Uniqueness of WHOIS handles

Is there some method to guarantee the uniqueness of WHOIS handles?
Can I register affixes somehwere?

I'm currently creating a WHOIS-like database (which might be publicly
accessible one day), and I'd like to avoid handle collisions with
other WHOIS databases.

(I asked a similar question on some IETF WHOIS list a few months ago,
but this list appears to be dead.)