mandatory decryption is technically a weaker requirement than key disclosure, since it is possible in some cryptosystems to prove that a message has been decrypted correctly without revealing the key. for example, using rsa public-key encryption, one can verify given the message (plaintext), the encrypted message (ciphertext), and the public key of the recipient that the message is correct by merely re-encrypting it and comparing the result to the encrypted message. such a scheme is called "undeniable", since once the government has validated the message they cannot deny that it is the correct decrypted message.