US Patent 8345876 Encryption/decryption system and method

A method of encrypting a plain text message that is m characters in length is described. A one off random key having a length of m characters is generated. The random key uses a character set and modulus that is compatible with the plain text message. A first substitution encryption of the plain text message is performed using the generated random key. A string of random fill characters that is f characters in length, f being a number between zero and infinity is generated. The generated random key and the string of random fill characters is concatenated to the encrypted plain text message to generate an encrypted message string. The encrypted message string has a length 2m+f. The encrypted message string is transmitted to a receiver.