The cadastro de pessoas físicas (CPF; Portuguese for natural person register) is the brazilian individual taxpayer registry identification, a number attributed by the brazilian federal revenue to both brazilians and resident aliens who pay taxes or take part
When emitted, the CPF generate a number with eleven digit, the last two digit being verifiers to avoid typing errors. The CPF is an unique number for each taxpay even in case of loss of de card (wikipedia)
The CPF generator uses the module 11 algorithm to calculate the last two digits of the CPF, called verifier digits. They are the ones thas give the basic authenticity for pass on validation of application forms in development.
This tool was developed for programmers and testers who have the constant need to enter different CPF numbers in developing forms.