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Jun
11
comment Does this protocol provide Perfect Forward Secrecy / are there potential security flaws?
Please make sure to provide a specific technical question in the body of the question. The title is for, well, a title -- and does not replace to need to ask a specific question in the body of the question.
Jun
11
answered Comparing two values without revealing them
Jun
10
awarded  Custodian
Jun
10
reviewed Leave Closed ECDSA: Retrieving non-random k
Jun
9
answered How can one detect if a hash function doesn't have a full image?
Jun
8
awarded  Custodian
Jun
7
comment Security of a security protocol for key exchange, using symmetric-key cryptography
OK, I see, I apologize for my misunderstanding.
Jun
7
accepted Obfuscate an “I'll reveal if you do” function
Jun
7
comment Obfuscate an “I'll reveal if you do” function
An interactive commitment protocol would be fine, as long as the verification is non-interactive (given an alleged opening of the commitment from Alice, Bob can check entirely on his own whether it is indeed a valid opening). If this problem gets easier for Naor commitments, that would be fascinating and useful!
Jun
7
comment Obfuscate an “I'll reveal if you do” function
@mikeazo, I don't recall what the standard definition of a commitment scheme is; my recollection is that it doesn't really matter what $V(C(x,r),x,r')$ outputs, if $r \ne r'$ (it could output either $0$ or $1$, and no harm would be done either way).
Jun
7
comment Update to “Cryptographic Right Answers”
@otus, absolutely! You make a very timely and accurate point. The challenge is to find a simpler protocol that one can recommend to developers to provide a secure channel. I'm not aware of one; but maybe you have some suggestions?
Jun
7
comment Obfuscate an “I'll reveal if you do” function
Thank you! Yes, I do have an a-priori bound on the length of $x$ and $y$, so that removes one possible complication. It would be fine to use any commitment scheme that makes the obfuscation task easy, so if Merkle tree based commitments make obfuscation easier, that would be fine.
Jun
6
asked Obfuscate an “I'll reveal if you do” function
Jun
6
comment Attack on a key-exchange,symmetric-key cryptography protocol
I don't understand this answer yet. Are you thinking of gathering this information for all possible values of the nonce? Normally, nonces are chosen to be from a large enough space that such an attack will be wildly impossible: e.g., a nonce might be a random 128-bit number. Would you like to try editing your answer to clarify what attack you had in mind and what security property is violated by your attack?
Jun
5
revised Three different numbers with x³=x mod p
added 49 characters in body
Jun
5
revised Security of a security protocol for key exchange, using symmetric-key cryptography
rolled back to a previous revision
Jun
5
comment Universal Circuits in Indistinguishability Obfuscation Candidate Construction
I don't know. Maybe the security proof requires use of the universal circuit? (e.g., to ensure the branching program will have the same structure regardless of what the original circuit is, or something)
Jun
3
comment Theory for pre-paid debit card: card-to-card transfer
That's one kind of approach. The other kind is to use a coin-based scheme for e-cash, e.g., Chaum-style e-cash (based upon blind signatures).
Jun
3
answered Theory for pre-paid debit card: card-to-card transfer
Jun
3
comment Theory for pre-paid debit card: card-to-card transfer
What research have you done?