Encryption system based on chaos theory

• US 5,048,086 A
• Filed: 07/16/1990
• Issued: 09/10/1991
• Est. Priority Date: 07/16/1990
• Status: Expired due to Term

• Current Assignee: Hughes Electronics Corporation (AT&T, Inc.)
• Original Assignee: Hughes Aircraft Company (Rtx Corporation)
• Inventors: Reed, Dana A., Bianco, Mark E.
• Primary Examiner(s): Gregory, Bernarr E.
• Application Number:
  US07/553,030
• Time in Patent Office: 421 Days
• Field of Search: 364/200, 364/900, 380/6, 380/9, 380/28, 380/43, 380/46, 380/49, 380/50, 380/59, 380/29-30
• US Class Current: 380/28
• CPC Class Codes: H04L 27/001 using chaotic signals for secret or secure communication H04L9/001
• CPC Class Codes: H04L 9/001 using chaotic signals
• CPC Class Codes: H04L 9/0662 with particular pseudorandom sequence generator

Abstract

An encryption system and method based on the mathematics of Chaos theory, which provides protection of data from unauthorized modification and use during its storage and transmission. At its core are nonlinear equations which exhibits random, noise-like properties, given certain parameter values. When iterated, a periodic sequence is produced with an extremely long cycle length. A domain transformation process is then used to convert the floating-point iterates into binary form for summation with the digital data to be protected. The result is an encrypted message that cannot be modified, replaced, or understood by anyone other than the intended party. The use of Chaos theory in combination with the domain transformation process results in an easily implemented cryptographic system with extremely robust cryptographic properties. The concepts of the present invention also lend themselves well to either hardware or software implementations. The cryptographic system of the present invention may be employed to encrypt and decrypt sensitive information, to authenticate data and video links, or similar applications. It can also be used to provide a simple hash function for the secure storage of passwords in a computer system. Its simplicity, requiring only floating-point operations at its core, allows a lower cost and higher performance product with cryptographic security equivalent to conventional cryptographic systems.

Claims

1. A cryptographic system comprising:

a random number generator;

a memory for storing one or more cryptographic keys;

an arithmetic means coupled to the random number generator and memory for iterating a predetermined logistic difference equation having the form x_n+1 =μ

x_n (1-x_n), where μ

is a cryptographic key, x_n is a random number generated by the random number generator, and x_n+1 is an iterated result generated by succesively calculating x_n+1 in the above equation a selected number of successive times. to thereby generate a sequence of encrypting iterates, and for converting the sequence of encrypting iterates into binary form;

adder means coupled to the arithmetic means for summing the encrypting iterates with digital data to thereby generate encrypted data; and

controller means for controlling the operation of and transfer of data between the random number generator, the memory, the arithmetic means, and the adder means.

2. The system of claim 1 wherein the arithmetic means comprises:

means for adjusting the mathematical precision of the random number generator to adjust the sequence of encrypting iterates.

3. The system of claim 1 wherein the arithmetic means comprises:

means for feeding back the encrypted data;

means for summing the encrypted data with the sequence of encrypting iterates to generate a second sequence of encrypting iterates;

means for delaying the second sequence of encrypting iterates for a selected time period; and

means for summing the delayed second sequence of encrypting iterates with digital data to be encrypted to generate additional encrypted data.

4. A method of encrypting data comprising the steps of:

calculating a value to be used as a random starting point;

generating an intitial state of a predetermined logistic difference equation having the form x_n+1 =μ

x_n (1-x_n), where μ

is a cryptographic key, x_n is the random starting point, and x_n+1 is an iterated result;

iterating the logistic differnce equation by using successive x_n+1 values to x_n and repeating the calculation a selected number of times, the random value x_n and the key value μ

having a selected mathematical precision, for a selected number of iterations to thereby generate a sequence of encrypting iterates;

converting the encrypting iterates into binary form; and

summing the encrypting iterates in binary form with digital data to generate encrypted data.

5. The method of claim 4 wherein the step of iterating the logistic difference equation further comprises the step of:

reiterating the logistic difference equation until the encrypting iterates are within a selected range.

6. The method of claim 4 wherein the step of iterating the logistic difference equation further comprises selecting a desired floating point mathematical precision for the iterating process to alter the sequence of encrypting iterates.

7. The method of claim 4 wherein the step of iterating the logistic difference equation further comprises the steps of:

summing previously encrypted data with new encrypting iterates in binary form to generate a second set of encrypting iterates in binary form;

delaying the second set of encrypting iterates in binary form for a selected time period; and

summing the delayed second set of encrypting iterates in binary form with digital data to be encrypted to generate additional encrypted data.

8. A method of decrypting data encrypted in accordance with the method of claim 4, said method comprising the steps of:

receiving encrypted data that is to be decrypted;

receiving a value used as a random starting point;

calculating an initial state of the logistic difference equation having the form x_n+1 =μ

x_n (1-x_n), where μ

is a cryptographic key, x_n is the random starting point, and x_n+1 is an iterated result;

iterating the logistic difference equation by assigning successive finite values to x_n and repeating the calculation a selected number of times to thereby generate a sequence of encrypting iterates;

converting the iterated values into binary form; and

summing the iterated values in binary form with the encrypted data to be decrypted to generate decrypted data.

9. The method of claim 8 wherein the step of iterating the logistic difference equation further comprises the step of:

reiterating the the logistic difference equation until the iterated results are within a selected range.

10. The method of claim 8 wherein the step of iterating the logistic difference equation further comprises the steps of:

summing the encrypted data with the sequence of decrypting iterates in binary form to generate a second set of decrypting iterates in binary form;

delaying the second set of decrypting iterates in binary form for a selected time period; and

summing the delayed second set of decrypting iterates in binary form with encrypted data to be decrypted to generate additional decrypted data.

11. A cryptographic system comprising:

random starting point generator means for generating a random starting point;

a memory for storing at least one cryptographic key;

arithmetic logic unit and arithmetic logic unit controller means coupled to the generator means and memory for iterating a predetermined logistic difference equation having the form x_n+1 =μ

x_n (1-x_n), where μ

is a cryptographic key, x_n is the random starting point, and x_n+1 is an iterated result, using the random starting point and a cryptographic key, for generating a sequence of iterates, and for converting the sequence of iterates into binary form;

adder means coupled to the arithmetic logic unit and arithmetic logic unit controller means for summing the iterates in binary form with digital data to generate encrypted data; and

sequencer means for controlling the operation of and transfer of data between the random starting point generator means, the memory, the arithmetic logic unit and arithmetic logic unit controller means.

12. The system of claim 11 wherein the arithmetic logic unit and arithmetic logic unit controller means comprises:

means for adjusting the mathematical floating point precision of the arithmetic logic unit to adjust the sequence of encrypting iterates.

13. The system of claim 11 wherein the arithmetic logic unit and arithmetic logic unit controller means comprises:

means for summing previously encrypted data with new encrypting iterates in binary form to generate a second set of encrypting iterates in binary form;

means for delaying the second set of encrypting iterates in binary form for a selected time period; and

means for summing the delayed second set of encrypting iterates in binary form with data to be encrypted to generate encrypted data.

14. The system of claim 11 wherein the arithmetic logic unit and arithmetic logic unit controller means comprises:

means for iterating the logistic difference equation and converting the result into binary form a selected number of times; and

means for summing the encrypting iterates in binary form with digital data to be encrypted to generate encrypted data.