ALTCHA proof-of-work captcha

Generated from mcp/patterns.registry.json — do not edit by hand; change the registry and run bun run patterns:build.

Index card — the docs below are the canonical explanation; deep-tier pattern pages additionally carry invariants and emulation notes.

Category: Anti-Abuse · Tier: light · Risk: medium — bot/abuse defense; misconfiguration or kill-switch misuse weakens protection

A self-hosted proof-of-work captcha where the client solves a CPU-bound puzzle and the server verifies an HMAC-signed payload via altcha-lib.

When to use: Reach for it on public forms that need bot resistance without third-party captcha services or extra user interaction.

Docs

• docs/blueprint/abuse/captcha.md (GitHub · GitLab)

Code

• src/lib/server/abuse/altcha.ts (GitHub · GitLab)
• src/lib/components/composites/altcha/ (GitHub · GitLab)

Proof

• /showcases/abuse/captcha

Machine-readable record: anti-abuse-captcha in mcp/patterns.registry.json.