how many rfid tags do you expect to process ,you realise of couse that that chip has only 256 bytes of eprom (ie 25 tags)
where does the pin value come from and how is linked to the rfid tag?
and surely once a tag has "voted" it needs to be removed from the active list ?????
for 25 tags its hardly worth the effort except maybe as an educational exercise

LABOR RATES
Normal………………………………$12.50
If you wait…………………………..$15.00 per hour
If you watch………………………..$20.00 per hour
If you help………………………….$30.00 per hour
If you worked on it first………..$50.00 per hour

Deposit $1 x 2^(32-days to deadline)