Polymorphic encryption method and system

• US 20070028088A1
• Filed: 08/01/2005
• Published: 02/01/2007
• Est. Priority Date: 08/01/2005
• Status: Abandoned Application

• Current Assignee: The Board of Trustees of the University of Arkansas (University of Arkansas System)
• Original Assignee: The Board of Trustees of the University of Arkansas (University of Arkansas System)
• Inventors: Bayrak, Coskun, Topaloglu, Umit
• Application Number:
  US11/194,169
• Publication Number:
  US 20070028088A1
• Time in Patent Office: Days
• US Class Current: 713/150
• CPC Class Codes: H04L 2463/062 applying encryption of the keys cryptographic mechanisms or cryptographic arrangements for key distribution using key encryption key H04L9/0822
• CPC Class Codes: H04L 63/0428 wherein the data content is protected, e.g. by encrypting or encapsulating the payload
• CPC Class Codes: H04L 9/0631 Substitution permutation network [SPN], i.e. cipher composed of a number of stages or rounds each involving linear and nonlinear transformations, e.g. AES algorithms
• CPC Class Codes: H04L 9/0662 with particular pseudorandom sequence generator
• CPC Class Codes: H04L 9/0825 using asymmetric-key encryption or public key infrastructure [PKI], e.g. key signature or public key certificates

Abstract

The invention is directed to a symmetric encoding and decoding architecture for a communication system that may be implemented using multiple encoding levels. By changing the number of levels used, the system may be adapted to the user'"'"'s speed and security requirements. Cryptoanalysis techniques attacking the encoding process may yield multiple meaningful messages, without the ability of the attacker to determine which message is the correct one. The encrypted messages may also be compressed according to an algorithm that is effective even for small message sizes, and an exclusive-OR (XOR) function may be applied to the result to thwart an attack by a party that knows the compression algorithm.

Claims

1. A method of encoding a message sent from a sender to a receiver, comprising the steps of:

(a) generating a first character set;

(b) generating a key comprising characters within the first character set;

(c) creating a sender assignment table using the key, the sender assignment table comprising a plurality of values corresponding to each character in the first character set, and each of the sender assignment table values comprised of characters from a second character set;

(d) substituting each character in a plaintext message comprised of the first character set with the corresponding sender assignment table value to create a ciphertext message;

(e) repeating said substitution step a number of times equal to a specified level number, each repetition being performed upon the ciphertext message resulting from the preceding substitution step; and

(f) passing the ciphertext message resulting from said repetition of said substitution step with the level number to a receiver.

2. The method of claim 1, further comprising the step of compressing the ciphertext message to result in a compressed ciphertext message.

3. The method of claim 2, wherein said compression step comprises the substitution of at least one string in the ciphertext message with an identifier.

4. The method of claim 2, further comprising the step of performing an exclusive-OR (XOR) operation between the compressed ciphertext message and the key.

5. The method of claim 1, wherein said key is generated using one of a random and pseudo-random number generator.

6. The method of claim 5, wherein said key is a string comprised of each of the characters of the first character set in one of a random and pseudo-random order.

7. The method of claim 1, further comprising the step of passing the key and the level number to a receiver with the ciphertext message.

8. The method of claim 7, further comprising the step of, in a first communication, passing the key to a receiver using a public-key encryption system.

9. The method of claim 8, further comprising the step of, in a second and all subsequent communications, encrypting the key in the same manner as the plaintext message before sending the key to the receiver.

10. The method of claim 9, further comprising the step of substituting the level number with the corresponding sender assignment table value for the character representing the level number to create a ciphertext level number, and passing the ciphertext level number to a receiver with the ciphertext message.

11. The method of claim 10, further comprising the steps of receiving the plaintext message from a first graphical user interface in communication with the sender, and displaying the plaintext message at a second graphical user interface in communication with the receiver.

12. The method of claim 1, further comprising the steps of:

(a) using the received key to create a receiver assignment table, the receiver assignment table comprising a plurality of values corresponding to each character in the first character set, and each of the receiver assignment table values comprised of characters from the second character set;

(b) substituting each character string in the ciphertext message corresponding to a receiver assignment table value with the corresponding character to create a resultant message; and

(c) repeating said substitution step a number of times equal to the specified level number, each repetition being performed upon the resultant message resulting from the preceding substitution step until a plaintext message is generated.

13. The method of claim 12, further comprising the step of decompressing the ciphertext message to result in a decompressed ciphertext message.

14. The method of claim 13, wherein said decompression step comprises the substitution of at least one identifier in the ciphertext message with a character string.

15. The method of claim 13, further comprising the step of performing an exclusive-OR (XOR) operation between the ciphertext message and the key prior to said decompression step.

16. A system for the transmission of encoded messages, comprising:

(a) a network operable to transmit messages;

(b) first and second communication sockets connected to said network wherein said first communication socket is operable to send a message over said network to said second communication socket;

(c) an encoding module in communication with said first communication socket, said encoding module comprising;

(i) a key generation module operable to generate a key;

(ii) an encoding assignment table generation module operable to generate an assignment table using the key, wherein the assignment table comprises each possible character in a plaintext message and a corresponding substitution character set for each such character; and

(iii) an encoding substitution module operable to generate a ciphertext message from a plaintext message by substituting for each character in a plaintext message the corresponding substitution character set for each such character, and repeating such operation on the resulting ciphertext message a number of times equal to a level number;

(d) a decoding module in communication with said second communication socket, said decoding module comprising;

(i) a decoding assignment table generation module operable to generate an assignment table using a key, wherein the assignment table comprises each possible character in a plaintext message and a corresponding substitution character set for each such character; and

(ii) a decoding substitution module operable to generate a plaintext message from a ciphertext message by substituting for each substitution character set in a ciphertext message the corresponding character, and repeating such operation on the resulting message a number of times equal to a level number, resulting in a plaintext message;

(e) a first user interface in communication with said encoding module wherein said first user interface is operable to receive as input a plaintext message and a level number and communicate said plaintext message and said level number to said encoding module; and

(f) a second user interface in communication with said decoding module wherein said second user interface is operable to display as output a plaintext message received from said decoding module.

17. The system of claim 16, wherein said encoding module further comprises a compression module operable to receive the ciphertext message and output a compressed ciphertext message.

18. The system of claim 17, wherein said compression module is operable to substitute at least one string in the ciphertext message with an identifier.

19. The system of claim 17, wherein said encoding module further comprises an exclusive-OR (XOR) module operable to perform an XOR function with respect to the compressed ciphertext message and the key.

20. The system of claim 17, wherein said decoding module further comprises a decompression module operable to receive the compressed ciphertext message and output a decompressed ciphertext message.

21. The system of claim 20, wherein said decompression module is operable to substitute at least one identifier in the ciphertext message with a string.

22. The system of claim 21, wherein said decoding module further comprises an exclusive-OR (XOR) module operable to perform an XOR function with respect to the compressed ciphertext message and the key.

23. The system of claim 16, wherein said key generation module comprises one of a random and pseudo-random number generator.

24. The system of claim 16, wherein each said substitution character set is comprised of a first set of characters, and said key generation module is operable to create a key of a length equal to the number of characters in said first character set.

25. The system of claim 16, wherein said first communication socket is further operable to transmit said level number and said key over said network to said second communication socket.

26. The system of claim 16, wherein said encoding substitution module is operable to encode said key by substituting for each character in said key the corresponding substitution character set for each such character, and repeating such operation a number of times equal to a level number.

27. The system of claim 16, wherein said decoding substitution module is operable to decode said key by matching substitution character sets from the key and substituting the corresponding character, and repeating such operation on a resulting intermediate key string a number of times equal to a level number.

28. The system of claim 16, further comprising a public key encryption module in communication with said first communication socket, said public key encryption module operable to encode a key according to a public key encryption routine.

29. The system of claim 16, wherein said second communication socket is further operable to send a message over said network to said second communication socket, said second user interface is further operable to receive as input said plaintext message and said level number and communicate said plaintext message and said level number to said second encoding module, said first user interface is further operable to display as output the plaintext message received from said second decoding module, and further comprising:

(a) a second encoding module in communication with said second communication socket, said second encoding module comprising;

(i) a second key generation module operable to generate a key;

(ii) a second encoding assignment table generation module operable to generate an assignment table using the key, wherein the assignment table comprises each possible character in a plaintext message and a corresponding substitution character set for each such character; and

(iii) a second encoding substitution module operable to generate a ciphertext message from a plaintext message by substituting for each character in a plaintext message the corresponding substitution character set for each such character, and repeating such operation on the resulting ciphertext message a number of times equal to a level number; and

(b) a second decoding module in communication with said first communication socket, said second decoding module comprising;

(i) a second decoding assignment table generation module operable to generate an assignment table using a key, wherein the assignment table comprises each possible character in a plaintext message and a corresponding substitution character set for each such character; and

(ii) a second decoding substitution module operable to generate a plaintext message from a ciphertext message by substituting for each substitution character set in a ciphertext message the corresponding character, and repeating such operation on the resulting message a number of times equal to a level number, resulting in a plaintext message.

30. A method of communicating between a first and second node using encoded messages, comprising the steps of:

(a) receiving a plaintext message and a level number at the first node;

(b) generating a key at the first node;

(c) creating a first assignment table at the first node using the key, wherein the first assignment table comprises an assignment table value corresponding to each possible character in the plaintext message;

(d) substituting each character in the plaintext message with the corresponding assignment table value to create a ciphertext message, and repeating said substitution step a number of times equal to the level number, each repetition being performed upon the ciphertext message resulting from the preceding substitution step;

(e) substituting a character representing the level number with the corresponding assignment table value to create a ciphertext level number;

(f) encrypting the key with a public key encryption technique;

(g) passing the public-key encrypted key to the second node; and

(h) passing the ciphertext message and ciphertext level number to the second node.

31. The method of claim 30, further comprising the step of compressing the ciphertext message to result in a compressed ciphertext message.

32. The method of claim 31, wherein said compression step comprises the substitution of at least one string in the ciphertext message with an identifier.

33. The method of claim 31, further comprising the step of performing an exclusive-OR (XOR) operation between the compressed ciphertext message and the key.

34. The method of claim 30, further comprising the steps of:

(a) receiving the public-key encrypted key and the encrypted ciphertext message and ciphertext level number at the second node;

(b) decrypting the public-key encrypted key using the public-key encryption technique;

(c) creating a second assignment table at the second node using the key, wherein the second assignment table comprises an assignment table value corresponding to each possible character in the plaintext message;

(d) substituting the ciphertext level number with the character corresponding to its assignment table value to generate the level number;

(e) substituting each character string in the ciphertext message corresponding to an assignment table value with the corresponding character to create a resultant message, and repeating said substitution step a number of times equal to the level number, each repetition being performed upon the resultant message resulting from the preceding substitution step until a plaintext message is generated.

35. The method of claim 34, further comprising the step of decompressing the ciphertext message to result in a decompressed ciphertext message.

36. The method of claim 35, wherein said decompression step comprises the substitution of at least one identifier in the ciphertext message with a string.

37. The method of claim 35, further comprising the step of performing an exclusive-OR (XOR) operation between the compressed ciphertext message and the key prior to said decompression step.

38. The method of claim 34, further comprising the steps of:

(a) receiving a second plaintext message at the first node;

(b) substituting each character in the second plaintext message with the corresponding assignment table value to create a second ciphertext message, and repeating said substitution step a number of times equal to the level number, each repetition being performed upon the second ciphertext message resulting from the preceding substitution step;

(c) substituting each character in the key with the corresponding assignment table value to create a ciphertext key; and

(g) passing the ciphertext message, ciphertext level number, and ciphertext key to the second node.