Cryptography – Communication system using cryptography – Data stream/substitution enciphering
Patent
1994-02-08
1995-09-19
Cain, David C.
Cryptography
Communication system using cryptography
Data stream/substitution enciphering
380 28, 380 49, 380 29, 380 46, H04L 900
Patent
active
054523583
ABSTRACT:
An apparatus and method for improving the security of an electronic codebook encryption scheme comprises a transmitter unit for encoding or encrypting data and a separate authorized receiver for decoding or decrypting data. Both the transmitter and receiver share a common secret key that has been communicated through a separate channel.
The transmitter includes a Mapping Table (MTable) that comprises a table of functions, where a first series of incrementally numbered expressions are equated with a second series of randomly generated numbers. The plaintext is input into the transmitter and applied to the MTable to provide ciphertext. The PN generator supplies a unique random sequence of binary digits. The ciphertext byte and random number byte associated with each byte of plaintext data are exchanged to change the relationships within the MTable.
An Inverse Mapping Table (IMTable) is included in the receiver and is created by reversing the relationships between the sequential numbers and the mapping numbers in the MTable. From the encrypted communication, the ciphertext is separated and the respective functions for each ciphertext byte and random number byte are again exchanged, and the associated plaintext byte and random number byte are further exchanged to produce an MTable identical to that of the transmitter and unencrypted plaintext data identical to that originally encoded.
REFERENCES:
patent: 4233577 (1982-03-01), Brandstrom
patent: 4890324 (1989-12-01), Jansen
patent: 5351299 (1994-09-01), Matsuzaki et al.
Bidzos, D. James and Kaliski Jr., Burt S., "An Overview of Cryptography", Lan Times Feb., 1990.
Blahut, Richard E., "Digital Transmission of Information", Chapter 12.6, first para., Addison-Wesley Publishing Company, Jul. 9, 1993.
Blahut, Richard E., "Digital Transmission of Information", Chapter 12.7, Addison-Wesley Publishing Company, Jul. 9, 1993.
Sklar, Bernard, "Digital Communications: Fundamentals and Applications", Chapter 12.4 introduction, p. 694, Prentice Hall Publishers, 1988.
Kaliski, Burt, "Packet Encryption" RSA Laboratories, Slides 1,3,5,7,9,11,13,15,17, Jan. 22, 1992.
Chu Ke-Chiang
Normile James O.
Apple Computer Inc.
Cain David C.
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