Transports

Transports

A transport is the noticeboard that carries identity-signed offers and forwards encrypted coordination blobs between counterparties. It never matches, executes, custodies, or charges — operators see ciphertext only. Satchel speaks two transports side by side, and you and a counterparty need just one board in common.

For the wire-level details see the Pact handbook transport chapters: https://github.com/PoC-Consortium/satchel/tree/master/docs/handbook-pact.

Nostr vs Corkboard at a glance

	Nostr	Corkboard
Role	Default transport	Alternative, self-hostable
Infrastructure	Nothing to run	Run an HTTP board
Default	6 prewired relays (in Satchel)	127.0.0.1:9780
Posting	Fans out across all configured relays	One HTTP board
Style	Censorship-resistant, public relays	Bisq-style, community-operated

Nostr (the default)

Satchel ships with six recommended relays prewired on a fresh install, so there is nothing to host — post and go. Offers map to Nostr events:

• Public offers are addressable events of kind 31510 (NIP-33), signed by your identity key (identity == npub).
• Coordination messages are gift-wrapped, kind 1059 (NIP-59), authored by a fresh ephemeral key so the sender is hidden.
• Offers carry a rolling NIP-40 expiry: min(now + 1800s, created + ttl_secs) — not a flat ttl_secs.

Note — the engine's --nostr-relay defaults empty; the default relay list lives in Satchel. Saving an empty relay list disables Nostr.

Corkboard (self-hostable)

Corkboard is a single small HTTP+SQLite binary a community can run for its own noticeboard. Default listen address 127.0.0.1:9780. Point pactd at it with --board-url, or add it in Satchel under Settings → Network. See Self-Hosting a Corkboard.

Both are blind

Whichever transport you use, the privacy model is the same:

• Offers are public but signed — anyone can read terms, nobody can forge them.
• Coordination travels as sealed PACTSEALED1 blobs — encrypted to the recipient, so the board/relay only ever sees ciphertext. There is no plaintext downgrade.
• Relays can withhold, delay, or drop messages, but your funds are protected by timelocks, not by trusting the relay. Mitigate liveness risk by using multiple boards and refreshing offers.

Boards and relays are independent, equal noticeboards — a post fans out across all of them at once, while browsing selects one board at a time.

See also

• Self-Hosting a Corkboard · Private Offers · Satchel User Guide