Cipher mixer with random number generator

DETAILED DESCRIPTION This invention solves these and other problems by providing a combination block cipher with an effective key length greater than that of its components.
This invention increases the security provided by any single block cipher by providing encryption of an input stream by at least two different block ciphers.
To add to the security, a one-time pad in the form of a random data stream, is combined with an encrypted form of the input stream before it is encrypted by the second block cipher.
In one aspect, this invention is an encryption device which has a random number generator and three block cipher mechanisms.
The first block cipher mechanism takes a plaintext input and produces a first enciphered output based on the plaintext and on a first key.
An exclusive-or mechanism takes as input the first enciphered output from the first block cipher and the output of the random number generator and produces a combined output.
The second block cipher mechanism takes as input the output of the exclusive-or mechanism and produces a second enciphered output based on the output of the exclusive-or mechanism and on a second key.
The third block cipher mechanism takes as input the output of the random number generator and produces a third enciphered output based on the output of the random number generator and on a third key.
The first and second block cipher mechanisms differ from each other, with one preferably being the IDEA block cipher, and the other preferably being the Blowfish block cipher.
Preferably the first and third block cipher mechanisms are Blowfish block ciphers and the second block cipher is the IDEA block cipher.
The plaintext input is preferably a sequence of 64-bit values and the output of the random number generator is a sequence of 64-bit random values.
Preferably the random number generator is a true random number generator.
In another aspect, this invention is the decryption device corresponding to the encryption device.
This invention's combination of block ciphers with random numbers has a number of advantages, including: Cryptanalysis based on known characteristics of the plaintext is impossible