3 ms·
Does flipping a bit in the ciphertext not flip the same bit in the plain text, for naive implementations?
by street 9y ago
Does flipping a bit in the ciphertext not flip the same bit in the plain text, for naive implementations?
- dmitrygr 9y agoNo because of SubBytes step
- czinck 9y agoAES and similar algorithms are specifically designed to not do that, because otherwise details of the ciphertext leak details about the plaintext. https://en.wikipedia.org/wiki/Differential_cryptanalysis https://en.wikipedia.org/wiki/Differential_cryptanalysis is about exploiting any unintentional leak of info like that.
- rocqua 9y agoAES in CTR mode does work like that. So do most stream ciphers. Differential cryptanalysis is not about defending against bit-flips. Instead, it is about comparing two cipher texts to learn something about the relation between corresponding plain-text. This is only possible on AES-CTR if you have to ciphertexts with the same key and nonce/IV. This is why a nonce is supposed to be used only once. Same goes for other xor based stream ciphers.