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Last Updated: Thursday, 8 April, 2004, 15:59 GMT 16:59 UK
Experts talk up text security
By Mark Ward
BBC News Online technology correspondent

Mobile phone users concerned that David Beckham's much publicised troubles mean their text messages are not safe from prying eyes can stop worrying.

Text message on mobile phone, PA
Text messages are hard to intercept
On 4 April the News of the World published a story about Beckham's private life and partly based its allegations on phone text messages.

The story has been rejected as "ludicrous" by Beckham.

The group representing the mobile phone industry and SMS experts said it would be practically impossible to spy on text messages by eavesdropping.

"We are unaware of any particular eavesdropping methods that exist for text messages," said a spokesman for the GSM Association which acts as the industry voice for the most widely used mobile phone technology.

He said the industry association understood that the text messages in the story were simply handed to the News of the World by a "friend" of the woman at the centre of the allegations.

"We are not sure that any journalist could eavesdrop on text messages," he said.

Scrambling system

Text messages are protected "in-flight" between phones because they are encrypted using the A5 algorithm.

However, academic researchers have demonstrated weaknesses in this scrambling system at least twice in the last five years.

David Beckham, AP
Beckham: Rejected allegations
One research paper pointed out potential loopholes in the way that the GSM mobile phone system scrambles calls.

Another, separate, paper by Professor Eli Biham, Elad Barkan and Natan Keller of Israel's Technion Institute of Technology in Haifa demonstrated a way to eavesdrop on conversations.

Neither paper talked about the feasibility of intercepting SMS messages.

Andrew Bud, head of messaging firm MBlox, said the practical difficulties involved in using these methods made it all but impossible to snatch text messages out of the air.

In response to the weaknesses identified in the papers the encryption system for GSM phones was improved to make it harder to mount successful attacks.

Paid access

The only other route available to those keen to read someone else's text messages is to consult the computers used by operators to keep records of who sent which message to whom and when they sent it.

Mr Bud said mobile phone firms kept records of text messages to ensure that bills are calculated correctly.

They hung on to the messages to ensure they can resolve disputes. For instance customers may complain that they did not send messages they were being billed for or that they had sent texts that did not arrive.

These records are kept for a few weeks or months, depending on the operator and the data protection regime operating in that nation.

Mr Bud said that if an employee looked up text messages and passed them to someone else it would be a gross violation of that company's operating guidelines.

But the spokesman for the GSM Association doubted that even this would be successful.

"We do not believe that operators retain the content of messages," he said "they simply retain routing and billing information."

Beckham 'still a role model'
05 Apr 04  |  Education
Troubles with trans-Atlantic text
05 Apr 04  |  Technology
Mystery of missing text messages
25 Mar 02  |  dot life
Texting improves sex life
15 Apr 02  |  Science/Nature


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