byte(parent))

 }

 func (is *store) GetParent(id ID) (ID, error) {

-	d, err := is.fs.GetMetadata(id, "parent")

+	d, err := is.fs.GetMetadata(id.Digest(), "parent")

 	if err != nil {

 		return "", err

 	}

@@ -11,6 +11,7 @@ import (

 	"github.com/Sirupsen/logrus"

 	"github.com/docker/distribution"

+	"github.com/docker/distribution/digest"

 	"github.com/docker/docker/image"

 	"github.com/docker/docker/image/v1"

 	"github.com/docker/docker/layer"

@@ -123,7 +124,7 @@ func (l *tarexporter) Load(inTar io.ReadCloser, outStream io.Writer, quiet bool)

 			if !ok {

 				return fmt.Errorf("invalid tag %q", repoTag)

 			}

-			l.setLoadedTag(ref, imgID, outStream)

+			l.setLoadedTag(ref, imgID.Digest(), outStream)

 			outStream.Write([]byte(fmt.Sprintf("Loaded image: %s\n", ref)))

 			imageRefCount++

 		}

@@ -195,7 +196,7 @@ func (l *tarexporter) loadLayer(filename string, rootFS image.RootFS, id string,

 	return l.ls.Register(inflatedLayerData, rootFS.ChainID())

 }

-func (l *tarexporter) setLoadedTag(ref reference.NamedTagged, imgID image.ID, outStream io.Writer) error {

+func (l *tarexporter) setLoadedTag(ref reference.NamedTagged, imgID digest.Digest, outStream io.Writer) error {

 	if prevID, err := l.rs.Get(ref); err == nil && prevID != imgID {

 		fmt.Fprintf(outStream, "The image %s already exists, renaming the old one with ID %s to empty string\n", ref.String(), string(prevID)) // todo: this message is wrong in case of multiple tags

 	}

@@ -253,7 +254,7 @@ func (l *tarexporter) legacyLoad(tmpDir string, outStream io.Writer, progressOut

 			if err != nil {

 				return err

 			}

-			l.setLoadedTag(ref, imgID, outStream)

+			l.setLoadedTag(ref, imgID.Digest(), outStream)

 		}

 	}

@@ -77,11 +77,11 @@ func (l *tarexporter) parseNames(names []string) (map[image.ID]*imageDescriptor,

 			return nil, err

 		}

 		if id != "" {

-			_, err := l.is.Get(image.ID(id))

+			_, err := l.is.Get(image.IDFromDigest(id))

 			if err != nil {

 				return nil, err

 			}

-			addAssoc(image.ID(id), nil)

+			addAssoc(image.IDFromDigest(id), nil)

 			continue

 		}

 		if ref.Name() == string(digest.Canonical) {

@@ -95,7 +95,7 @@ func (l *tarexporter) parseNames(names []string) (map[image.ID]*imageDescriptor,

 		if reference.IsNameOnly(ref) {

 			assocs := l.rs.ReferencesByName(ref)

 			for _, assoc := range assocs {

-				addAssoc(assoc.ImageID, assoc.Ref)

+				addAssoc(image.IDFromDigest(assoc.ID), assoc.Ref)

 			}

 			if len(assocs) == 0 {

 				imgID, err := l.is.Search(name)

@@ -106,11 +106,11 @@ func (l *tarexporter) parseNames(names []string) (map[image.ID]*imageDescriptor,

 			}

 			continue

 		}

-		var imgID image.ID

-		if imgID, err = l.rs.Get(ref); err != nil {

+		id, err = l.rs.Get(ref)

+		if err != nil {

 			return nil, err

 		}

-		addAssoc(imgID, ref)

+		addAssoc(image.IDFromDigest(id), ref)

 	}

 	return imgDescr, nil

@@ -155,7 +155,7 @@ func (s *saveSession) save(outStream io.Writer) error {

 		}

 		manifest = append(manifest, manifestItem{

-			Config:       digest.Digest(id).Hex() + ".json",

+			Config:       id.Digest().Hex() + ".json",

 			RepoTags:     repoTags,

 			Layers:       layers,

 			LayerSources: foreignSrcs,

@@ -264,7 +264,7 @@ func (s *saveSession) saveImage(id image.ID) (map[layer.DiffID]distribution.Desc

 		}

 	}

-	configFile := filepath.Join(s.outDir, digest.Digest(id).Hex()+".json")

+	configFile := filepath.Join(s.outDir, id.Digest().Hex()+".json")

 	if err := ioutil.WriteFile(configFile, img.RawJSON(), 0644); err != nil {

 		return nil, err

 	}

@@ -294,8 +294,8 @@ func migrateContainers(root string, ls graphIDMounter, is image.Store, imageMapp

 }