Although A5/4 was developed and clearly specified at the same time as A5/3, there are no known mobile network providers who have implemented this, as of today. For more information please see the Specification of the A5/4 Encryption Algorithms and GSMA Security Algorithms. Because of schedule pressures in 3GPP standardization, instead of developing a new cipher, SAGE agreed with 3GPP technical specification group (TSG) for system aspects of 3G security (SA3) to base the development on an existing algorithm that had already undergone some evaluation.īased on A5/3, the only essential change is the external key length input from 64 bits to 128 bits.

KASUMI was designed for 3GPP to be used in UMTS security system by the Security Algorithms Group of Experts (SAGE), a part of the European standards body ETSI. The cipher is based around a combination of four linear feedback shift registers with irregular clocking and a non-linear combiner. A5/2 was a deliberate weakening of the algorithm for certain export regions.

Is a stream cipher used to provide voice privacy in the GSM cellular telephone protocol. A5/1 is used in Europe and the United States. A number of serious weaknesses in the cipher have been identified. It was initially kept secret, but became public knowledge through leaks and reverse engineering. Is a stream cipher used to provide over-the-air communication privacy in the GSM cellular telephone standard.

A5/4: The essential change is the key length input from 64 bits to 128 bits.

A5/3: Even stronger ciphering with open design, also called KASUMI.

A5/2: Weak ciphering, intended for other countries, now deprecated by GSMA.

A5/1: Strong(er) ciphering, intended for use in North America and Europe.

There are four variants of A5 in GSM, only the first three are widely deployed: For technical details and attacks see the Cryptome GSM Files. The GSM ciphering algorithm is called A5. This page shall help you understand all the abbreviations we use in our project.

Tetra sms