Ciphertext decryption doubts

What prevents a malicious user from deploying a contract to decrypt ciphertexts published on the blockchain? If the only input for transactions carried out by Remix is the ciphertexts (generated using the Command-Line Interface (CLI) tool), how do we know that the sender itself generated the ciphertext? Furthermore, if the owner of the ciphertext wants to decrypt his ciphertext published on the blockchain intentionally through a function in a smart contract, can he?

If you want to pass a ciphertext as input in a function, you need to provide a zero-knowledge proof. So you can’t copy a ciphertext and send it as it is.
This proof system is not implemented yet, but will be soon :slight_smile: