Decrypt a LockBox encrypted and signed using public key cryptography.
The message is decrypted using the private key of the recipient (sk) and
the signature is verified using the public key of the sender (pk).
If decryption or verification fails, null is returned.
Decrypt a LockBox encrypted and signed using public key cryptography. The message is decrypted using the private key of the recipient (sk) and the signature is verified using the public key of the sender (pk). If decryption or verification fails, null is returned.