crypto-protocol-diagram

crypto-protocol-diagram is a skill for Claude Code from RedHatProductSecurity/prodsec-skills. It costs 120 tokens per session (4,682 once invoked), scanned A, original, Apache-2.0.

A tool that turns a cryptographic protocol into a Mermaid sequence diagram, showing who sends each message, what cryptographic operation is applied, and which phase of the exchange it belongs to. A cryptographic protocol is a set of steps used by computers to exchange messages or keys securely.

In plain words
What is it for?
Visualizing protocols such as TLS, Noise, Signal, X3DH, or FROST, and producing both a Mermaid diagram file and an inline text diagram.
Why use it?
It makes handshakes and key exchanges easier to follow when they are buried in source code, an RFC, a research paper, informal notes, or a formal model.

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 Visualizing protocols such as TLS, Noise, Signal, X3DH, or FROST, and producing both a Mermaid diagram file and an inline text diagram.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/redhatproductsecurity/prodsec-skills/crypto-protocol-diagram
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 crypto-protocol-diagram
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 crypto-protocol-diagram

README.md
[![agentmods](https://agentmods.dev/badge/skills/redhatproductsecurity/prodsec-skills/crypto-protocol-diagram/github.svg)](https://agentmods.dev/skills/redhatproductsecurity/prodsec-skills/crypto-protocol-diagram)
Your own site
<a href="https://agentmods.dev/skills/redhatproductsecurity/prodsec-skills/crypto-protocol-diagram"><img src="https://agentmods.dev/badge/skills/redhatproductsecurity/prodsec-skills/crypto-protocol-diagram/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for crypto-protocol-diagram

Your own site · 80×15
<a href="https://agentmods.dev/skills/redhatproductsecurity/prodsec-skills/crypto-protocol-diagram"><img src="https://agentmods.dev/badge/skills/redhatproductsecurity/prodsec-skills/crypto-protocol-diagram.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 120 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 4,682 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 1 finding, up to high

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • high Prompt Injection · line 291
    Hidden instructions were detected in comments or invisible text. These could contain malicious directives. Manual review is recommended.
    Fix: Audit all comments and invisible characters. Remove any instructions that direct the agent to perform unauthorized actions. Use plain, reviewable content.
How audits are shown
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 $0.00120 $0.04682
Opus 5 $0.00060 $0.02341
Sonnet 5 $0.00024 $0.00936
Haiku 4.5 $0.00012 $0.00468

Measured 12d ago against content hash f56238cb7f64, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

crypto-protocol-diagram 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 12d 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.

module/skills/crypto-protocol-diagram/SKILL.md · 435 lines

How it starts

The opening of the file, as written. The whole thing — 435 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Crypto Protocol Diagram

Produces a Mermaid sequenceDiagram (written to file) and an ASCII sequence diagram (printed inline) from either:

  • Source code implementing a cryptographic protocol, or
  • A specification — RFC, academic paper, pseudocode, informal prose, ProVerif (.pv), or Tamarin (.spthy) model.

Unlike the diagramming-code skill (which visualizes code structure), this skill extracts protocol semantics: who sends what to whom, what cryptographic transformations occur at each step, and what protocol phases exist.

For call graphs, class hierarchies, or module dependency maps, use the diagramming-code skill instead.

When to Use

  • User asks to diagram, visualize, or extract a cryptographic protocol
  • Input is source code implementing a handshake, key exchange, or multi-party protocol
  • Input is an RFC, academic paper, pseudocode, or formal model (ProVerif/Tamarin)
  • User names a specific protocol (TLS, Noise, Signal, X3DH, FROST)

When NOT to Use

  • User wants a call graph, class hierarchy, or module dependency map — use diagramming-code
  • User wants to formally verify a protocol — use mermaid-to-proverif (after generating the diagram)
  • Input has no cryptographic protocol semantics (no parties, no message exchange)

Rationalizations to Reject

Rationalization Why It's Wrong Required Action
"The protocol is simple, I can diagram from memory" Memory-based diagrams miss steps and invert arrows Read the source or spec systematically
"I'll skip the spec path since code exists" Code may diverge from the spec — both paths catch different bugs When both exist, run spec workflow first, then annotate code divergences
"Crypto annotations are optional decoration" Without crypto annotations, the diagram is just a message flow — useless for security review Annotate every cryptographic operation
"The abort path is obvious, no need for alt blocks" Implicit abort handling hides missing error checks Show every abort/error path with alt blocks
"I don't need to check the examples first" The examples define the expected output quality bar Study the relevant example before working on unfamiliar input
"ProVerif/Tamarin models are code, not specs" Formal models are specifications — they describe intended behavior, not implementation Use the spec workflow (S1–S5) for .pv and .spthy files

Read the full file on GitHub · 435 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. 12d ago First seen · 435 lines · 120 tokens per session scan A f56238cb7f64

Subscribe to this mod's changes

crypto-protocol-diagram is a skill published in the GitHub repository RedHatProductSecurity/prodsec-skills (52 stars, last pushed 1mo ago), licensed Apache-2.0. It adds 120 tokens to every session and 4,682 once invoked, about $0.0006 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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