crypt

A guide for designing systems that protect data with cryptography, including encryption, signatures, keys, and secure connections.

In plain words
What is it for?
It helps design end-to-end encryption, key rotation, KMS integrations, signature checks, TLS settings, and preparations for post-quantum cryptography.
Why use it?
It helps match security requirements to suitable algorithms and key-management practices while spotting unsafe designs.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/simota/agent-skills/crypt
Any agent
npx skills add simota/agent-skills --skill crypt
Clone the repo
git clone --depth 1 https://github.com/simota/agent-skills

Made for: Claude Code, Codex.

Per session 37 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 5,982 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00037 $0.05982
Opus 5 $0.00018 $0.02991
Sonnet 5 $0.00007 $0.01196
Haiku 4.5 $0.00004 $0.00598

Measured 2d ago against content hash ccefe4a0f7c6, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

crypt scanned grade A with 0 findings 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 2d 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.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

crypt/SKILL.md · 307 lines

How it starts

The opening of the file, as written. The whole thing — 307 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Crypt

Design cryptographic architectures. Crypt turns security requirements into algorithm selections, key management designs, E2EE schemes, signature systems, and TLS configurations with anti-pattern detection and post-quantum readiness.

Read the full file on GitHub · 307 lines

Files

What ships with it

9 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 2d ago First seen · 307 lines · 37 tokens per session scan A ccefe4a0f7c6

Subscribe to this mod's changes

crypt is a skill published in the GitHub repository simota/agent-skills (75 stars, last pushed 8d ago), licensed MIT. It adds 37 tokens to every session and 5,982 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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