func (ssekms) ParseMetadata(metadata map[string]string) (keyID string, kmsKey []byte, sealedKey SealedKey, ctx kms.Context, err error) {
	// Extract all required values from object metadata
	b64IV, ok := metadata[MetaIV]
	if !ok {
		return keyID, kmsKey, sealedKey, ctx, errMissingInternalIV
	}
	algorithm, ok := metadata[MetaAlgorithm]
	if !ok {
		return keyID, kmsKey, sealedKey, ctx, errMissingInternalSealAlgorithm
	}