posta

URL-to-URL messaging with cryptographic origin authentication.

Every participant is a URL. To send Alice a message, you POST to her URL. When her server receives a message claiming to be from Bob, it verifies the signature against the public key Bob publishes at his own URL. No relays, no central directory, no PKI — HTTPS bootstraps the trust.

Quick start

# install
go install <module>/cmd/posta@latest

# first-run setup (interactive: URL, TLS mode, display name)
posta init

# start the daemon (auto-TLS via Let's Encrypt by default)
posta serve

# open the inbox/compose TUI
posta

# one-shot send (for shell pipelines)
echo '{"hello":"world"}' | posta send https://bob.example/inbox

What's in this repo

• A wire protocol, defined in SPEC.md. Implementable in any language with an HTTP client and Ed25519. Test vectors under testdata/vectors/ are part of the spec.
• A reference Go implementation as a single binary: HTTPS daemon, bubbletea TUI, SQLite-backed inbox/outbox.
• Examples under examples/ (Python, JavaScript, Bash) — send and receive in third-party languages, demonstrating the protocol's portability.

Why this exists

If you want to receive a message at https://alice.example/inbox and know with cryptographic certainty that it really came from https://bob.example/inbox, this is the simplest thing that works. No accounts, no shared API keys, no service in the middle.

Design

See CONTEXT.md for the design rationale, vocabulary, and explicit non-goals.

The Go binary is a reference implementation, not the source of truth. Behavior changes require test vector updates. See CLAUDE.md for contributor and AI-agent conventions.

Status

v1 in development.

License

TBD.