Abstract: In a cryptographic module, a User Defined Function (UDF) facility is provided which provides users with the capability of defining and creating custom functions to meet their cryptographic processing needs. The cryptographic module is contained within a physically and logically secure environment and comprises a processing unit and memory connected to the processing unit. The memory includes code for translating User Defined Functions (UDFs) into a machine-readable form and at least one command for operating on the UDFs. The UDFs are loaded into and executed in the secure area of the cryptographic module without compromising the total security of the transaction security system.

Abstract: A system for determining when a remote computer user is authorized to communicate with a host computer and to establish a ciphering key to be used for the communications session. A random number is generated at the host computer, ciphered under the user's PIN, and sent to the remote user where it is deciphered under the PIN to provide a session key. In one embodiment, this key is reciphered under the PIN, sent to the host computer, and deciphered under the PIN. The deciphered value is equal to the generated random number when the correct PIN's are used, thereby validating the user. In another embodiment, the deciphered random number at the remote user location is used as a key to cipher the PIN which is sent to the host, deciphered under the random number, and compared with the PIN existing at the host. Subsequent, ciphering can use the determined session key as a ciphering key.