Crypto U4, Block Cipher, Counter Mode

Encryption Both sender and receiver have an agreed upon counter starting number. Pass the first counter number and the key to the encryption function. XOR the result of the function with the first plaintext block. The result is the first ciphertext block. Increment the counter. Pass the new counter value and the key to the encryption function. XOR the result of the function with the next plaintext block. The result is the next ciphertext block. Go to step number 5 and repeat until there are no plaintext blocks remaining.

Decryption Take the agreed upon counter number. Pass the starting counter number and the key to the encryption function. XOR the result of the function with the first ciphertext block. The result is the first plaintext block. Increment the counter. Pass the new counter value and the key to the encryption function. XOR the result of the function with the next ciphertext block. The result is the next plaintext block. Go to step number 5 and repeat until there are no plaintext blocks remaining.

Error propagation NO error propagation

Properties requires a synchronous counter parallelizable no message dependency, but achieves different outputs for like blocks by using the counter requires only a decryption algorithm

Encryption and Decryption

Error Propagation and Properties