code: def symmetric_decrypt_HMAC(cyphertext, key, hmac_secret):
      
      iv = symmetric_decrypt_iv(cyphertext, key)
      message = symmetric_decrypt_with_iv(cyphertext, key, iv)
  
      hmac = hmac_sha1(hmac_secret, iv[-3:] + message)
  
      if iv[:13] != hmac[:13]:
          raise RuntimeError("Unable to decrypt message. HMAC does not match.")
  
      return message
docs: :raises: :class:`RuntimeError` when HMAC verification fails