webcrypt-mcp

A skill for using WebCrypt MCP, a server that provides encryption, key creation, digital signatures, hashing, and post-quantum cryptography.

In plain words
What is it for?
Use it to encrypt saved sensitive data, generate keys, sign or verify artifacts, and calculate hashes or HMAC tags.
Why use it?
It provides defined cryptographic steps for protecting sensitive credentials, tokens, private workflow data, and verifiable outputs.

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/putervision/webcrypt/webcrypt-mcp
Any agent
npx skills add putervision/WebCrypt --skill webcrypt-mcp
Clone the repo
git clone --depth 1 https://github.com/putervision/WebCrypt

Made for: Claude Code, Codex.

Per session 58 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,070 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 $0.00058 $0.01070
Opus 5 $0.00029 $0.00535
Sonnet 5 $0.00012 $0.00214
Haiku 4.5 $0.00006 $0.00107

Measured 2d ago against content hash 6e091f5bd787, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

webcrypt-mcp 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.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/exercise_tools.js), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

.agents/skills/webcrypt-mcp/SKILL.md · 49 lines

How it starts

The opening of the file, as written. The whole thing — 49 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Cryptographic Memory & Vault Tooling (webcrypt-mcp)

This project provides webcrypt-mcp, a native Model Context Protocol server for zero-dependency AES-256-GCM encryption, RSA-4096 hybrid public-key encryption, digital signatures, cryptographic hashes, and post-quantum cryptography.

1. Mandatory Workflow & Priority

  1. Confidential Artifacts: Whenever saving sensitive credentials, tokens, or private workflow states, encrypt them using encrypt_payload(mode: "data", password: "...") or encrypt_payload(mode: "symmetric", password: "...").
  2. Key Management: Use manage_keys(action: "generate", type: "rsa" | "ecdh" | "ecdsa" | "rsa-pss" | "hmac") to generate cryptographically strong JWK-formatted keys for inter-agent communication.
  3. Integrity & Signatures: Before completing tasks that produce verifiable evidence (such as evidence packs or release binaries), compute signatures or HMAC tags using sign_verify(action: "sign", algorithm: "ECDSA" | "HMAC").
  4. Triple Memory Triad:
    • state-memory-mcp: Workflow state tracking.
    • vision-memory-mcp: Visual state caching.
    • webcrypt-mcp: Encryption of sensitive DAG nodes, visual cache database vaults, and signature verification.

2. Complete Tool Reference

Tool Name Key Inputs Description
encrypt_payload mode ('symmetric' | 'asymmetric' | 'data'), data, password?, public_key_jwk? Encrypt plaintext, JSON object, or binary data.
decrypt_payload mode ('symmetric' | 'asymmetric' | 'data'), ciphertext, password?, private_key_jwk? Decrypt ciphertext back to plaintext or structured JSON.
manage_keys action ('generate' | 'generate_random_password'), type ('rsa' | 'ecdh' | 'ecdsa' | 'rsa-pss' | 'hmac'), modulusLength?, namedCurve?, length? Generate cryptographic keys (JWK format) or secure random passwords.
crypto_hash algorithm ('SHA-256' | 'SHA-384' | 'SHA-512' | 'SHA3-256' | 'SHA3-512'), data, encoding ('hex' | 'base64') Compute cryptographic hash digests.
sign_verify action ('sign' | 'verify'), algorithm ('ECDSA' | 'RSA-PSS' | 'HMAC' | 'HMAC-SHA3'), data, signature?, password?, key_jwk? Sign or verify messages with ECDSA, RSA-PSS, or HMAC.
pqc_kem_sign action ('generate_kyber_keypair' | 'kyber_encapsulate' | 'kyber_decapsulate' | 'hybrid_encapsulate' | 'hybrid_decapsulate' | 'generate_dilithium_keypair' | 'dilithium_sign' | 'dilithium_verify'), level?, public_key_b64?, private_key_b64?, ... Post-quantum Kyber KEM, Dilithium signatures, and Hybrid KEM.

Read the full file on GitHub · 49 lines

Files

What ships with it

2 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 · 49 lines · 58 tokens per session scan A 6e091f5bd787

Subscribe to this mod's changes

webcrypt-mcp is a skill published in the GitHub repository putervision/WebCrypt (24 stars, last pushed 11d ago), licensed MIT. It adds 58 tokens to every session and 1,070 once invoked, about $0.0003 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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