diff --git a/registry/client/transport/http_reader.go b/registry/client/transport/http_reader.go
index d10d37e06..e351bdfe3 100644
--- a/registry/client/transport/http_reader.go
+++ b/registry/client/transport/http_reader.go
@@ -9,14 +9,19 @@ import (
 	"io/ioutil"
 	"net/http"
 	"os"
-
-	"github.com/docker/distribution"
 )
 
+// ReadSeekCloser combines io.ReadSeeker with io.Closer.
+type ReadSeekCloser interface {
+	io.ReadSeeker
+	io.Closer
+}
+
 // NewHTTPReadSeeker handles reading from an HTTP endpoint using a GET
 // request. When seeking and starting a read from a non-zero offset
 // the a "Range" header will be added which sets the offset.
-func NewHTTPReadSeeker(client *http.Client, url string, size int64) distribution.ReadSeekCloser {
+// TODO(dmcgowan): Move this into a separate utility package
+func NewHTTPReadSeeker(client *http.Client, url string, size int64) ReadSeekCloser {
 	return &httpReadSeeker{
 		client: client,
 		url:    url,
diff --git a/registry/client/transport/session.go b/registry/client/transport/session.go
index 670be1ba8..5086c0211 100644
--- a/registry/client/transport/session.go
+++ b/registry/client/transport/session.go
@@ -14,7 +14,12 @@ import (
 // AuthenticationHandler is an interface for authorizing a request from
 // params from a "WWW-Authenicate" header for a single scheme.
 type AuthenticationHandler interface {
+	// Scheme returns the scheme as expected from the "WWW-Authenicate" header.
 	Scheme() string
+
+	// AuthorizeRequest adds the authorization header to a request (if needed)
+	// using the parameters from "WWW-Authenticate" method. The parameters
+	// values depend on the scheme.
 	AuthorizeRequest(req *http.Request, params map[string]string) error
 }