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 tenchiques 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 Synchronized2026-10-27 18:28
CPC Classifications
H; H04; H04L; H04L9/00; H04L9/36
Claims Analysis
Total Claims: 2
Claim 1
Independent Claim
147 words
An on-line digital cryptographic system comprising: means for receiving clear digital words from an input data terminal, a first register connected to said means for storing each clear digital word, circuitry for detecting the clear digital words stored in said register and for changing the stored digital words upon the detection of a forbidden digital character, a second register for receiving in parallel the stored clear digital words from said first register, output synchronizer means for applying a shift pulse to said second register to shift the stored clear digital words out of said second register, a modulo-2 adder for receiving the clear digital words from said second register, means for applying a randomized digital key stream to said adder in order to encipher the clear digital words, and means for transmitting said enciphered digital words on a substantially real time basis to a remote decoding station.
Claim 2
Dependent Claim
147 words
An on-line digital cryptographic system comprising: means for receiving clear digital words from an input data terminal, a first register connected to said means for storing each clear digital word, circuitry for detecting the clear digital words stored in said register and for changing the stored digital words upon the detection of a forbidden digital character, a second register for receiving in parallel the stored clear digital words from said first register, output synchronizer means for applying a shift pulse to said second register to shift the stored clear digital words out of said second register, a modulo-2 adder for receiving the clear digital words from said second register, means for applying a randomized digital key stream to said adder in order to encipher the clear digital words, and means for transmitting said enciphered digital words on a substantially real time basis to a remote decoding station.