Simplify and rename hash functions

pkg/tuf/registry_test.go

@@ -121,7 +121,7 @@ func TestFindFileInManifest(t *testing.T) {
 	// make test image manifest
 	file := "test.json"
 	data := []byte("test")
-	hash := v1.Hash{Algorithm: "sha256", Hex: util.HexHashBytes(data)}
+	hash := v1.Hash{Algorithm: "sha256", Hex: util.SHA256Hex(data)}
 	img := empty.Image
 	img = mutate.MediaType(img, types.OCIManifestSchema1)
 	img = mutate.ConfigMediaType(img, types.OCIConfigJSON)

pkg/tuf/tuf.go

@@ -44,7 +44,7 @@ func NewTufClient(initialRoot []byte, tufPath, metadataSource, targetsSource str
 		tufSource = OciSource
 	}
 
-	tufRootDigest := util.HexHashBytes(initialRoot)
+	tufRootDigest := util.SHA256Hex(initialRoot)
 
 	// create a directory for each initial root.json
 	metadataPath := filepath.Join(tufPath, tufRootDigest)