Measures timing side channels in cryptographic implementations by running them, using dudect for statistical analysis and Timecop over Valgrind for dynamic tracing. Covers the formal, symbolic, dynamic, and statistical tool categories and how to read a result.
Install
npx skills add trailofbits/skills --skill constant-time-testingnpx skills add trailofbits/skills --skill constant-time-testing -a claude-code -gnpx skills add trailofbits/skills --skill constant-time-testing -a codex -ggemini skills install https://github.com/trailofbits/skills.git --path plugins/testing-handbook-skills/skills/constant-time-testinggh skill install trailofbits/skills constant-time-testinggit clone --depth 1 https://github.com/trailofbits/skills /tmp/trailofbits__skills
mkdir -p ~/.claude/skills ~/.agents/skills
cp -R /tmp/trailofbits__skills/plugins/testing-handbook-skills/skills/constant-time-testing ~/.claude/skills/constant-time-testing # Claude Code
cp -R /tmp/trailofbits__skills/plugins/testing-handbook-skills/skills/constant-time-testing ~/.agents/skills/constant-time-testing # Codex, Cursor, Gemini CLI, Copilot, OpenCode