3798360 is referenced by 119 patents and cites 1 patents.

This specification discloses a system that provides multiple level encipherment of a block of data by means of a stepped block cipher process. A data stream consisting of digital information is segmented into blocks of dimension D, each block is enciphered by means of a block cipher cryptographic system operating under the control of a unique subscriber digital key. The cryptographic system develops a first cipher text of equal dimension as the block D. Then the cryptographic system is effectively shifted to accept a plurality of data bits from a second data block and a plurality of bits from the first cipher. The combination of block data bits and ciphertext data bits forms a composite block of dimension equal to the data block D. This combination is introduced to the cryptographic device for developing a second cipher text. The combined output of the second ciphertext and those information symbols from the first ciphertext which were not reintroduced to the cryptographic device are transmitted as a complete unit to a receiving station which will decipher the received multiple level cryptogram by an inverse process.The multiple level encipherment process is also utilized in a variant key embodiment which would encipher a data block D into a cipher C which is a function of a key control block consisting of a random combination binary digits that are continuously changing.In a further embodiment which utilizes multiple level encipherment, there is presented a method for providing secrecy in communications between a central processing unit and its data banks.

Title
Step code ciphering system
Application Number
05/158,174
Publication Number
3798360
Application Date
June 30, 1971
Publication Date
March 19, 1974
Inventor
Feistel Horst
Agent
Siber Victor
Assignee
International Business Machines Corporation
IPC
H04l 09/02
H04L 09/06
H04L 09/00
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