}

	keyID, b64Key := v[0], v[1]
	key, err := base64.StdEncoding.DecodeString(b64Key)
	if err != nil {
		return nil, err
	}
	return NewBuiltin(keyID, key)
}

// NewBuiltin returns a single-key KMS that derives new DEKs from the
// given key.
func NewBuiltin(keyID string, key []byte) (*KMS, error) {
	if len(key) != 32 {
		return nil, errors.New("kms: invalid key length " + strconv.Itoa(len(key)))
	}
	return &KMS{