Byte stream selective encryption/decryption device
First Claim
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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Accused Products
Abstract
An apparatus for insertion in a communications line for providing message secrecy within a significant portion of existing communications networks. At the transmitter end, the apparatus receives messages from the communications line, enciphers them and retransmits them onto the communications line. At the receiver end, the apparatus receives messages from the communications line, deciphers them and retransmits them onto the communications line. The apparatus contains both a transmitter and receiver and is capable of full duplex operation in a bidirectional communications line. According to the invention, data is enciphered by combining the data received with the output of an algorithm, the algorithm output being dependent on the data previously enciphered and a unique key entered by the user. As data is received it is combined with the output of the algorithm, transmitted and using cipher feedback techniques fed back as an input to the algorithm to be used to encipher subsequently received data. Data is deciphered using equivalent elements as used for enciphering, the basic difference in the apparatus operation being the point from which data fed back into the algorithm is taken. The apparatus operates on a byte-by-byte basis, and contains provisions for responding to control characters and ignoring messages intended for a different apparatus.
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Citations
49 Claims
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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:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40)
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21. An apparatus for providing data communications security in point-to-point and multipoint communications networks, wherein enciphered data on a communications line is deciphered on a byte-by-byte basis when received from said communications line, comprising:
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means for receiving said enciphered data from said communications line on a byte-by-byte basis; means for generating a plurality of key bits for each byte of said enciphered 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 enciphered data with one of said plurality of key bits generated for the byte previous to each of said bytes of enciphered data, whereby a byte of plain text data is produced corresponding to each of said bytes of enciphered data; and means for transmitting each of said bytes of plain text data onto said communications line, whereby each of said bytes of enciphered data is replaced by the corresponding byte of plain text data. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29)
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41. An apparatus for insertion in a bidirectional communications line for providing full duplex data communications security in point-to-point and multipoint communications networks, wherein plain text data being transmitted on said communications line in a first direction is received by said apparatus, enciphered, and transmitted back onto said communications line in said first direction on a byte-by-byte basis, and enciphered data being transmitted on said communications line in a second direction is received by said apparatus, deciphered and transmitted back onto said communications line in said second direction on a byte-by-byte basis, comprising:
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means for receiving said plain text data being transmitted in said first direction from said communications line on a byte-by-byte basis; first means for generating a first plurality of key bits for each byte of said plain text data received from said communications line; second means for storing said first plurality of key bits; third means for exclusive ORing each bit of each received byte of said plain text data with one of said first plurality of key bits generated for the byte of data received previous to each of said bytes of plain text data received, whereby a byte of enciphered data is produced corresponding to each of said received bytes of plain text data; means for transmitting each of said produced bytes of enciphered data onto said communications line in said first direction, whereby each of said received bytes of plain text data being transmitted in said first direction is replaced by the corresponding produced byte of enciphered data; means for receiving said enciphered data being transmitted in said second direction from said communications line on a byte-by-byte basis; fourth means for generating a second plurality of key bits for each byte of said enciphered data received from said communications line; fifth means for storing said second plurality of key bits; sixth means for exclusive ORing each bit of each received byte of said enciphered data with one of said second plurality of key bits generated for the byte of data received previous to each of said bytes of enciphered data received, whereby a byte of plain text data is produced corresponding to each of said received bytes of enciphered data; and means for transmitting each of said produced bytes of plain text data onto said communications line in said second direction, whereby each of said received bytes of enciphered data being transmitted in said second direction is replaced by the corresponding produced byte of plain text data. - View Dependent Claims (42, 43)
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44. An apparatus for use in transmitting enciphered digital data, wherein a sequence of bytes of plain text data is sequentially enciphered on a byte-by-byte basis, comprising:
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means for generating a plurality of key bits for each of said bytes of plain text data; and means for exclusive ORing each bit of each of said bytes of plain text data with one of said plurality of key bits generated for the byte of plain text data 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. - View Dependent Claims (45, 46)
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47. An apparatus for use in transmitting enciphered digital data, wherein a sequence of bytes of enciphered data is sequentially deciphered on a byte-by-byte basis, comprising:
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means for generating a plurality of key bits for each of said bytes of enciphered data; and means for exclusive ORing each bit of each of said bytes of enciphered data with one of said plurality of key bits generated for the byte of enciphered data previous to each of said bytes of enciphered data, whereby a byte of plain text data is produced corresponding to each of said bytes of enciphered data. - View Dependent Claims (48, 49)
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Specification