Abstract The specification discloses a digital cryptographic system operating under a digital coding scheme having forbidden control characters with common bit characteristics. In the encoding mode, clear digital data and randomized digital data are stored and selected bits of the clear and randomized digital data are modulo-2 added. The added bits are then examined to determine whether or not the bits have the common bit characteristics of the forbidden control characters. If so, the selected bits of the stored clear digital data are varied to prevent the subsequent generation of forbidden control characters in the encoded data. The clear digital data and randomized digital data are then modulo-2 added to generate encoded data. The present system is compatible with eight-level digital codes and the system includes parity bit checking techniques to ensure accuracy of operation. The present system may be operated as either an On-line or Offline system and may be utilized to provide security of digital transmission between teleprinters or between a teleprinter and a digital computer or the like.
Inventors
👤 Barrie O Morgan
👤 Kenneth M Branscome
👤 George E Goode
👤 John Q Atchley
Bibliographic Details
Application Number—
JurisdictionUS
Data Sourcegoogle_patents
Last Synchronized2026-10-23 22:48
CPC Classifications
H; H04; H04L; H04L9/00; H04L9/36
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
146 words
A digital cryptographic system operable in off-line and online modes comprising: means for generating clear text digital data including clear digital words, first and second storage registers for storing said clear digital words, input and output synchronizers operable to control said storage registers, means for generating randomized digital data, encoding circuitry for receiving said clear digital words and said randomized digital data for generating encoded digital data, off-line mode switch means for connecting said system such that said clear digital words are stored in said first storage register under the control of said input synchronizer prior to being shifted to said encoding circuitry, and on-line mode switch means for connecting said system such that said clear digital words are sequentially stored in said first and second storage registers under the sequential control of said input and output synchronizers prior to being shifted to said encoding circuitry.
Claim 2
Dependent Claim
146 words
A digital cryptographic system operable in off-line and online modes comprising: means for generating clear text digital data including clear digital words, first and second storage registers for storing said clear digital words, input and output synchronizers operable to control said storage registers, means for generating randomized digital data, encoding circuitry for receiving said clear digital words and said randomized digital data for generating encoded digital data, off-line mode switch means for connecting said system such that said clear digital words are stored in said first storage register under the control of said input synchronizer prior to being shifted to said encoding circuitry, and on-line mode switch means for connecting said system such that said clear digital words are sequentially stored in said first and second storage registers under the sequential control of said input and output synchronizers prior to being shifted to said encoding circuitry.
Claim 3
Dependent Claim
49 words
The cryptographic system of claim 1 wherein said encoding circuitry comprises: first and second modulo-2 adders, said first adder receiving said clear digital words and randomized digital data in said off-line mode, and said second adder receiving said clear digital words and randomized digital data in said on-line mode.
Claim 4
Dependent Claim
34 words
The cryptographic system of claim 2 and further comprising: multivibrator means, and means responsive to said off-line mode switch for connecting said multivibrator means between said first storage register and said first modulo-2 adder.