GnnForPrivacyScan/data/purposeSplit/Hash/crypto_7.py

def decrypt(self, key, ciphertext, verify=False):
    """ decrypt data with convergence encryption.
    
        Args
            key: str, encryption key
            cipher: str, ciphertext
            verify: bool, verify decrypted data, default: False
    
        Returns
            the plain text
    """
    plain = aes(key, ciphertext)
    if verify:
        h = SHA256d(plain)
        if self.__convergence_secret:
            h.update(self.__convergence_secret)
        digest = h.digest()
        # can verify only if convergence secret is known!
        if self.__convergence_secret and not key == digest:
            msg = "Block verification error on %s." % SHA256d(key).hexdigest()
            log.error(msg)
            raise CryptError(msg)
    return plain