Use Cases

These are current JACS use cases, not speculative integrations.

1. Keep JSON and files verifiable

Use JACS when a report, memory, config, policy, or audit artifact needs to stay verifiable after it leaves the process that created it.

Start with:

What JACS adds:

Self-contained signed envelopes
Re-verification at read time
Cross-language compatibility across Rust, Python, Node.js, and Go

2. Sign Markdown in place for review

Use JACS when a README, design doc, policy, or release note needs visible content and verifiable sign-off in the same file.

Start with:

Inline Text Signatures

JACS_CONFIG=./reviewer-a.config.json jacs sign-text DESIGN.md
JACS_CONFIG=./reviewer-b.config.json jacs sign-text DESIGN.md
jacs verify-text DESIGN.md

What JACS adds:

A readable signature block appended at the end
Multi-signer review without sidecar JSON
Permissive or strict verification modes

3. Embed provenance in images

Use JACS when a photo, chart, screenshot, or AI-generated image needs verifiable signer identity without a separate metadata file.

Start with:

Image and Media Signatures

jacs sign-image photo.png --out signed.png
jacs verify-image signed.png
jacs extract-media-signature signed.png

What JACS adds:

Embedded PNG iTXt, JPEG APP11, or WebP XMP signatures
Pixel-content integrity checks
Optional robust mode for PNG/JPEG metadata-strip threat models

4. Sign email with Rust

Use JACS when raw RFC 5322 email needs a verifiable signature attachment and field-level content verification.

Start with:

Email Signing and Verification

What JACS adds:

jacs-signature.json MIME attachment
Header, body, and attachment hashes
Forwarding chains through parent signature hashes

Email signing is currently documented as a Rust core API via jacs::email, not as a CLI or Python/Node/Go binding surface.

5. Secure a local MCP tool server

Use JACS when an MCP client is calling tools that should not run on blind trust.

Start with:

MCP Overview

cargo install jacs-cli
jacs mcp

What JACS adds:

A ready-made stdio MCP server
Signing and verification tools for documents, text, images, trust, audit, and agent workflows
Local private-key custody; no HTTP listener

6. Add provenance to framework boundaries

Use JACS when an existing app already has a boundary such as LangChain tool output, FastAPI response, Express middleware, or Koa middleware.

Start with:

What JACS adds:

Signed tool results and responses
Optional strict verification at adapter boundaries
Minimal changes to existing framework code

7. Exchange artifacts across agents or organizations

Use JACS when one agent produces work that another agent, service, or organization must verify before acting on it.

Start with:

What JACS adds:

Signed A2A artifacts
Trust policies for admission control
M-of-N approvals with quorum and algorithm constraints

8. Publish identity without a central auth service

Use JACS when external systems need to verify an agent identity without putting a shared server in the middle.

Start with:

What JACS adds:

Public key fingerprint anchoring
Local trust-store workflows
Local private-key custody

9. Add hosted verification with HAI.AI

Use HumanAssisted/haiai when you want platform workflows for verified documents, agent behavior, benchmarks, and hosted JACS identity flows.

JACS remains the local open source signing and verification layer. HAI.AI is the hosted platform path around those identities and artifacts.

JACS Usage Documentation