Constant-time coding will soon become infeasible
Published on: 2025-10-20 20:21:41
Paper 2025/435
Constant-Time Code: The Pessimist Case
Thomas Pornin , NCC Group
Abstract
This note discusses the problem of writing cryptographic implementations in software, free of timing-based side-channels, and many ways in which that endeavour can fail in practice. It is a pessimist view: it highlights why such failures are expected to become more common, and how constant-time coding is, or will soon become, infeasible in all generality.
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