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Dec
15
revised Attack against modular inversion operation using side-channels?
Added suggested clarifications
Dec
15
comment Attack against modular inversion operation using side-channels?
He may be able to measure computing time. He does not have access to the output nor to the modulus. He knows only the value that will be inverted.
Dec
15
accepted Can one use a Cryptographic Accumulator to efficiently store Lamport public keys without the need of a Merkle Tree?
Dec
15
asked Attack against modular inversion operation using side-channels?
Dec
10
answered Can one use a Cryptographic Accumulator to efficiently store Lamport public keys without the need of a Merkle Tree?
Dec
10
asked Can one use a Cryptographic Accumulator to efficiently store Lamport public keys without the need of a Merkle Tree?
Dec
10
accepted How hard is to invert the function that computes the middle-bits of (x^2)?
Dec
4
comment How hard is to invert the function that computes the middle-bits of (x^2)?
The brute-force attack is obviously a upper bound in the number of computations. It does not help me much to known how much time an attacker will require to invert it.
Dec
2
comment How hard is to invert the function that computes the middle-bits of (x^2)?
Also I'm interested in the number of logic gates it takes to implement the inversion circuit, as compared to the number of logic gates it takes to compute f.
Dec
2
asked How hard is to invert the function that computes the middle-bits of (x^2)?
Nov
15
comment Are there any bijective one-way functions not based on number-theoretic hardness assumptions?
I said clearly in the question that I needed a practical computing difference between F and F^-1, not unfeasibility. Maybe the question does not belong to crypto, then where?
Nov
15
revised Are there any bijective one-way functions not based on number-theoretic hardness assumptions?
Adds nothing
Nov
15
comment Are there any bijective one-way functions not based on number-theoretic hardness assumptions?
What about making the word length big enough, like using a T-function of 64 bits in a 64-bit CPU? I think inverting it may take at least k*64 machine instructions, while generating it may take only 3 instructions. E.g. F(x) = x + (x^2 v 5)
Nov
15
comment Are there any bijective one-way functions not based on number-theoretic hardness assumptions?
Ok. so shuffling adds nothing.
Nov
14
revised Are there any bijective one-way functions not based on number-theoretic hardness assumptions?
Text was misleading. Badly written.
Nov
14
comment Are there any bijective one-way functions not based on number-theoretic hardness assumptions?
If you agree, then I will edit the answer to reflect these ideas.
Nov
14
comment Are there any bijective one-way functions not based on number-theoretic hardness assumptions?
Yes. My answer was missing some info. I said "using" a T-function, but I didn't said how. Let T1.. Tn be T-functions. Let S1..Sn be fixed bit-shuffles. Then F=(T1 o S1 o T2 o S2 .... Tn o Sn) should be hard to invert. What do you think?
Nov
14
accepted Are there any bijective one-way functions not based on number-theoretic hardness assumptions?
Nov
14
answered Are there any bijective one-way functions not based on number-theoretic hardness assumptions?
Nov
11
comment Are there any bijective one-way functions not based on number-theoretic hardness assumptions?
The function is for a special kind of Proof-of-work. Currently I'm using a hash function using the subset of invertible values of the domain. But this is far from perfect.