Integer encryptor

• US 4,972,474 A
• Filed: 05/01/1989
• Issued: 11/20/1990
• Est. Priority Date: 05/01/1989
• Status: Expired due to Term

• Current Assignee: SafeNet Incorporated (Thales SA)
• Original Assignee: Cylink Corp. (Thales SA)
• Inventors: Sabin, Michael J.
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): CAIN, DAVID C
• Application Number:
  US07/345,803
• Time in Patent Office: 568 Days
• Field of Search: 380/28, 380/43, 380/49, 380/46
• US Class Current: 380/28
• CPC Class Codes: H04L 9/0662 with particular pseudorandom sequence generator

Abstract

A integer encryptor and decryptor, with the integer encryptor comprising a pseudorandom source, a discrete-time source, guard-band means, and adding means. The pseudorandom source generates a random-data signal. The random-data signal is an integer that lies within a first-bounded range. The discrete-time source generates the input-data signal. The guard-band means is coupled to the discrete-time source. In response to the input-data signal, the guard-band means generates an output-data signal. For a second-limit number the guard-band means limits the output-data signal to lie within a second-bounded range. The second-limit number is less than the first-limit number. The modulo-adding means is coupled to the pseudorandom source and the guard-band means. The modulo-adding means repetitively adds the output-data signal with the random-data signal and a third-limit number and generates an encrypted-data signal. The present invention also includes an integer decryptor having a pseudorandom source and modulo-adding means. The pseudorandom source generates a negative-random-data signal. The negative-random-data signal is the negative of the random-data signal generated at the integer encryptor. A communications channel outputs a channel signal, with the channel signal being a sum of the encrypted-data signal and an error signal. Modulo-adding means is coupled to the communications channel. The modulo-adding means repetitively adds the negative-random-data signal, the channel signal, and a fourth-limit number, and generates a receiver-output-data signal.

Claims

1. An integer encryptor for encrypting an input-data signal comprising:

a pseudorandom source for generating, at each time instant, t_i, a random-data signal, d_i, with the random-data signal having b-bits, with b≧

2, and for a first-limit number, B, with the random-data signal lying within a first-bounded range, -B≦

d_i <

B;

a discrete-time source for outputting, at each time instant, t_i, the input-data signal, s_i ;

guard-band means coupled to said discrete-time source and responsive to the input-data signal, s_i, for generating an output-data signal, x_i, wherein for a second-limit number, A, the output-data signal lies within a second-bounded range, -A≦

x_i ≦

A, with the second-limit number less than the first-limit number, A<

B; and

means coupled to said pseudorandom source and said guard-band means for repetitively adding the output-data signal with the random-data signal and a third-limit number, K_i, for generating an encrypted-data signal, c_i, according to a relationship c_i =x_i +d_i +2K_i B, with the third-limit number, K_i, being an integer that results in the encrypted-data signal lying within the range -B≦

c_i <

B.

2. An apparatus for decrypting an encrypted-data signal comprising:

a pseudorandom source for generating, at each time instant, t_i, a negative-random-data signal, -d_i, with the negative-random-data signal having b-bits, with b≧

2, with the negative-random-data signal being the negative of a random-data signal generated at an integer encryptor for encrypting the encrypted-data signal, c_i, respectively;

a communications channel for outputting, at each time instant, t_i, a channel signal, y_i, with the channel signal being a sum of the encrypted-data signal, c_i, and an error signal, e_i ; and

means coupled to said communications channel for repetitively adding the negative-random-data signal, -d_i, the channel signal, y_i, and a fourth-limit number, L_i, for generating a receiver-output-data signal, z_i, according to a relationship z_i =y_i +(-d_i) +2L_i B, and for a first-limit number, B, with the fourth-limit number, L_i, being an integer that results in the receiver-output-data signal lying within an output-bounded range, wherein -B≦

z_i <

B.

3. The apparatus as set forth in claim 2 wherein said pseudorandom-sequence source includes means for adjusting the time relationship of the generation of the negative-random-data signal at said decrypting apparatus with the random-data signal at said encryption apparatus.

4. An apparatus for encrypting an input-data signal comprising:

a pseudorandom source for generating a random-data signal;

a discrete-time source for outputting the input-data signal;

guard-band means coupled to said discrete-time source and responsive to the input-data signal for generating an output-data signal wherein a magnitude of an amplitude of the output-data signal is less than a magnitude of an amplitude of the random-data signal; and

means coupled to said pseudorandom source and said guard-band means for repetitively adding the output-data signal with the random-data signal and a third-limit number, for generating an encrypted-data signal, with the third-limit number being an integer that results in the encrypted-data signal lying within a first-bounded range.

5. An apparatus for decrypting an encrypted-data signal comprising:

a pseudorandom source for generating a negative-random-data signal;

a communications channel for outputting a channel signal with the channel signal being the sum of the encrypted-data signal and an error signal; and

means coupled to said communications channel for repetitively adding the negative-random-data signal, the channel signal, and a fourth-limit number, for generating a receiver-output-data signal, and with the fourth-limit number being an integer that results in the receiver-output-data signal lying within an output-bounded range.

6. The apparatus as set forth in claim 5 wherein said pseudorandom-sequence source includes means for adjusting the time relationship of the generation of the negative-random-data signal at said decrypting apparatus with the random-data signal at an encryption apparatus.

7. A method using a first processor for encrypting an input-data signal for transmission through a noisy communications channel, comprising the steps, using said first processor, of:

generating, at each time instant, t_i, a random-data signal, d.sub. i, and for a first-limit number, B, with the random-data signal lying within a first-bounded range, -B≦

d_i

generating, at each time instant, t_i, the input-data signal, s_i ;

generating from the input-data signal, s_i, an output-data signal, x_i, wherein for a second-limit number, A, the output-data signal lies within a second-bounded range, =A≦

x_i ≦

A, with the second-limit number less than the first-limit number, A<

B; and

repetitively adding, with the first processor, the output-data signal with the random-data signal and a third-limit number, K_i, for generating an encrypted-data signal, c_i, according to a relationship c_i =x_i +d_i +2K_i B, with the third-limit number, Ki, being an integer that results in the encrypted-data signal lying within the range -B≦

c_i <

B.

8. A method using a second processor for decrypting an encrypted-data signal, comprising the steps, using said second processor, of:

receiving, from a communications channel, a channel signal, y_i, with the channel signal being a sum of the encrypted-data signal, c_i, and an error signal, e_i ;

generating, at each time instant, t_i, a

negative-random-data signal, -d_i, with the negative-random-data signal being a negative of a random-data signal generated at an integer encryptor for encrypting the encrypted-data signal, c_i, respectively; and

repetitively adding the negative-random-data signal, -d_i, the channel signal, y_i, and a fourth-limit number, L_i, for generating a receiver-output-data signal, z_i, according to a relationship z_i =y_i +(-d_i)+2L_i B, and for a first-limit number, B, with the fourth-limit number, L_i, being an integer that results in the receiver-output-data signal lying within an output-bounded range, wherein -B≦

z_i <

B.