PSBTHub: trust-minimized PSBT relay for multisig coordination (OSS)

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When you run multisig, the hardest part often isn’t cryptography — it’s coordination.

People end up moving PSBTs through chat apps, email, cloud drives, AirDrop… and you get:

• version chaos (“which PSBT is the latest?”)
• unnecessary metadata in third-party services
• vendor lock-in (“this wallet only wants to talk to itself”)

So I built PSBTHub: a small PSBT relay for exchanging PSBTs between signers/wallets in a wallet-agnostic and trust-minimized way.

What it is (and what it isn’t)What it is (and what it isn’t)

• It is: a simple layer to move PSBTs between signers (via shareable links).
• It is not: a wallet, a custody service, or a broadcast backend.

How it works (high level)How it works (high level)

1. You upload a PSBT
2. It generates a share link (either key-in-URL-fragment or password mode)
3. The next signer opens it, downloads, decrypts, signs, and passes it along (or sends it back)

Security model (what I care about most)Security model (what I care about most)

The goal is simple: the server must not learn the content.

• Encryption happens client-side (E2E). The server only sees ciphertext.
• The share link can carry part of the secret (URL fragment), or you can use a password.
• There’s a delete capability concept (delete without accounts).

Realistic risks I’m explicitly thinking about (and want feedback on):

• link leakage (clipboard / history / forwarding)
• weak password brute-force
• metadata: time, IP, approximate payload size
• XSS / supply-chain (the usual web reality)

Who it’s forWho it’s for

• multisig power users (Sparrow/Caravan/Specter/Nunchuk, etc.)
• small teams / treasury setups (2-of-3, 3-of-5 approvals)
• families (signers in different locations)

What I’m looking for nowWhat I’m looking for now

I’m a solo builder, so I’m not here to “market” — I want honest feedback from people who actually use PSBTs.

Questions:

1. What metadata is a deal-breaker for you (IP/size/timing), and what’s acceptable?
2. Do you prefer key in URL fragment or password mode (UX vs security)?
3. What’s must-have for a multisig workflow? (TTL, notes, audit trail, templates, etc.)
4. Which wallets / flows would you want to see supported first-class?

If you sign PSBTs a few times a month and want to test it, drop a comment — I’ll share specific scenarios and iterate fast.

Repo:

https://github.com/Asylian21/psbthub.io

“Standards outlive trends. Lock-in is just temporary convenience.”