Adding XOR function to bigint library
- by Jason Gooner
Hi,
I'm using this Big Integer library for Javascript: http://www.leemon.com/crypto/BigInt.js and I need to be able to XOR two bigInts together and sadly the library doesn't include such a function. The library is relatively simple so I don't think it's a huge task, just confusing.
I've been trying to hack one together but not having much luck, would be very grateful if someone could lend me a hand. This is what I've attempted (might be wrong). But im guessing the structure is going to be quite similar to some of the other functions in there.
function xor(x, y)
{
var c, k, i;
var result = new Array(0); // big int for result
k=x.length>y.length ? x.length : y.length; // array length of the larger num
// Make sure result is the correct array size? maybe:
result = expand(result, k); // ?
for (c=0, i=0; i < k; i++)
{
// Do some xor here
}
// return the bigint xor result
return result;
}
What confuses me is I don't really understand how it stores numbers in the array blocks for the bigInt. I don't think it's a case of simply bigintC[i] = bigintA[i] ^ bigintB[i], then most other functions have some masking operation at the end that I don't understand. I would really appreciate any help getting this working.
Thanks
