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Checking that functions are constant time with Valgrind (2010)
(01 Apr 2010) Information leaks via timing side channels can be deadly. You can steal RSA keys from other processes on the same host, extract the kernel's dm_crypt keys and steal AES keys over the network.
In order for a function to be constant time, the branches taken and memory addresses accessed must be independent of any secret inputs. Since cryptographic functions result in abnormally straight line code, it's common for a typical input to exercise every instruction. So a tool like Valgrind could check all the branches and memory accesses to make sure that they haven't been tainted with secret data.
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