Abstract: A data security device which includes storage means for storing a master cipher key, cryptographic apparatus for performing cryptographic operations and control means for controlling the writing of a master cipher key into the storage means, controlling the transfer of the master cipher key to the cryptographic apparatus and controlling the cryptographic apparatus to perform cryptographic operations. When a new master cipher key is written into the storage means, the old master cipher key is automatically overwritten with an arbitrary value, after which the new master key may be written into the storage means. The cryptographic apparatus of the data security device includes storage means, a cipher key register and cipher means for performing a cipher function on data stored in the cryptographic apparatus storage means under control of a working cipher key stored in the cipher key register with the resulting ciphered data being stored in the cryptographic apparatus storage means.

Abstract: A file security system for data files associated with a host data processing system. The host system includes a data security device which contains a secure host master key and is capable of performing a variety of cryptographic operations. At initialization time, the host system generates a series of file keys for the associated storage media and protects them by enciphering the file keys under a variant of the host master key. When a data file is to be created, a random number is generated and defined as an operational key enciphered under the file key of a designated storage media. The host data security device, using the enciphered file key of the designated storage media, transforms the enciphered operational key under control of the host master key into a form which permits the operational key to be used for enciphering host data.

Abstract: A communication security system for data transmissions between remote terminals and a host system. The remote terminals and the host system include data security devices capable of performing a variety of cryptographic operations. At initialization time, a host master key is written into the host data security device and the host system generates a series of terminal master keys for the remote terminals. Protection is provided for the terminal master keys by enciphering them under a variant of the host master key. The terminal master keys are then written into the data security devices of the respective remote terminals to permit cryptographic operations to be performed. When a communication session is to be established between a designated remote terminal and the host system, a random number is generated and defined as an operational key enciphered under the host master key which permits the operational key to be used at the host system for enciphering or deciphering data operations.

Abstract: A communication security system for data transmissions between different domains of a multiple domain communication network where each domain includes a host system and its associated resources of programs and communication terminals. The host systems and communication terminals include data security devices each having a master key which permits a variety of cryptographic operations to be performed. When a host system in one domain wishes to communicate with a host system in another domain, a common session key is established at both host systems to permit cryptographic operations to be performed. This is accomplished by using a mutually agreed upon cross-domain key known by both host systems and does not require each host system to reveal its master key to the other host system.

Abstract: A message transmission system for the secure transmission of multi-block data messages from a sending station to a receiving station.The sending station contains cryptographic apparatus operative in successive cycles of operation during each of which an input block of clear data bits is ciphered under control of an input set of cipher key bits to generate an output block of ciphered data bits for transmission to the receiving station. Included in the cryptographic apparatus of the sending station is means providing one of the inputs for each succeeding ciphering cycle of operation as a function of each preceding ciphering cycle of operation. As a result, each succeeding output block of ciphered data bits is effectively chained to all preceding cycles of operation of the cryptographic apparatus of the sending station and is a function of the corresponding input block of clear data bits, all preceding input blocks of clear data bits and the initial input set of cipher key bits.