ctgrind | Checking that functions are constant time with Valgrind

ctgrind is a C library. ctgrind has no bugs, it has no vulnerabilities and it has low support. You can download it from GitHub.

checking that functions are constant time with valgrind. information leaks via timing side channels can be deadly. you can steal rsa keys from other processes on the same host [1], extract the kernel's dm_crypt keys [2] and steal aes keys over the network [3]. in order for a function to be constant time, the branches taken and memory addresses accessed must be independent of any secret inputs. (that's assuming that the fundamental processor instructions are constant time, but that's true for all sane cpus.). however, it's tough to write constant time functions. you can the source to a few simple ones in [4]. sometimes the design of the function is fundamentally flawed (like aes), but even when the function can be efficiently implemented in a constant time fashion, it's easy to slip up. careful code review is currently the best practice but it's error prone as the amount of code increases and fragile in the face of change. a type system could probably help here, but that's not the path i'm taking today.