I wish to generate registration codes for users of software.
The users software has an embedded unique INT known by me
int user = 12345678;
Now I have a fixed key INT known only to me
int key = 19673215;
How would I write an algorithm to generate ascii passwords for the users to enter, (when emailed to them).
And an algorithm within the program to check that the supplied password is valid for the unique user ID int.
This not on UNIX so crypt is not an option and I want to do something a bit more exotic than XOR.
Can anybody help??????
Some workable C code examples only please