prf := hmac.New(sha256.New, s.key)
	prf.Write(iv)
	key := prf.Sum(make([]byte, 0, prf.Size()))

	block, err := aes.NewCipher(key)
	if err != nil {
		return DEK{}, err
	}
	aead, err := cipher.NewGCM(block)
	if err != nil {
		return DEK{}, err
	}

	plaintext, err := sioutil.Random(32)
	if err != nil {
		return DEK{}, err
	}
	ciphertext := aead.Seal(nil, nonce, plaintext, associatedData)