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Jul
9
comment How to crack SHA256 only letters
rainbow tables, dictionary attack, brute force; the first think you need to figure out is if it uses a salt. that will be important.
Jul
9
comment Are all stream-ciphers IND-CPA?
okay, I can buy the "vigenere cipher didn't use an IV/nonce" explanation. I still think there would have to be some basic security assumptions you would have to place on the stream cipher to make the implication. The theorem in the book assumes $F$ is a pseudorandom function, but that is for the block cipher.
Jul
9
comment Are all stream-ciphers IND-CPA?
I think I am missing something here. Vigenere cipher is a stream cipher, but obviously not IND-CPA as it fails even more basic security definitions. What am I missing about your question?
Jul
8
revised RSA algorithm assignment
edited tags
Jul
8
comment AES-Paillier Homomorphic encryption
You cannot implement AES homomorphically using Paillier. I suggest instead of starting with a solution to a particular problem and asking questions about it, describe your problem and ask for valid solutions, with strengths and weaknesses.
Jul
7
reviewed Approve Quantum computing vs AES s-box equation
Jul
7
answered AES + CBC encryption for a stream of UDP packets
Jul
7
comment AES + CBC encryption for a stream of UDP packets
packets are "usually multiple of the block size of AES"? You can't say usually then say that you "have no need whatsoever for padding".
Jul
7
comment Reversing Rotation + XOR
Cross-posted on math.SE, where there is an update. Cross-posting is against SE rules. Pick one site and stick with it.
Jul
7
comment Weakening of Pallier cryptosystem due to ciphertext equivalence and order in CryptDB
Another thought, we know that knowing two ciphertexts that encrypt the same plaintext cannot leak information about the private key as any adversary with the public key can construct such encryptions. So, the only possibilities is that it leaks information about either the message itself or the randomness values used.
Jul
7
comment Weakening of Pallier cryptosystem due to ciphertext equivalence and order in CryptDB
I don't think it does weaken the paillier cryptosystem. Paillier has been used in situations (e.g., voting), where the plaintext space is $\{0,1\}$. In those applications, picking two ciphertexts, you have a pretty good chance of getting two that encrypt the same message. Yet these applications remain secure. That is the best I can give you right now, however. It will be interesting to see if someone finds a paper that proves this.
Jul
5
comment In what cases will RSA not work?
This contains some related information crypto.stackexchange.com/questions/1004/…
Jul
5
revised Where is SRP-Z from?
edited title
Jun
30
comment Simulation aborted because the adversary doesn't use the random oracle
@Yehuda Welcome to the site. I've read a number of your papers in the past. Glad to have you here.
Jun
30
comment Simulation aborted because the adversary doesn't use the random oracle
I created a chat room we can all use to discuss this more.
Jun
30
comment Simulation aborted because the adversary doesn't use the random oracle
I don't understand how the adversary knows what the result should be but the simulator doesn't for incorrect (w/o RO) ciphertexts.
Jun
30
comment Simulation aborted because the adversary doesn't use the random oracle
So it is predictable even without the special key? But impossible for the simulator to generate something that follows the predictability? In the real world, can one detect that the ciphertext is does not use the correct hash function?
Jun
30
comment Simulation aborted because the adversary doesn't use the random oracle
Good question. I hope someone here can answer. From the adversary's point of view, given a specific input is the output of the alteration oracle predictable? If not, could you just return a random "ciphertext"?
Jun
29
comment Ideas for non duplicate cryptographically secure numbers
Use a cryptographically secure random number generator and generate 128-bit random numbers.
Jun
29
comment ElGamal scheme attack when one message is known and ciphertexts are intercepted
Why should I help someone named cryptohater? :)