Transparently securing data for transmission on financial networks

Systems and methods for performing financial transactions are provided. In one embodiment, the invention provides a method for processing token data for a bank card transaction, the method includes: receiving a string of first token data from a token at a token reader; modifying the first token data and generating second token data, the second token data including modified token data; performing a modulo arithmetic operation on the second token data and determining a mod 10 check digit that will cause a modulo arithmetic check of the second token data to yield the same result as the modulo arithmetic check would yield on the first token data; and inserting the mod 10 check digit in the second data string and forwarding the second data string for the transaction.