Cyphertext

To this goal Alice encrypts the plaintext into a cyphertext by mean of an encryption algorithm with the help of some secret additional information, called key.

The cyphertext can be randomized by everyone, but the entity that performs the re-encryption can identify if the cyphertext is safe.

In simple terms, encryption is the process of converting plaintext, such as messages or information, into a data format that is unreadable by human or computer, known as cyphertext, using an encryption algorithm.