Design and implementation of Rijndael algorithm for GSM encryption

Encryption is used in communications systems to protect information being transmitted over a channel from being intercepted and read by unauthorised parties. This protection is achieved by converting the original message (plain text) into an encoded form (cipher text) that appears to be a random stream of symbols. A5 is the encryption algorithm used in order to ensure privacy of conversations on GSM mobile phones. Two versions of the stream cipher are available. The strong version, A5/1, is used in most countries while the weaker A5/2 is used in countries on which export restrictions apply. In the third quarter of 2002, ETSI published GSM´s new security algorithm, known as A5/3. A5/3 is based on the Kasumi algorithm, specified by 3GPP for use in 3G mobile systems. In this same period the Rijndael algorithm was being discussed in the cryptographic community for its use in mobile security. In this work it will be shown that a modified A5/3 based on Rijndael provides a higher level of security than A5/1 and even the original A5/3.