An avalanche effect is also desirable for the key: A one-bit change in a key should result in a dramatically different ciphertext if the plaintext is unchanged.
Assume an encryption with a given key. Now assume the key bit at position 1 (prior to PC−1) is being flipped. Which S-boxes in which rounds are affected by the bit flip during DES encryption?
Which S-boxes in which DES rounds are affected by this bit flip during DES decryption?
I know the first bit flips to the eighth after the PC-1 function. After that, I'm lost on how to track the bit through 16 rounds of DES.
