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Feb
13
asked Threshold Signatures for RSA and DSA
Feb
3
comment What type of hash functions provides non-malleability of hash digests?
I think so. It is sort of a deterministic version of $\mathcal{H}(r\|\mathcal{H}(m))$ or $\mathcal{H}(r_2\|\mathcal{H}(r_1\|m))$ which have been studied in designing message authentication codes. Once again, it isn't provably non-malleable, but in practice should eliminate the length-extension attack.
Feb
3
comment Why RSA encryption key is based on modulo $\varphi(n)$ rather than modulo $n$
Thanks. I see why it was incorrect before.
Feb
2
revised commitments wiki description
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Feb
2
suggested rejected edit on commitments tag wiki excerpt
Feb
2
suggested approved edit on commitments tag wiki
Feb
2
wiki created commitments description
Feb
2
revised Is there a cumulative commitment scheme?
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Feb
2
revised What type of hash functions provides non-malleability of hash digests?
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Feb
2
answered What type of hash functions provides non-malleability of hash digests?
Feb
1
answered Why RSA encryption key is based on modulo $\varphi(n)$ rather than modulo $n$
Jan
30
answered Are there two known strings which have the same MD5 hash value?
Jan
30
comment Salts, how does the script know what the salt is?
Thanks @Paulo and @Thomas; good points. I fixed my answer.
Jan
30
revised Salts, how does the script know what the salt is?
added 36 characters in body
Jan
30
comment Proving knowledge of a preimage of a hash without disclosing it?
The hash design needs to be known so both parties can follow the progress through the circuit. I don't think we can always have something real-world practical (it isn't claimed in the talk that we can; only that we can for SHA-1). It depends on how well the function lends itself to certain tricks for speeding up the proof. What he did was as much art as science in converting SHA-1 into a blend of boolean/arithmetic circuitry.
Jan
30
comment Proving knowledge of a preimage of a hash without disclosing it?
An unbounded Alice can always prove. A bounded Alice can only prove when the circuit complexity of the hash has the same bound. A real-life Alice can only prove if she can generate a relatively simple description of the circuit with operations that have efficient zero-knowledge proofs. The latter is the case with SHA-1, but necessarily other hash functions.
Jan
30
answered Salts, how does the script know what the salt is?
Jan
30
comment Proving knowledge of a preimage of a hash without disclosing it?
The protocol can allow Bob to distinguish $H$ from a random oracle, but it requires Alice's input. I don't think that contradicts indistinguishability. For example, Elgamal is IND-CPA-secure but also admits proofs of plaintext knowledge. Alice could allow Bob to distinguish ciphertexts he couldn't on his own. In any case, no implemented hash function can act as a random oracle in the real world.
Jan
30
answered Proving knowledge of a preimage of a hash without disclosing it?
Jan
27
revised Provable Encryption
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