# Crypto Protocol Diagram

Extracts protocol message flow from source code, RFCs, academic papers, pseudocode...

- Repository: https://github.com/trailofbits/skills (7935 stars)
- Category: Engineering
- License: CC-BY-SA-4.0
- Last updated: 2026-10-28
- Runs scripts: yes, review before use

## Install

Claude Code: `npx skills add trailofbits/skills --skill crypto-protocol-diagram -g -a claude-code -y`
Codex: `npx skills add trailofbits/skills --skill crypto-protocol-diagram -g -a codex -y`
Cursor: `npx skills add trailofbits/skills --skill crypto-protocol-diagram -g -a cursor -y`
Gemini CLI: `npx skills add trailofbits/skills --skill crypto-protocol-diagram -g -a gemini-cli -y`
Claude Code plugin marketplace: `/plugin marketplace add trailofbits/skills`

## Description

Extracts protocol message flow from source code, RFCs, academic papers, pseudocode, informal prose, ProVerif (.pv), or Tamarin (.spthy) models and generates Mermaid sequenceDiagrams with cryptographic annotations. Use when diagramming a crypto protocol, visualizing a handshake or key exchange flow, extracting message flow from a spec or RFC, diagramming a ProVerif or Tamarin model, or drawing sequence diagrams for TLS, Noise, Signal, X3DH, Double Ratchet, FROST, DH, or ECDH protocols.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# 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.

**Tools used:** Read, Write, Grep, Glob, Bash, WebFetch (for URL specs).

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

The rest: https://github.com/trailofbits/skills/blob/HEAD/plugins/trailmark/skills/crypto-protocol-diagram/SKILL.md