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seen Sep 29 at 19:15

Kids in rectangles irritating sick urchins rattling foxes, directory.kirisurf.org lol


Oct
27
comment Random session key + predictable IV
One key is used for one side of a connection. The key initialization function is called once for each side.
Oct
13
awarded  Commentator
Oct
13
comment Random session key + predictable IV
My system as it is does not verify integrity at all. This is really bad, I know it. I'm not sure how exactly it may lead to attacks though. Also, how long should a MAC ideally be? SHA-256 seems to be a bit overheady for things like, kilobyte-sized records.
Oct
13
comment Random session key + predictable IV
My thing uses OFB and treats the data as one ginormous stream, without the notion of "records" as in TLS. Obviously, integrity may be an issue, and I'll look into schemes like GCM. I can't find functions for GCM in the libcrypto docs though.
Oct
13
comment Random session key + predictable IV
The key is only scheduled once per connection. Does this mean I can use the same IV over and over with different keys?
Oct
13
comment Random session key + predictable IV
How do you differentiate between "each to-be-encrypted plaintext"? I'm using OFB mode FYI.
Oct
13
asked Random session key + predictable IV
Mar
28
awarded  Student
Mar
26
comment Is this hand cipher any more secure than the Vigenère cipher?
Using a 0-9 key eliminates the need to write or memorize a huge tabula recta.
Mar
26
comment Is this hand cipher any more secure than the Vigenère cipher?
Also, I thought that Vigenère's main weakness was ciphertext-only attacks, not known or chosen plaintext attacks. Also, I don't see how known-plaintext will help. Chosen would certainly help in decryption.
Mar
26
comment Is this hand cipher any more secure than the Vigenère cipher?
That keystream is enough to decrypt other texts of the same length. AAAAA does not encrypt to the first 5 letters of AAAAAAAAAAAAA encrypted.
Mar
26
comment Is this hand cipher any more secure than the Vigenère cipher?
Actually I was wrong. The keystream is discoverable by encoding "AAAAA...". However, there is little discernable pattern in such a keystream, and avalanche changes happen when the length is changed. Try guessing the key from this keystream: "OAHYCSRLEQTCUCPAECRAOBWYAZCBSFCWAXCUMXAU"
Mar
26
comment Is this hand cipher any more secure than the Vigenère cipher?
Try to decode with the null key to the correct number of rounds, and then decode with the keystream found by encoding AAAAAAA. It is easy to see this does not work.
Mar
26
revised Is this hand cipher any more secure than the Vigenère cipher?
edited tags
Mar
26
comment Is this hand cipher any more secure than the Vigenère cipher?
No, if I attempt to decode with a null key, eventually the keystream will be mangled and pseudo-non-periodic. Note that the keystream is not permuted in each round.
Mar
26
asked Is this hand cipher any more secure than the Vigenère cipher?
Mar
25
awarded  Supporter