Abstract: This disclosure relates to a method and apparatus for improving the security of credit card transactions. It involves a so-called "smart" credit card, which includes a processor, a memory, and a display window. When used, the card produces a verification number, which is based on a transaction sequence number and an encryption algorithm stored in the memory of the card. The verification number produced by the card is read in the display window and transmitted to a verification computer. The computer uses the verification number, together with a de-encryption algorithm, to produce a computed transaction sequence number. If the computed transaction sequence number corresponds to a transaction sequence number stored in the memory of the computer, then the computer will authorize the transaction, otherwise it will not.