Method and apparatus for ciphering and deciphering messages

• US 4,145,568 A
• Filed: 10/06/1964
• Issued: 03/20/1979
• Est. Priority Date: 10/18/1963
• Status: Expired due to Term

• Current Assignee: Omnisec AG Trockenloostrasse
• Original Assignee: Gretag AG (Peach Property Group AG)
• Inventors: Ehrat, Kurt
• Primary Examiner(s): Birmiel, Howard A.
• Application Number:
  US05/401,795
• Time in Patent Office: 5,278 Days
• Field of Search: 178/22, 178/26, 179/1.5, 179/2.5, 179/1.5 R, 325/32, 325/33, 325/34, 325/35, 325/122
• US Class Current: 380/47
• CPC Class Codes: H04L 9/065 Encryption by serially and continuously modifying data stream elements, e.g. stream cipher systems, RC4, SEAL or A5/3
• CPC Class Codes: H04L 9/12 Transmitting and receiving encryption devices synchronised or initially set up in a particular manner

Abstract

Method and apparatus for ciphering and deciphering messages, wherein series of cipher pulses with an identical pulse distribution are generated by the transmitter and the receiver stations and said pulse distribution is determined by a secret basic code and a code which is derived from date and time.

Claims

1. A method of ciphering and deciphering messages comprising generating a series of cipher pulses, generating a series of basic code pulses, generating a series of additional code pulses representing date and time, mixing the code and date-time pulses to produce a series of pulses for controlling the generation of the cipher pulse, generating a series of pulses representing a message to be transmitted, mixing the cipher pulses with said message pulses and transmitting the ciphered message to a receiving station, generating a series of cipher pulses identical to and in synchronism with the control series of cipher pulses and mixing the identical series of cipher pulses with the ciphered message pulses to decipher the message.

2. A method according to claim 1 in which said additional date-time code pulses are generated in sequential groups, each group of pulses representing a different date-time combination.

3. A method according to claim 1 including generating a random series of pulses, mixing the random series of pulses with the control series of pulses, and transmitting the random series of pulses to the receiving station to control the generation of said identical series of cipher pulses so that both series of cipher pulses are identical and in synchronism.

4. A method of ciphering and deciphering messages comprising generating a series of basic code pulses, generating a series of additional code pulses representing date and time, mixing at least part of the series of basic code pulses with the series of additional date-time code pulses and storing the resulting series of mixed code pulses in a shift register, generating a series of pulses representing a message to be transmitted, controlling the read-out of said shift register by a counter which in turn controls the minimum period length of the resulting series of cipher pulses, mixing the message pulses with the cipher pulses read out of the shift register, and transmitting the ciphered message to a receiver, generating a series of cipher pulses identical to and in synchronism with the series of cipher pulses read out of the shift register, and mixing the identical series of cipher pulses with the received ciphered message pulses to decipher the message.

5. A method of ciphering and deciphering messages comprising generating a series of binary coded pulses representing date and time, generating a series of binary coded pulses representing a basic code, mixing the binary coded date-time and basic code series of pulses to produce a series of binary coded control pulses, generating a series of cipher pulses under control of the control pulses, generating a series of pulses representing a message to be transmitted, mixing the series of cipher pulses with the message pulses and transmitting the ciphered message pulses to a receiver, receiving the ciphered message pulses, generating a series of cipher pulses in an identical fashion to and in synchronism with the first mentioned series of cipher pulses, and mixing the identical series of cipher pulses with the received ciphered message pulses to decipher the message.

6. A method according to claim 5 in which the binary coded date-time series of pulses is generated by a quartz crystal controlled clock and a code converter, the former generating pulses representing the date and time and the latter converting the last mentioned pulses to binary form.

7. Apparatus for ciphering and deciphering messages comprising a cipher pulse generator for generating a series of cipher pulses, a code generator for generating a series of basic code pulses, a date-time generator for generating a series of additional code pulses representing date and time, a first mixer for mixing the basic code and additional date-time code pulses to produce a series of pulses to control the generation of the cipher pulses, a generator for generating a series of pulses representing a message to be transmitted, a second mixer for mixing the cipher pulses with said message pulses, and a receiver for receiving the transmitted ciphered message pulses including means to decipher said message comprising means operable in synchronism with said cipher pulse generator to generate a series of pulses identical to said series of control pulses and a third mixer for mixing said identical series of pulses with said ciphered message pulses to decipher said message.

8. Apparatus as claimed in claim 7 in which said date-time pulse generator generates sequential groups of pulses, each group representing a different time.

9. Apparatus as claimed in claim 7 including a random pulse generator for generating a random series of pulses, to store for storing said random series of pulses, means for mixing said random series of pulses with the basic code and additional date-time code series of pulses in said first mixer, and means for transmitting said random series of pulses to said receiver for controlling the generation of said identical series of cipher pulses so that both series of cipher pulses are identical and in synchronism.

13. Apparatus as claimed in claim 8 which said date-time pulse generator includes a quartz crystal controlled clock, said clock providing electrical pulses representing the date and time.

10. Apparatus for ciphering and deciphering messages comprising a cipher pulse generator for generating a series of cipher pulses, a code generator for generating a series of basic code pulses, a date-time generator for generating a series of additional code pulses representing time and date, said cipher pulses generator including a shift register, a counter and a feedback circuit connecting said shift register to said counter, a control unit for controlling the entry of at least part of the basic code series of pulses into said shift register, a first mixer for mixing said additional date-time code series of pulses with the basic code series of pulses stored in said shift register, said control unit placing the series of cipher pulses produced by said first mixer into storage in said shift register, a generator for generating a series of pulse representing a message to be transmitted, means for feeding said message pulses into said first mixer for mixing with the series of cipher pulses stored in the shift register, means for transmitting said ciphered message to a receiver means in said receiver operable in synchronism with the cipher pulse generator to generate a series of pulses identical to the series of cipher pulses stored in said shift register and a second mixer for mixing said identical series of cipher pulses with the received ciphered messages pulses to decipher the message.

11. Apparatus for ciphering and deciphering messages comprising a first generator for generating a series of binary coded pulses representing date and time, a second generator for generating a series of binary coded pulses representing a basic code, a first mixer for mixing the binary coded date-time and basic code series of pulses to produce a series of binary coded control pulses, a third generator settable by said control pulses to generate a series of cipher pulses, a fourth generator for generating a series of pulses representing a message to be transmitted, a second mixer for mixing the series of cipher pulses with said message pulses for transmission, a receiver for receiving the ciphered message pulses including fifth, sixth and seventh generators and a third mixer all identically operable to the first, second and third generators and said first mixer respectively to produce a series of cipher pulses identical to and in synchronism with the cipher pulse series generated by said third generator and a fourth mixer for mixing said identical series of cipher pulses with the received ciphered message pulses to decipher said message.

12. Apparatus as claimed in claim 11, in which said first generator includes a quartz crystal controlled clock and a binary code converter, said clock providing electrical pulses representing the date and time and said converter converting the last mentioned pulses to a binary coded series of pulses.

14. Apparatus for ciphering and deciphering messages comprising a cipher pulse generator for generating a series of cipher pulse, a code generator for generating a series of basic code pulses, a date-time generator for generating a series of additional code pulses representing a time and date, said cipher pulse generator including a shift register, a counter and a feedback circuit connecting said shift register to said counter, a control unit for controlling the entry of part of the basic code series of pulses into said shift register, a first mixer for mixing said additional date-time code series of pulses with the basic code series of pulses stored in said shift register, said control unit placing the series of mixed coded pulses produced by said first mixer into storage in said counter, said control unit controlling the entry of the other part of the basic code series of pulses into said shift register, means for mixing said additional date-time code series of pulses with said other part of the basic code series of pulses stored in said shift register, said control unit placing the series of cipher pulses produced by the means for mixing said other part of the basic code series and date-time code series of pulses into storage in said shift register, a generator for generating a series of pulses representing a message to be transmitted, means for feeding said message pulses into said first mixer for mixing with the series of cipher pulses stored in the shift register, means for transmitting said ciphered message to a receiver means in said receiver operable in synchronism with the cipher pulse generator to generate a series of pulses identical of the series of cipher pulses stored in said shift register and a second mixer for mixing said identical series of cipher pulses with the received ciphered message pulses to decipher the message.