A 16-digit hashing function

Question

Is there a hash function that returns a 16-digit hex value (as MD5 returns 32-digit), or is there a library (for C++) in which I can use MD5 or SHA-1 which returns a 16-digit value

Answer 1

Since you're willing to live with the much-higher collision rate, you can just truncate the MD5 hash of the data.

Answer 2

is there a library (for C++) in which I can use MD5 or SHA-1 which returns a 16-digit value

Lookup the OpenSSL crypto library (free) or RSA BSAFE (paid).