WebCrypt MCP Server — Claude Code MCP server setup
Adds cryptographic primitives directly to AI coding agents via Web Crypto API. It runs with zero runtime dependencies on Node.js 18 or newer.
claude mcp add webcrypt -- npx -y webcryptWhat WebCrypt MCP Server does
This server gives coding agents a local security toolkit. It handles symmetric AES-256-GCM encryption, RSA-4096 hybrid public keys, and SHA hashing digests. It also includes post-quantum algorithms such as Kyber and Dilithium. Agents can encrypt tokens before saving them to disk.
Six tools handle cryptographic workflows: encrypt_payload, decrypt_payload, manage_keys, crypto_hash, sign_verify, and pqc_kem_sign. Everything relies on the native crypto.subtle engine. No extra packages are needed.
The server expects Node.js 18 or higher. Without runtime Web Crypto support, calls fail immediately.
What it helps with
- encrypt agent secrets before writing files to disk
- sign code diffs and release builds with digital signatures
- generate ephemeral JWK keypairs for agent communication
- calculate cryptographic hashes using SHA-256 or SHA-512
Example prompts for the agent
- Generate a fresh RSA-4096 keypair using
manage_keysand display the public key - Encrypt the
.envcontents usingencrypt_payloadwith symmetric AES-256-GCM - Verify the release bundle hash with
sign_verify
How to install WebCrypt MCP Server
Platform CLI
claude mcp add webcrypt -- npx -y webcryptPlatform CLI
codex mcp add webcrypt-mcp-server -- npx -y webcryptConfig file
{
"mcpServers": {
"webcrypt-mcp-server": {
"command": "npx",
"args": [
"-y",
"webcrypt"
]
}
}
}Config file
{
"servers": {
"webcrypt-mcp-server": {
"type": "stdio",
"command": "npx",
"args": [
"-y",
"webcrypt"
]
}
}
}Platform CLI
gemini mcp add webcrypt-mcp-server npx -y webcryptStep by step, with commands for each platform: How to add an MCP server to Claude Code, Codex, Cursor, VS Code, Gemini CLI and more
Questions about WebCrypt MCP Server
How do I install WebCrypt MCP Server in Claude Code?
Run claude mcp add webcrypt -- npx -y webcrypt in your terminal.
What tools are included in WebCrypt MCP Server?
It provides six tools: encrypt_payload, decrypt_payload, manage_keys, crypto_hash, sign_verify, and pqc_kem_sign.
Does WebCrypt MCP Server require third-party cryptographic libraries?
No external libraries are needed. The server executes entirely through native crypto.subtle on Node.js 18 and newer.
