4 ms·
One could always add a random length of random bytes to the message so the size comparison method doesn't work. This assumes that real ciphertext is indistingu
by adamsmith 17y ago
One could always add a random length of random bytes to the message so the size comparison method doesn't work.
This assumes that real ciphertext is indistinguishable from random data without the key.
- derefr 17y agoReal cyphertext should have less Shannon entropy/higher compressability than random data, I think, unless a one-time pad was used. However, it's fully possible to create semi-random cyphertext to a set entropy, which means all your encrypted transmissions could just be filled with "sparse" or "dense" extra data to balance them out with your chosen "inconspicuous" entropy value. Then again, I seem to recall that the cyphertext is compressed before encryption in PGP/GPG, likely in order to obviate exactly this problem. Then you would indeed just have to add white noise to the messages until their post-compression, pre-encryption filesizes match, as hopefully the encryption layer won't allow the compression ratio information to leak through.