This document specifies procedures, independent of the transmission process, for protecting the integrity of transmitted financial-service-related messages and for verifying that a message has originated from an authorized source, or that stored data has retained integrity. A list of block ciphers approved for the calculation of a message authentication code (MAC) is also provided. The authentication methods defined in this document are applicable to stored data and to messages formatted and transmitted both as coded character sets or as binary data.This document is designed for use with symmetric algorithms where both sender and receiver use the same key. It does not specify methods for establishing the shared key. Its application will not protect the user against internal fraud perpetrated by the sender or the receiver, nor against forgery of a MAC by the receiver.