Randomised web numbers are too easy to guess
Previously unknown encryption flaw could mean data is stolen more readily, claim researchers
A group of security researchers has revealed that the randomised numbers used to encrypt data on the web could be too weak to offer high levels of protection.
The flaw, which prevents servers from generating strong encryption, was discovered by security researchers Bruce Potter and Sasha Moore, who presented their research at the annual Black Hat conference in Las Vegas.
Potter explained that the randomly generated data strings are produced by the server, which detects when certain computer behaviour such as mouse movements and keyboard strokes are made. It converts these into ones and zeros and moves this into a pool of data, which is called upon when security functions are needed.
He used the example of a pack of cards to explain how the numbers are selected, saying an unshuffled pack has low randomisation (entropy) because it is easy to predict in what order the cards would be dealt. Data pools used for encryption should have a high entropy, because there is such a wide variety of numbers to be chosen.
But, the entropy of widely-used Linux web servers is lower than first thought because the machines from which the data comes from are not creating enough information to increase the randomisation. The knock-on effect is that systems are struggling to obtain reliable seeds from which to build secure randomised numbers from, which can make the sequence of the strings easier to guess.
According to Potter, this research has shed light on previously unknown aspects of how encryption works on many popular web servers.
"This seemed like just an interesting problem when we got started but as we went on it got scary ... because when you have unknowns in crypto that's when things go sideways," Potter said.
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