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Encrypting Decrypting Communication Link

IP.com Disclosure Number: IPCOM000088222D
Original Publication Date: 1977-May-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 4 page(s) / 45K

Publishing Venue

IBM

Related People

Callahan, RW: AUTHOR

Abstract

A method is described for encrypting and decrypting digital data transmitted via a telephone, radio, satellite, fiber optic, laser beam, or some other type of communications system. Transmitted data is serially scrambled by hardware at the sending end and unscrambled by hardware at the receiving end in a manner that is virtually impossible to decipher. No secret code exists to be broken. Every user or group of users who agree to communicate have their own unique hardware.

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Encrypting Decrypting Communication Link

A method is described for encrypting and decrypting digital data transmitted via a telephone, radio, satellite, fiber optic, laser beam, or some other type of communications system. Transmitted data is serially scrambled by hardware at the sending end and unscrambled by hardware at the receiving end in a manner that is virtually impossible to decipher. No secret code exists to be broken.

Every user or group of users who agree to communicate have their own unique hardware.

Fig. 1 shows a rudimentary form of the technique. Each byte of data (data bits 0-7 and parity check bit P) is supplied to an encryptor 10 which includes an input data register 11, an output shift register 12 and register-to-register wiring 13, which serves to scramble the order of the bits supplied to the shift register 12. The data in shift register 12 is read out in a serial bit-by-bit manner and transmitted by means of a transmitter 14 and a communications link 15 to a receiver 16. Each byte of received data is supplied to a decryptor 17, which serves to unscramble the bits therein and restore them to their original order. Decryptor 17 includes an input shift register 18 into which the received bits are entered in a serial manner, an output data register 19 and register-to-register wiring 20, which matches the encryptor wiring 13 in the manner needed to unscramble the scrambled bits. Thus, the output data taken from the data register 19 at the receiving station is exactly the same as the original input data supplied to the data register 11 at the sending station.

Fig. 2 shows the sending or transmitting apparatus for a more sophisticated and desirable embodiment. In this case, data is manipulated in 16-byte blocks. Each block of data to be scrambled is entered into a 16-byte data register 21, and the data to be transmitted appears in an output shift register 22. The data in shift register 22 is read out in a serial bit-by-bit manner and transmitted serially by a transmitter 23 to the receiving station.

Figs. 3A -3E show examples of five different blocks which may be transmitted in succession by the transmitter 23. "ADR" denotes an address field in each block and "CC" denotes a control code field in each block. The remainder of each block is occupied by the 16 bytes of scrambled data. As indicated by these examples, the data portion of each block is subdivided into anywhere from two to four data groups. The larger groups (8A or 8B) are eight bytes in length and the smaller groups (4A, 4B, 4C or 4D) are four bytes in length. As will be seen, a different encryptor is used for each group in a block.

As shown in Fig. 2, there are six sets of encryptors, designated 4A, 4B, 4C, 4D, 8A and 8B. Each set includes four separate and independent encryptors. Thus, set 4A includes the encryptors 4A-1, 4A-2, 4A-3 and 4A-4. Each of these encryptors has an input data register and an output data register which are interconnected by scramb...