The size of the random string doesn't make much difference at all. It is actually the size of the seed that matters. Or, more precisely, the number of random bits in the output.

If you generate a 32-bit seed using methods that really only give you about 8 bits worth of randomness and then generate a 45KB string, then you still have about a 1/256 chance of generating the same string next time.

And this problem doesn't go away when you use MD5 -- you still need to generate unique strings.

Also, the "secret" with a random string is how you generated it. If that gets out, then people can still spoof sessions.

        - tye (but my friends call me "Tye")