ACOS1 Security Features: 

Digital Encryption Standard (DES) -- Ciphering is used in this mode of protection, which is like translating the information into some unknown foreign language, so the stored information can be transmitted confidentially. Simple DES or Triple DES versions are both available. 

Message Authentication Capability (MAC) -- This is based on the exchange and mutual verification of secret passwords [keys] between the card and the card-accepting device. The whole verification process is done within the device and information is never transmitted outside during the process, making eavesdropping virtually impossible. 

Enforced Message Authentication with random numbers and dedicated key pair. 

Continuous system integrity checks guarding against attempted security breaches. 

Five secret codes + Issuer Code + Pin to selectively enable access to data stored in card and to features and functions provided by the card e.g. the READ and WRITE commands. 

Account Transaction Processing (ATP) provides dedicated data structure for payment applications with CREDIT, DEBIT, INQUIRE ACCOUNT commands for secure transaction processing. 

Other Features 

Compliant with ISO 7816-1/2/3 

Issuer definable file structure for convenient and efficient memory management. 

Users can choose single DES or triple DES for encryption algorithm.