Smart cards have received a lot of media attention lately, including major marketing programs by certain credit card vendors, including the large marketing campaign launched by American Express surrounding the new "American Express Blue" card which, like all smart cards, features an integrated circuit instead of just the traditional magnetic strip. Smart cards can be used for several purposes, including as credit card replacements or similarly as electronic wallets. Electronic wallets differ from credit cards wherein the former "transaction cards" require a vendor to contact a remote system to verify and confirm the transaction, electronic wallets are more similar to debit cards with the amount of money remaining actually contained on the card. Given that smart cards have what amounts to a miniture, portable computer on them, they can also be used as a "black box" to carry out proprietary calculations or more importantly, to contain a security token for authentication with a trusted system. These tokens can be updated upon each use with a non-reversible algorithm.