if err != nil {
			return keyID, kmsKey, sealedKey, Errorf("The internal sealed KMS data key for SSE-S3 is invalid")
		}
	}

	sealedKey.Algorithm = algorithm
	copy(sealedKey.IV[:], iv)
	copy(sealedKey.Key[:], encryptedKey)
	return keyID, kmsKey, sealedKey, nil

// metadata map if metadata is nil.
func (ssec) CreateMetadata(metadata map[string]string, sealedKey SealedKey) map[string]string {
	if sealedKey.Algorithm != SealAlgorithm {
		logger.CriticalIf(context.Background(), Errorf("The seal algorithm '%s' is invalid for SSE-C", sealedKey.Algorithm))
	}

	if metadata == nil {
		metadata = make(map[string]string, 3)
	}

//     -       SealedKey := DAREv2_Enc(KeyEncKey, ObjectKey)
//     - enc_object_data := DAREv2_Enc(ObjectKey, object_data)
//     -        metadata <- IV
//     -        metadata <- SealedKey
//     Output: enc_object_data, metadata
//
//  2. Decrypt:
//     Input: ClientKey, bucket, object, metadata, enc_object_data
//     -          IV <- metadata
//     -   SealedKey <- metadata

		if err = json.Unmarshal(b, &ctx); err != nil {
			return keyID, kmsKey, sealedKey, ctx, Errorf("The internal sealed KMS context is invalid %w", err)
		}
	}

	sealedKey.Algorithm = algorithm
	copy(sealedKey.IV[:], iv)
	copy(sealedKey.Key[:], encryptedKey)
	return keyID, kmsKey, sealedKey, ctx, nil

	var extKey, iv [32]byte
	key := GenerateKey(extKey[:], rand.Reader)
	sealedKey := key.Seal(extKey[:], iv, "SSE-S3", "bucket", "object")
	sealedKey.Algorithm = InsecureSealAlgorithm
	if err := key.Unseal(extKey[:], sealedKey, "SSE-S3", "bucket", "object"); err == nil {
		t.Errorf("'%s' test succeeded but it should fail because the legacy algorithm was used", sealedKey.Algorithm)
	}
}

var derivePartKeyTest = []struct {

func (key *ObjectKey) Unseal(extKey []byte, sealedKey SealedKey, domain, bucket, object string) error {
	var unsealConfig sio.Config
	switch sealedKey.Algorithm {
	default:
		return Errorf("The sealing algorithm '%s' is not supported", sealedKey.Algorithm)
	case SealAlgorithm:
		mac := hmac.New(sha256.New, extKey)
		mac.Write(sealedKey.IV[:])
		mac.Write([]byte(domain))
		mac.Write([]byte(SealAlgorithm))

// from the metadata using the SSE-C client key.
func unsealObjectKey(clientKey []byte, metadata map[string]string, bucket, object string) (key ObjectKey, err error) {
	sealedKey, err := SSEC.ParseMetadata(metadata)
	if err != nil {
		return
	}
	err = key.Unseal(clientKey, sealedKey, SSEC.String(), bucket, object)
	return
}

// EncryptSinglePart encrypts an io.Reader which must be the
// body of a single-part PUT request.