3 ms·
I was wondering if using randomly generated shared 1GB or so file as a kind of one-time pad would be useful. Xor data with it using it as circular buffer, do me
by hawski 9y ago
I was wondering if using randomly generated shared 1GB or so file as a kind of one-time pad would be useful. Xor data with it using it as circular buffer, do messages must be of the same length or it will go out of sync.
- mseebach 9y agoIf you reuse your pad, you're vulnerable to frequency analysis, which is literally the oldest trick in the book. You might as well send in plaintext.
- hawski 9y agoHow easy would it be if you would go through the entire 1GB and only then from the beginning? I guess it is a question of how big messages are.
- mseebach 9y agoIf you're only reusing it once, then I guess frequency analysis gets tricky, but the problem you have instead is that you have provided a validation function: Where, using a one-time-pad, any key that yields plausible cleartext is a possible candidate, if you have two cyphertexts encoded with the same (piece of) the one-time-pad, only keys that result in plausible decrypted cleartext for both cyphertexts are possible candidates. This was how an early break-through in breaking the Enigma was achieved (tangentially, as the Enigma isn't a one-time-pad, but the analysis is similar): Codes were rotated daily, but the first message sent out every morning with the new codes was a weather-report. Thus, the team could immediately cull the search-space to keys that would decrypt to "Weather on [date]" for the first n characters.