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By | John Leyden 25th July 2008 18:19

Austrian official fuels Skype backdoor rumours

'No particular problems' to listening in

Off the cuff remarks by Austrian government officials suggest that Skype conversations might be intercepted.

Speaking at a recent meeting on lawful interception between ISPs and Austrian regulators, an unnamed "high-ranking" official at Austria's interior ministry said that listening into a conversation over Skype presented no particular problems, Heise security reports.

The opinion contrasts with the view of Joerg Ziercke, president of Germany's Federal Police Office (BKA). At a meeting last November Ziercke said that the inability to decipher the encryption used by Skype in order to intercept VoIP calls had become a problem in counter-terrorism investigations. Weeks after this, leaked documents outlining plans by German firm Digitask to develop software to intercept Skype VoIP communications and SSL transmissions, along with related costing and licensing proposals, surfaced through Wikileaks.

Skype runs using a proprietary protocol. Unlike Phil Zimmermann's Zfone project, for example, its source code has not been publicly released. So even though Skype has commissioned security experts to audit its technology (which incorporates trusted encryption techniques, such as Advanced Encryption Standard, to encrypt conversations and RSA for key negotiation) doubts have remained.

For example, security experts Philippe Biondi and Fabrice Desclaux have voiced concerns) that Skype has the keys to decrypt calls or sessions, a claim Skype denies.

Access to such keys would provide backdoor access to conversations but it's worth remembering, as is the case with warrants for regular phone conversations, that law enforcement agencies are more often interested in knowing who an investigative target is talking to than what they are saying. Skype offers confidentiality, but it makes no claims of offering anonymity.

For example two years ago, a fugitive chief exec was tracked to Sri Lanka after his location was given away by a conversation made using Skype. Papers on tracking anonymous peer-to-peer VoIP traffic provide clues on how this might have been accomplished. ®

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