constant-time-testing

constant-time-testing is a skill for Claude Code from RedHatProductSecurity/prodsec-skills. It costs 25 tokens per session (4,804 once invoked), scanned B, original, Apache-2.0.

A testing approach for finding timing side channels in cryptographic code. A timing side channel is a secret leak caused by observable differences in how long code takes to run.

In plain words
What is it for?
Use it when auditing cryptographic implementations for execution-time differences related to secret data.
Why use it?
It helps reveal implementation flaws that could expose private keys even when the underlying cryptographic algorithm is sound.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the prodsec-skills plugin — 133 skills shipped together

Good fit Use it when auditing cryptographic implementations for execution-time differences related to secret data.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/redhatproductsecurity/prodsec-skills/constant-time-testing
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add RedHatProductSecurity/prodsec-skills --skill constant-time-testing
Clone the repo
git clone --depth 1 https://github.com/RedHatProductSecurity/prodsec-skills

Made for: Claude Code.

Or install prodsec-skills, the plugin that ships this one along with the rest of its 133 skills.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for constant-time-testing

README.md
[![agentmods](https://agentmods.dev/badge/skills/redhatproductsecurity/prodsec-skills/constant-time-testing.svg)](https://agentmods.dev/skills/redhatproductsecurity/prodsec-skills/constant-time-testing)
Your own site
<a href="https://agentmods.dev/skills/redhatproductsecurity/prodsec-skills/constant-time-testing"><img src="https://agentmods.dev/badge/skills/redhatproductsecurity/prodsec-skills/constant-time-testing.svg" alt="Measured on agentmods" height="20"></a>
Per session 25 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 4,804 The whole file, excluding the scripts and references it only reads on demand.
Security scan B 1 finding. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00025 $0.04804
Opus 5 $0.00013 $0.02402
Sonnet 5 $0.00005 $0.00961
Haiku 4.5 $0.00003 $0.00480

Measured 8d ago against content hash 034a65a1d957, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade B, and why

constant-time-testing scanned grade B with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 8d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Harvests environment variablesmediumData exfiltration

Enumerating or grepping the environment for keys collects credentials unrelated to what the mod says it does.

Timing attacks exploit variations in execution time to extract secret information from cryptographic implementations. Unlike cryptanalysis that targets theoretical weaknesses, timing attacks leverage implementation flaws

Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.

Origin

Copies of this mod

1 near-identical copy found in the catalogue:

module/skills/constant-time-testing/SKILL.md · 511 lines

How it starts

The opening of the file, as written. The whole thing — 511 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Constant-Time Testing

Timing attacks exploit variations in execution time to extract secret information from cryptographic implementations. Unlike cryptanalysis that targets theoretical weaknesses, timing attacks leverage implementation flaws - and they can affect any cryptographic code.

Background

Timing attacks were introduced by Kocher in 1996. Since then, researchers have demonstrated practical attacks on RSA (Schindler), OpenSSL (Brumley and Boneh), AES implementations, and even post-quantum algorithms like Kyber.

Key Concepts

Concept Description
Constant-time Code path and memory accesses independent of secret data
Timing leakage Observable execution time differences correlated with secrets
Side channel Information extracted from implementation rather than algorithm
Microarchitecture CPU-level timing differences (cache, division, shifts)

Why This Matters

Timing vulnerabilities can:

  • Expose private keys - Extract secret exponents in RSA/ECDH
  • Enable remote attacks - Network-observable timing differences
  • Bypass cryptographic security - Undermine theoretical guarantees
  • Persist silently - Often undetected without specialized analysis

Two prerequisites enable exploitation:

  1. Access to oracle - Sufficient queries to the vulnerable implementation
  2. Timing dependency - Correlation between execution time and secret data

Common Constant-Time Violation Patterns

Four patterns account for most timing vulnerabilities:

// 1. Conditional jumps - most severe timing differences
if(secret == 1) { ... }
while(secret > 0) { ... }

// 2. Array access - cache-timing attacks
lookup_table[secret];

// 3. Integer division (processor dependent)
data = secret / m;

// 4. Shift operation (processor dependent)
data = a << secret;

Read the full file on GitHub · 511 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 8d ago First seen · 511 lines · 25 tokens per session scan B 034a65a1d957

Subscribe to this mod's changes

constant-time-testing is a skill published in the GitHub repository RedHatProductSecurity/prodsec-skills (52 stars, last pushed 1mo ago), licensed Apache-2.0. It adds 25 tokens to every session and 4,804 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it B with 1 finding (harvests environment variables). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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