In association with heise online

04 July 2012, 11:38

John the Ripper now able to crack office files and use GPUs

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Padlock broken icon Version 1.7.9-jumbo-6 of the John the Ripper password cracker sees significant format support enhancements. The open source tool is now able to crack password-protected office documents (Office 2007/2010 and OpenDocument) and Firefox, Thunderbird and SeaMonkey master passwords, as well as WPA-PSK keys and Mac OS X keychains. It can also request to use GPUs via CUDA and OpenCL. The suffix "jumbo" appears to be intended literally – more than 40,000 lines of code have been added in the six months since the previous release.

Developer Solar Designer told The H's associates at heise Security that, in developing GPU support, the focus has been on modern functions which can be slow to calculate, such as WPA-PSK and Unix password hashes. For some functions, such as Ubuntu's standard hash function (sha512crypt) and the time-consuming bcrypt, there were, according to the developers, no crackers with GPU support until now, "because others were unhappy about releasing a tool with 'non-impressive' speed numbers, even if this is desirable in practice".

In the case of sha512crypt, this means that the GPU on a GeForce GTX 570 graphics card can generate around 11,000 hashes per second – still more than five times faster than on a computer with eight CPU cores. By comparison, for SHA1 hashes, with GPU support this figure would normally be in the millions. For bcrypt, a graphics card just beats an eight-core system by a hair's breadth – in both cases the maximum figure is around 5,000 hashes. The inability of GPUs to realise speed gains with bcrypt is due to the algorithm's design, which is very memory intensive. According to Solar Designer, the developers were primarily concerned with finding out just how slow the bcrypt implementation would be.

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