The process wherein the ciphertext block is encrypted then the ciphertext produced is XOR'd back with the plaintext to produce the current ciphertext block is called what?

The process described involves taking a block of ciphertext, encrypting it, and then XORing this encrypted output back with the original plaintext to create the next ciphertext block. This method is characteristic of Cipher Feedback (CFB) mode.

In CFB mode, the mechanism works by treating the encryption algorithm as a key-stream generator. The previous ciphertext block is encrypted and then combined with the plaintext through the XOR operation to create the current ciphertext. This enables the encryption of smaller block sizes than the original cipher, allowing for variable-length inputs without needing to pad.

CFB is particularly advantageous in scenarios where error propagation needs to be limited, as a single bit error in the ciphertext will only affect the corresponding decrypted plaintext bit and the following bits during decryption. This property allows for a more resilient mode of operation, making it suitable for applications where data integrity is critical.

Other modes mentioned, such as Output Feedback (OFB), Counter Mode (CTR), and Electronic Codebook (ECB), function differently, focusing on generating cipher streams or operating on blocks without chaining the previous ciphertext to the current plaintext. Thus, the specific operations described align clearly with the principles of Cipher Feedback mode.