tylo

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	223 reputation	bio	website		visits	member for	8 months
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17h	comment	How do zero knowledge protocol with vertex-3-coloring work? @moose I am not entirely sure, how to solve that question but I think the random graph generation works. But I do not have any proofs or numbers to back this up. You would have to estimate the proportions between those special cases and the general case, and if the probability for a hard instance is an overwhelming function. Or equally, if the probability for special cases is negligible
17h	comment	How do zero knowledge protocol with vertex-3-coloring work? Commitments are cryptographic primitives, which can hide its content. Basically they are like locked boxes. And later they can be opened and reveal what was inside. The point is, that the verifier can decide which boxes should be opened, and the prover can not modify the boxes based on this decision.
17h	comment	Recommended authenticated stream cipher for minimum overhead? Small correction: Meet in the middle transforms the complexity from $O(2^n)$ time and $O(1)$ space to $O(2^{n/2})$ and $O(2^{n/2})$ space, where n denotes the bitlength of the MAC.
17h	comment	Recommended authenticated stream cipher for minimum overhead? To answer your question: There is no way to keep integrity and reducing the size of the MAC. 4 byte MAC means $\frac{1}{2^{32}}$ probability for a correct guess. This is independent of the actual algorithms used and is the upper bound for it. For almost any algorithm, "meet in the middle" works just fine, which changes the computational time from $2^{32}$ to $2^{16}$ time and $2^{16}$ space.
Jun 14	comment	Recommended authenticated stream cipher for minimum overhead? That's a bad idea. Using only parts of the HMAC is a loss of integrity. Assuming the attacker knows the message is only 1 byte long. He still can not test these $2^8$ possibilities and find a correct HMAC , because he does not know $k$. If you use only part of the HMAC, his chance of random guessing went up to non-neglectible probability.
Jun 14	answered	How do zero knowledge protocol with vertex-3-coloring work?
Jun 14	answered	Algorithm: How to use x and y mouse movement co-ordinates to generate random data?
Jun 13	comment	Can ElGamal encryption and ElGamal signatures be used together sharing the same key-pairs? DSA is not more "secure" than ElGamal signatures, because they are essentially the same computations with different names. The only difference is that DSA operates on a subgroup of cardinality q, while ElGamal operates on all p-1 with the annotation "p-1 needs at least one large prime factor". Otherwise they are the same. This is also the reason for smaller signatures, so that q matches the number of possible hash-outputs. If you rather follow the ElGamal algorithm and replace every "p-1" with "q" and choose the generator appropriately (cardinality q), they are the same.
Jun 12	comment	Have these compositions of block ciphers the same security? I agree, the differences between encryption and decryption are small enough, that the security should be almost the same.
Jun 10	answered	How long to bruteforce a RSA key
Jun 10	answered	Have these compositions of block ciphers the same security?
Jun 10	comment	Is triple des similiar to RSA in that they message size is limited to the key size? Triple DES and RSA are not both block ciphers. The question was not about AES.
Jun 10	revised	Is triple des similiar to RSA in that they message size is limited to the key size? added 190 characters in body
Jun 10	comment	Is triple des similiar to RSA in that they message size is limited to the key size? poncho, you are right, of course. The block size is fixed and the key size supports the other formats. However, AES also has a limited size (without MoO), in contrast to the assumption in the question.
Jun 6	answered	Is triple des similiar to RSA in that they message size is limited to the key size?
Jun 4	comment	Why crypto hash functions must be collision resistant and how to find resistant? A cryptographic hash function is defined as a hash function (fixed output length) which is collision resistant and pre-image resistant. I do not see any circular arguement. If HMAC need a cryptographically hash function or not is entirely irrelevant.
Jun 4	comment	Why crypto hash functions must be collision resistant and how to find resistant? The question was for hash functions and collision resistance, not for digital signatures.
Jun 4	awarded	Commentator
Jun 4	comment	Why crypto hash functions must be collision resistant and how to find resistant? Beside the difficulty of finding a collision or preimage, "hash and sign" is just one application of hash functions. The question seems to be more general, as "why do you need this stuff at all?"
May 24	awarded	Critic