network profile
| bio | website | |
|---|---|---|
| location | France | |
| age | 39 | |
| visits | member for | 3 months |
| seen | Mar 27 at 15:44 | |
| stats | profile views | 0 |
Interested in compression algorithms
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Feb 23 |
revised |
From hash to Cryptographic hash added 753 characters in body |
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Feb 23 |
revised |
From hash to Cryptographic hash added 753 characters in body |
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Feb 23 |
comment |
From hash to Cryptographic hash I've edited the question to explained the proposed solution. Reading your comment, it seems you also found better solutions, which work with a better probability than 50%. I would be glad if you could give some hint how they work. |
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Feb 23 |
revised |
From hash to Cryptographic hash added 360 characters in body |
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Feb 23 |
revised |
From hash to Cryptographic hash added 235 characters in body |
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Feb 23 |
revised |
From hash to Cryptographic hash deleted 94 characters in body |
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Feb 23 |
revised |
From hash to Cryptographic hash added 354 characters in body |
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Feb 23 |
revised |
From hash to Cryptographic hash added 254 characters in body |
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Feb 23 |
awarded | Editor |
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Feb 23 |
revised |
From hash to Cryptographic hash added 254 characters in body |
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Feb 23 |
comment |
From hash to Cryptographic hash OK, i think i have a candidate solution for collision, but it's not an easy one, it comes with many restrictions, some of which are not controllable by the attacker. Anyway, here are the candidate modifiers : at position $P$, add $0xBD1C0000$, and then at position $P+4$, add $0x80000000$. I will edit the question to present the associated restrictions (it's not working for any $P$) |
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Feb 22 |
awarded | Scholar |
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Feb 22 |
accepted | From hash to Cryptographic hash |
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Feb 22 |
comment |
From hash to Cryptographic hash OK, thanks, maybe i've got it now. Let's target $B$ = 0x80000000 ? This way $B$ * Prime1 = $B$. And $B + B$ = 0. In this case, $A$ = $B$ >>13 = 2^18. So the problem is reduced as finding $C$ such as $C$ * Prime2 = $A$ = 2^18. |
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Feb 22 |
comment |
From hash to Cryptographic hash Yes, sure, in this case a solution would be easy. It would be possible to create a A, and then -A. The problem is, this is not the full line of operations. The full line is : v1 += XXH_LE32(p) * PRIME32_2; v1 = XXH_rotl32(v1, 13); v1 *= PRIME32_1; Operations 1 alone would match your hypothesis, Operation 2 makes it more complex but i feel it would still be possible to find a solution; but operation 3 (v1 *= PRIME32_1;) seems to scramble everything. I don't see how it could be made "independant of X", which is the whole point. |
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Feb 21 |
comment |
From hash to Cryptographic hash That looks like an excellent answer. The principles which make xxHash not suitable for MAC usage seem identical to those targeting MurmurHash : mainly, the claim is that it is possible to forge 2 consecutives sequences which will cancel each other, whatever the underlying internal state is, making this operation independant of the secret key. I would feel better, nonetheless, if i could find such consecutive sequences. |
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Feb 21 |
awarded | Supporter |
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Feb 21 |
comment |
From hash to Cryptographic hash Thanks for clarifying, the difference between cryptographic Hash and MAC is much better now. |
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Feb 21 |
comment |
Is there a way to analyse xxHash and tell, either by human analysis, or with an automated tool, that this hash function is or is not cryptographic? It is a duplicate now, due to the migration. Main question is there : crypto.stackexchange.com/questions/6408/… |
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Feb 21 |
comment |
From hash to Cryptographic hash "secret key" = "seed" |
