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Old 4th January, 2010, 05:37 PM
Aedan Aedan is offline
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Join Date: September 2001
Location: Europe
Posts: 13,075

A5/1 is one of several algorithms used to protect speech on a GSM network. One other alternative is A5/3, which uses 128bit encryption. Incidentally, A5/3 is already used to protect GPRS traffic (data, rather than voice).

However, GSM has some serious design deficiencies that mean it's not really suitable for secure communications. For example, GSM requires a mobile phone to authenticate to the network before it can operate. There's no provision for the network to authenticate to the mobile phone, so you have no idea who's network you're actually connected to. That could well be an easier attack than breaking the encryption used.

UMTS (3G) uses a different cipher, and currently stands up to cryptoanalysis. Ultimately, it is a matter of time before a form of encryption is broken. An attack that takes 100 years with this year's hardware will only take 50 years with next year's hardware.

The A5/1 encryption used has survived pretty well, given how much more powerful computers are now than they were 21 years ago. 21 years ago, the 8086 was just about around, as was the 68000.

Last edited by Áedán; 4th January, 2010 at 05:38 PM.
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