Of the two processes used in symmetric key cryptography, which involves XORing the plaintext message with the key?

In symmetric key cryptography, the process that involves XORing the plaintext message with the key is known as encryption. The XOR operation is a fundamental method used to create ciphertext from plaintext when combined with a secret key. This operation works by comparing each bit of the plaintext with the corresponding bit of the key; if the bits are the same, the resulting bit is 0, and if they are different, the resulting bit is 1.

This method is effective because it creates a simple yet secure way of transforming data. When the same key is used for both encryption and decryption, understanding this relationship is crucial. By XORing the ciphertext (result of the initial XOR operation) with the same key, you can retrieve the original plaintext.

While substitution and transposition are also methods used in cryptographic algorithms, they do not specifically refer to the process of XORing the plaintext with the key. Substitution involves replacing elements of the plaintext with other elements according to a defined system, while transposition focuses on rearranging the order of the bits or characters in the data without changing their values.