Re: Creating unique, non-reproducible serial ID

Nior,

> I'm looking for an algorithm to create a serial ID that I can give to
 users,
> encrypted in a away that they will not be able to recreate other serial
IDs.

Here's an old method:

Use a sequence generator to generate sequential 12 digit ID's. Use a CRC type hashing algorithm to generate a 4 digit hash. The hashing function could have a built in private key, in order to make the hashing function harder to crack.

Concatenate the 12 digit serial id with the 4 digit hash function to produce a 16 digit id.

The chances of generating a correct key at random are about 1 in 10,000.

Avoiding cracking of your hashing function by a determined cracker is harder.

--
Regards,
    David Cressey
    www.dcressey.com