Bandwidth efficient method and system for obscuring the existence of encryption in a communications channel

Abstract

A system, method, and network interface obscures the existence of data encryption in a communication network is provided. A set of characters is generated by using a set of encryption keys as an input to a pseudo-random function. Each character corresponds to an index value. The encrypted data is divided into a plurality of parts. Each part is sectioned into a plurality of groups. Each group of the plurality of groups is encoded by mapping the group to a character in the set of characters according to its corresponding index value. The mapped characters are transmitted through the communication network.

What is claimed is: 
     
         1 . A non-transitory processor-readable storage medium storing instructions for execution by a processor to encode an encrypted input data stream for transmission in a communications network, the instructions comprising:
 instructions executable by a processor to encode the encrypted input data stream using a substitution cipher to produce an encoded data stream, the encoded data stream having a lower information density than the encrypted input data stream.   
     
     
         2 . The non-transitory processor-readable storage medium of  claim 1 , wherein the instructions executable to encode the encrypted data using a substitution cipher comprise instructions executable to expand triplets of a first number of bits to quads of a second number of bits. 
     
     
         3 . The non-transitory processor-readable storage medium of  claim 1 , wherein the substitution cipher is a monoalphabetic substitution based on a secret alphabet. 
     
     
         4 . The non-transitory processor-readable medium of storage  claim 1 , wherein the substitution cipher is a polyalphabetic substitution based on multiple secret alphabets. 
     
     
         5 . The non-transitory processor-readable storage medium of  claim 1 , wherein the substitution cipher uses an ambiguous coding scheme in which at least some of the input data is representable by more than one output character. 
     
     
         6 . The non-transitory processor-readable storage medium of  claim 1 , wherein the encoded data would fail a FIPS 140-2 randomness test. 
     
     
         7 . The non-transitory processor-readable storage medium of  claim 1 , wherein the instructions executable to encode the encrypted input data stream using the substitution cipher comprise instructions executable to:
 divide the encrypted input data stream into a plurality of groups; and   map each group to a character in a set of characters.   
     
     
         8 . The non-transitory processor-readable storage medium of  claim 7 , wherein the set of characters is derivable from a set of encryption keys using a pseudorandom function. 
     
     
         9 . A non-transitory processor-readable storage medium storing instructions for execution by a processor to decode an encoded encrypted data stream received over a communications network, the instructions comprising:
 instructions executable to use a substitution cipher to decode the encoded encrypted data stream to produce a decoded encrypted data stream, the decoded encrypted data stream having a higher information density than the encoded encrypted data stream.   
     
     
         10 . The non-transitory processor-readable storage medium of  claim 9 , wherein the encoded encrypted data stream comprises characters in a set of characters, the instructions comprising instructions executable to map each character to a group of bits of the decoded encrypted data stream. 
     
     
         11 . The non-transitory processor-readable storage medium of  claim 10 , wherein the substitution cipher is an alphabetic substitution based on at least one secret alphabet. 
     
     
         12 . The non-transitory processor-readable storage medium of  claim 10 , wherein the substitution cipher is a monoalphabetic substitution based on a secret alphabet. 
     
     
         13 . The non-transitory processor-readable storage medium of  claim 10 , wherein the substitution cipher is a polyalphabetic substitution based on multiple secret alphabets. 
     
     
         14 . The non-transitory processor-readable storage medium of  claim 10 , wherein the substitution cipher uses an ambiguous coding scheme in which at least some of the input data is representable by more than one output character. 
     
     
         15 . The non-transitory processor-readable storage medium of  claim 10 , wherein the set of characters is derivable from a set of encryption keys using a pseudorandom function.