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seen Apr 5 '13 at 6:59

Apr
5
comment How is ElGamal not secure under chosen ciphertext attack, but semantically secure in some cases?
Oh- that helps clear up a lot of things I misinterpreted. Thanks!
Apr
5
comment Chosen ciphertext insecurity in an ElGamal variant
Is it the same result for (g^a(mod p))^k as it is for (g^a)^k(mod p)?
Apr
4
comment Attack on DSA with signatures made with k, k+1, k+2
Just to be clear, if all operations are performed in Z_q, does that mean that if I have something like a - b(mod q), that necessarily means (a-b)(mod q), NOT subtract b(mod q) from a? For example, in the equation from step 3, and some of the other equations along the way
Apr
4
comment Attack on DSA with signatures made with k, k+1, k+2
Ok- that helps a lot. Another question: in 1.2, I can't understand why (mod q) is still in the equation. If I use the rule you've provided in the edit, I eliminate the entire term x*r2(mod q) and am left with only h2-(h1(r2/r1)) so I'm trying to understand why the (mod q) part of the term is still there rather than having the whole term eliminated
Apr
4
comment Attack on DSA with signatures made with k, k+1, k+2
Thanks! There are a few lines I don't understand- might just be that I'm unfamiliar with some modular arithmetic. In step 1, #2, what is the operation being performed? Are we subtracting (1)*[r2/r1]? If so, I don't completely understand where the x gets eliminated. Also, in step 2, #1, it looks like you've rearranged (1) from step 1- is there some property of modulus that allows you to just "swap" the x and the h1/r1 like you did? Would you be able to include exactly what you're adding/subtracting to get each equation so I can follow the math?
Mar
18
comment Solving congruences using PARI
That works- thanks! Both of your answers have been really helpful to me even though you don't use PARI/GP
Mar
18
comment Solving congruences using PARI
I've edited the comment to show how I've attempted to solve the example system of congruence you gave in my last question