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Re: crypto technique
Matthew J Ghio wrote:
>we can mod each term by 256. Which gives:
>
> 4 3 2
>y = (.125x + .25x + 63.875x + 63.75x + 223) mod 256
>
>which still produces the same values for y, but the factoring technique fails.
I still don't know about that - I think all it does is remove the
problem one step from immediately solvable.
Is that P term public knowledge (here P = 256)? If so, the revised
equations are:
c1/2 + 1/4 = 63.75 ===> c1 = 127
c1/2 + 1/4 x1^2 + c2 = 223 + 256k ===> c2 = -7905 + 256k
And this will yeild either c2 = -225 or c2 = 31. The computational
expense of trying both is small.
If it does turn out that the magnitude of the constants must be less
than P, I don't think taking the mod of each coefficient obscures the
problem very much at all. It still boils down to solving systems
of simultaneous equations, which isn't the same complexity as solving
discrete logarithms or factoring.
--
Karl L. Barrus: [email protected]
keyID: 5AD633 hash: D1 59 9D 48 72 E9 19 D5 3D F3 93 7E 81 B5 CC 32
"One man's mnemonic is another man's cryptography"
- my compilers prof discussing file naming in public directories