Ciphertext is encrypted text that requires a decryption keyA decryption key is a string of characters used to decrypt ciphertext and restore the cipher back to its original... Read More to read. Converting ciphertext into readable plaintextPlaintext is the data that a computer system processes without encryption. Plaintext typically takes the form of characters, numbers, or... Read More requires the appropriate key and decryption algorithmA decryption algorithm is an algorithm used to decrypt encrypted data. In other words, it is a mathematical process to... Read More. Without these two things, ciphertext is unreadable and effectively useless.