International Business Machines Corporation

William F Ehrsam

Carl H Meyer

Walter L Tuchman

John L Smith

Stephen M Matyas

Robert C Elander

Robert Lowell Powers

Paul N Prentice

Jonathan Oseas

Richard E Lennon

Richard J Sahulka

Lloyd L Hollis

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. A load cipher key direct function can be performed whereby a working cipher key may be loaded directly into the cipher key register for use as a working cipher key in performing a cipher function. A decipher key function can be performed whereby the master cipher key is transferred to the cipher key register as a working cipher key after which an operational key enciphered under the master cipher key is transferred to the cryptographic apparatus storage means and the control means causes the enciphered operational key to be deciphered to obtain the operational key in clear form as a working cipher key for subsequent encipher/decipher data functions.

Cryptographic communication and file security using terminals

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. The host data security device, using the enciphered master key of the designated remote terminal, transforms the enciphered operational key under control of the host master key into a form in which the operational key is enciphered under the terminal master key of the designated remote terminal. The operational key enciphered under the terminal master key of the designated remote terminal is transmitted to the remote terminal to permit the enciphered operational key to be used at the remote terminal for enciphering or deciphering data operations.

Cryptographic communication security for single domain networks

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. The operational key enciphered under the file key of the designated storage media, as header information, together with the host data enciphered under the operational key is written on the storage media as an enciphered data file. When the data file is recovered, the host data security device, using the enciphered file key of the designated storage media, transforms the enciphered operational key header information under control of the host master key into a form which permits the operational key to be used for deciphering the enciphered data file to obtain the file data in clear form.

Cryptographic file security for single domain networks

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. The cross domain key is enciphered under a key encrypting key designated as the sending cross domain key at the sending host system and under a different key encrypting key designated as the receiving cross domain key at the receiving host system. The sending host system creates an enciphered session key and together with the sending cross-domain key performs a transformation function to reencipher the session key under the sending cross domain key for transmission to the receiving host system. At the receiving host system, the receiving host system using the receiving cross-domain key and the received session key, performs a transformation function to reencipher the received session key fron encipherment under the sending cross domain key to encipherment under the receiving host system master key. With the common session key now available in usable form at both host systems, a communication session is established and cryptographic operations can proceed between the two host systems.

Cryptographic communication security for multiple domain networks

A file security system for data files created at a first host system in one domain and recovered at a second host system in another domain of a multiple domain network. Each of said host systems contain a data security device provided with multiple host keys capable of performing a variety of cryptographic operations. Creation and recovery of a secure data file is accomplished without revealing the keys of either of the host systems to the other of the host systems. When the data file is to be created at the first host system, the first host system data security device provides a file recovery key for subsequent recovery of the data file at the second host system and enciphers first host system plaintext under a primary file key, which is related to the file recovery key, to obtain first host system ciphertext as the data file. The file recovery key is used as header information for the data file or maintained as a private file recovery key. When the data file is to be recovered at the second host system, the file recovery key is provided at the second host system and the second host system data security device performs a cryptographic operation to transform the file recovery key into a form which is usable to decipher the data file. The second host system data security device then uses the transformed file recovery key to perform a cryptographic operation to obtain the first host system ciphertext in clear form at the second host system.

Cryptographic file security for multiple domain networks

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.

Message verification and transmission error detection by block chaining

A device for ciphering a block of data bits under control of a cipher key. The cipher device performs a ciphering process for the block of data by carrying out an operation in which the block of data bits is first expanded by duplicating predetermined ones of the data bits. The data bits of the expanded block are combined by modulo-2 addition with an equal number of cipher key bits, selected in accordance with an arbitrary but fixed permutation, to produce a plurality of multi-bit segments forming the arguments for a plurality of different nonlinear substitution function boxes. The substitution boxes perform a plurality of nonlinear transformation functions to produce a substitution set of bits which are equal in number to the number of data bits in the first half of the message block. The substitution set of bits is then subjected to a linear transformation in accordance with an arbitrary but fixed permutation. The combined nonlinear transformation and linear transformation results in a product block cipher of the block of data.

Product block cipher system for data security

A device for ciphering message blocks of data bits under control of a cipher key. The cipher device performs an enciphering process for each message block of data by carrying out a predetermined number of iteration operations in the first of which a first half of the message block of data bits is first expanded by duplicating predetermined ones of the data bits. The data bits of the expanded message block are combined by modulo-2 addition with an equal number of cipher key bits, selected in accordance with an arbitrary but fixed permutation, to produce a plurality of multi-bit segments forming the arguments for a plurality of different nonlinear substitution function boxes. The substitution boxes perform a plurality of nonlinear transformation functions to produce a substitution set of bits which are equal in number to the number of data bits in the first half of the message block. The substitution set of bits is then subjected to a linear transformation in accordance with an arbitrary but fixed permutation. The combined nonlinear transformation and linear transformation results in a product block cipher of the first half of the message block. The second half of the message block is then modified by modulo-2 addition with the product block cipher of the first half of the message block to produce a modified second half of the message. The modified second half of the message block then replaces the first half of the message block which at the same time replaces the second half of the message block in preparation for the next iteration operation. During the next iteration operation, the cipher key bits are shifted according to a predetermined shift schedule to provide a new set of permuted cipher key bits. The modified second half of the message block is then used with the new set of permuted cipher ket bits in a similar product block cipher operation, the result of which is used to modify the first half of the message block. The modified first half of the message block then replaces the modified second half of the message block which at the same time replaces the first half of the message block in preparation for the next iteration operation. During each of the remaining iteration operations of the enciphering process except the last, the cipher key bits are shifted according to the predetermined shift schedule, a modified half of the message block is remodified according to a product block cipher of the previously modified half of the message block and the resulting remodified half of a message block is effectively transposed with the previously modified half of the message block. During the last iteration operation, the cipher key bits are shifted a last time according to the shift schedule and a last remodification of a modified half of the message block is performed according to a product block cipher of the previously modified half of the message block but the resulting remodified half of the message block and the previously modified half of the message block are not transposed and now constitute the enciphered version of the original message block. Deciphering an enciphered message block is carried out by the same series of iteration operations under control of the same cipher key shifted during the iteration operations according to a predetermined shift schedule in a direction opposite to that in the enciphering process to reverse the enciphering process and undo every iteration that was carried out in the enciphering process to produce a resulting message block identical with the original message block.

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Kingston, NY, United States of America

William F Ehrsam