code: func DecryptSymmetric(ciphertext []byte, secret []byte) (plaintext []byte, err error) {
  	if len(secret) != secretLen {
  		PanicSanity(Fmt("Secret must be 32 bytes long, got len %v", len(secret)))
  	}
  	if len(ciphertext) <= secretbox.Overhead+nonceLen {
  		return nil, errors.New("Ciphertext is too short")
  	}
  	nonce := ciphertext[:nonceLen]
  	nonceArr := [nonceLen]byte{}
  	copy(nonceArr[:], nonce)
  	secretArr := [secretLen]byte{}
  	copy(secretArr[:], secret)
  	plaintext = make([]byte, len(ciphertext)-nonceLen-secretbox.Overhead)
  	_, ok := secretbox.Open(plaintext[:0], ciphertext[nonceLen:], &nonceArr, &secretArr)
  	if !ok {
  		return nil, errors.New("Ciphertext decryption failed")
  	}
  	return plaintext, nil
  }
docs: // secret must be 32 bytes long. Use something like Sha256(Bcrypt(passphrase))
  // The ciphertext is (secretbox.Overhead + 24) bytes longer than the plaintext.