International Business Machines Corporation

Paul N Prentice

Carl H Meyer

Walter L Tuchman

Stephen M Matyas

William F Ehrsam

John L Smith

Robert Lowell Powers

Robert C Elander

Jonathan Oseas

Richard E Lennon

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

In a data communication network providing communication security for communication sessions between a first station and a second station where each station has cryptographic apparatus provided with an operational key which should be common to both stations for cryptographic operations, an operational key verification arrangement is provided in which a first number provided at the first station is operated upon in accordance with the first station operational key to obtain cryptographic data for transmission to the second station, requiring the second station to perform an operation on the first station cryptographic data in accordance with the second station operational key to obtain cryptographic data for transmission back to the first station and performing an operation at the first station in accordance with the first number and the second station cryptographic data to verify that the second station is the source of second station cryptographic data only if the operational keys are identical.

Cryptographic verification of operational keys used in communication

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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Hyde Park, NY, United States of America

Paul N Prentice