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Jul
22
comment Lowest number challenge scheme
@fkraiem remember though, you would have to always run the coin-flip (whether there was a tie or not), otherwise you leak whether or not there was a tie. My point is, things can get complicated.
Jul
18
reviewed Approve Polynomial representation of the affine part of the AES S-box
Jul
18
comment Polynomial representation of the affine part of the AES S-box
Could you explain what l0-l8 are? I'm too lazy to read the paper right now.
Jul
18
comment Storing encryption key
Is this a stand alone app, or a client server app?
Jul
17
revised Given $g$, $b$, $g^{ab}$, is finding $g^a$ a hard problem?
rolled back to a previous revision
Jul
17
revised Given $g$, $b$, $g^{ab}$, is finding $g^a$ a hard problem?
Tried to make the computations more explicit.
Jul
17
comment Given $g$, $b$, $g^{ab}$, is finding $g^a$ a hard problem?
In what group is $b^{-1}$ computed?
Jul
15
comment Decrypting an encrypted text out of order
Use a stream cipher
Jul
15
comment Decryption issue with self-coded AES-128
Richie, you are right. I realized that after I typed my comment and just left it. Feel free to roll back if you want.
Jul
15
comment CBC-MAC length extension attack with IV simulation
Are you able to capture many messages or just one? If so, do some of them have your account and the amount 1000000? If you could post example messages, that would be helpful.
Jul
15
comment Ciphertext indistinguishability (IND-CPA) for symmetric cryptography
Not if the IV is changing. That is why the comment I linked to is so important. An encryption algorithm is just a primitive, how are you actually going to use it? That is what you have to define.
Jul
15
comment Ciphertext indistinguishability (IND-CPA) for symmetric cryptography
This comment as well as the answers, etc might interest you.
Jul
15
comment Ciphertext indistinguishability (IND-CPA) for symmetric cryptography
For the first part, the adversary can submit any two messages. So one (or both) could be repeated.
Jul
15
comment CBC-MAC length extension attack with IV simulation
Let me rephrase, when you say "capture a valid message from target user", is that message encrypted + you have the MAC or is it plaintext + you have the MAC?
Jul
15
comment A question about elliptic curves and finite fields in bilinear pairings
What pairing-free scheme are you looking at?
Jul
15
comment Decryption issue with self-coded AES-128
+1 This should be very helpful to the OP. I fixed one minor mistake in your key schedule.
Jul
15
revised Decryption issue with self-coded AES-128
edited body
Jul
15
comment Decryption issue with self-coded AES-128
If I remember right, implementing AES in Java is tricky as Java does not support unsigned integers. It is possible to do, but you could be suffering from this problem.
Jul
15
comment CBC-MAC length extension attack with IV simulation
So let me get this straight, you are given a single message of the form listed above with some number of transactions and a MAC on that message using CBC-MAC. And you are suppose to come up with a new message which extends the original but adds a transfer to yourself and you are suppose to compute the MAC for that new message. Is that correct? Are you given the plaintext of the message or the ciphertext?
Jul
15
comment A question about elliptic curves and finite fields in bilinear pairings
The mathematical disadvantage for $E(F_p)$ as the target group $G_T$ is that no such construction exists.