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Byte stream selective encryption/decryption device

  • US 4,172,213 A
  • Filed: 11/17/1977
  • Issued: 10/23/1979
  • Est. Priority Date: 11/17/1977
  • Status: Expired due to Term
First Claim
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1. An apparatus for providing data communications security in point-to-point and multipoint communications networks, wherein plain text data on a communications line is enciphered on a byte-by-byte basis when received from said communications line, comprising:

  • means for receiving said plain text data from said communications line on a byte-by-byte basis;

    means for generating a plurality of key bits for each byte of said plain text data received from said communications line;

    means for storing said plurality of key bits;

    means for exclusive ORing each bit of each byte of said plain text data with one of said plurality of key bits generated for the byte previous to each of said bytes of plain text data, whereby a byte of enciphered data is produced corresponding to each of said bytes of plain text data; and

    means for transmitting each of said bytes of enciphered data onto said communications line, whereby each of said bytes of plain text data is replaced by the corresponding byte of enciphered data.

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