Link encryption 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 bit-by-bit basis when received from said communications line, comprising:
- means for receiving said plain text data from said communications line on a bit-by-bit basis;
means for generating a plurality of key bits for each bit 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 said plain text data with one of said plurality of key bits generated for the bit previous to each of said bits of plain text data, whereby a bit of enciphered data is produced corresponding to each of said bits of plain text data; and
means for transmitting each of said bits of enciphered data onto said communications line, whereby each of said bits of plain text data is replaced by the corresponding bit of reciphered data.
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Accused Products
Abstract
An apparatus for insertion in a communications line for providing both message integrity and message secrecy within a significant portion of existing communications networks. At the transmitter end, the apparatus receives messages from the communications line, enciphers them on a bit-by-bit basis and retransmits them onto the communications line. At the receiver end, the apparatus receives messages from the communications line, deciphers them on a bit-by-bit basis 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 responsive to data previously received and a unique key entered by the user. As a data bit 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 bits. 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.
170 Citations
26 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 bit-by-bit 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 bit-by-bit basis; means for generating a plurality of key bits for each bit 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 said plain text data with one of said plurality of key bits generated for the bit previous to each of said bits of plain text data, whereby a bit of enciphered data is produced corresponding to each of said bits of plain text data; and means for transmitting each of said bits of enciphered data onto said communications line, whereby each of said bits of plain text data is replaced by the corresponding bit of reciphered data. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. 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 bit-by-bit basis when received from said communications line, comprising:
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means for receiving said enciphered data from said communications line on a bit-by-bit basis; means for generating a plurality of key bits for each bit of said enciphered data received from said communications line; means for storing said plurality of key bits; means for exclusive ORing each bit of said enciphered data with one of said plurality of key bits generated for the bit previous to each of said bits of enciphered data, whereby a bit of plain text data is produced corresponding to each of said bits of enciphered data; and means for transmitting each of said bits of plain text data onto said communications line, whereby each of said bits of enciphered data is replaced by the corresponding bit of plain text data. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 22)
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18. 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 bit-by-bit 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 bit-by-bit basis, comprising:
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means for receiving a bit of said plain text data being transmitted in said first direction from said communications line; means for enciphering said bit of plain text data received from said communications line; means for transmitting said bit of enciphered data corresponding to said bit of plain text data being transmitted in said first direction onto said communications line whereby said bit of plain text data being transmitted in said first direction is replaced by said bit of enciphered data corresponding to said bit of plain text data being transmitted in said first direction; means for receiving a bit of said enciphered data being transmitted in said second direction from said communications line; means for deciphering said bit of enciphered data received from said communications line; and means for transmitting said bit of deciphered data corresponding to said bit of enciphered data being transmitted in said second direction onto said communications line whereby said bit of enciphered data being transmitted in said second direction is replaced by said bit of deciphered data corresponding to said bit of enciphered data being transmitted in said second direction. - View Dependent Claims (19, 20, 21)
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23. An apparatus for use in the transmission of digital data in enciphered form, wherein a sequence of plain text data is sequentially enciphered on a bit-by-bit basis, comprising:
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means for generating a plurality of key bits for each bit of said sequence of plain text data; means for storing said plurality of generated key bits; and means for exclusive ORing each bit of said plain text data sequence with one of said plurality of key bits generated for the bit previous to each of said bits of said plain text data sequence, whereby a bit of enciphered data is produced corresponding to each of said bits of said plain text data sequence. - View Dependent Claims (24)
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25. An apparatus for use in the transmission of digital data in enciphered form, wherein a sequence of enciphered data is sequentially deciphered on a bit-by-bit basis, comprising:
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means for generating a plurality of key bits for each bit of said sequence of enciphered data; means for storing said plurality of generated key bits; and means for exclusive ORing each bit of said enciphered data sequence with one of said plurality of key bits generated for the bit previous to each of said bits of said enciphered data sequence, whereby a bit of plain text data is produced corresponding to each of said bits of said enciphered data sequence. - View Dependent Claims (26)
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Specification