3 ms·

> In cryptography the term "constant time" is sometimes used to mean a different concept, that the operation actually takes constant non-varying time, so that a

> In cryptography the term "constant time" is sometimes used to mean a different concept, that the operation actually takes constant non-varying time, so that an attacker can't exploit this as a side channel to figure out the input values. Note that I cited Thomas Pornin for my definition of constant time cryptography, who is a cryptographer in theory and implementation. It is emphatically not necessary for software to run with unvarying execution time in order for it to be "constant time" according to the cryptographic sense of the term. This will be a poor hill for you to die on, but I invite you to provide literature supporting your alternative definition.

infinity0x-2 7y ago
> This will be a poor hill for you to die on, but I invite you to provide literature supporting your alternative definition. Lol, you are being melodramatic, this is just some algorithms. Thomas Pornin says: > more precisely, that variations in execution time are not correlated with secret elements: execution time may still vary, but not in a way that can be traced back to any kind of value that you wish to keep secret, What I said: > what the operation actually takes constant non-varying time, so that an attacker can't exploit this as a side channel to figure out the input values. We basically said the same thing, but you are choosing to nit-pick my precise wording. Sure the execution can vary according to public inputs. The subject of this thread (the paper) doesn't talk about whether inputs are secret or public, but the "constant time" part of it is only interesting if the inputs are secret, and under this context it means "non-varying". The people that downvoted my previous post are idiots.