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Cryptographers believe size does matter to stay safe online

Posted on 07/12/2011
Professor K Paterson

Professor Kenny Paterson

With people using computers as part of their everyday lives to communicate, buy goods or for banking, ensuring our details are protected from online thieves remains one of our biggest concerns.

Researchers from Royal Holloway, University of London are analysing a new security system called Transport Layer Security (TLS), which is designed to help protect our details, to identify any weaknesses in it and ensure it is doing its job properly to give us greater confidence online. The findings are outlined in a research paper entitled ‘Tag Size Does Matter: Attacks and Proofs for the TLS Record Protocol’ which will be presented at a week-long AsiaCrypt Conference in Korea, which starts today (Monday 5 December).

One of these researchers, Professor Kenny Paterson from the Information Security Group (ISG) at Royal Holloway, said: “Web users may not have heard of TLS and won’t know that the system is in place to help protect our private details from hackers and online thieves. Our analysis of TLS version 1.2 gives us higher confidence that the data we share online will be kept safe, secure and private”.

The only real evidence of the hidden security system for web users is when your web browser says ‘https’, rather than ‘http’, which is when the TLS system comes into play. TLS encrypts the messages as they are sent across the Internet, keeping our personal data safe from attackers.

However, the researchers did find a new vulnerability in the latest version of the system. Professor Paterson explains: “There is still scope for a ‘distinguishing attack’ against TLS 1.2, where an attacker could tell whether a user has sent a ‘yes’ or a ‘no’ during a transaction, for example.

“This kind of attack is usually considered a bit theoretical, but it can point to more serious underlying security issues.

“Fortunately, in the TLS case, this attack should never arise in practice. TLS uses something called a Message Authentication Code (MAC) tag to help provide security, and for our attack to work, we would need the MAC tag to be small. In short, our work proves that size does matter.”

Professor Paterson concluded: “In 2002, TLS 1.0 came under fire after researchers found a distinguishing attack against the system. In September 2011, the same basic idea was used to mount a much more serious attack against TLS 1.0, under the colourful name of the BEAST attack. So now the industry is finally getting ready to make the switch to TLS 1.2. We can have higher confidence in this latest version of TLS because of our work.”



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