UmbraSet – Educational Bitcoin CoinJoin Documentation & Non-Custodial Implementa

[BogdanO]

Hello everyone,

I'd like to introduce UmbraSet, a project focused on making Bitcoin CoinJoin easier to understand through both comprehensive documentation and a hands-on implementation.


Documentation

https://docs.umbraset.com

The documentation explains:

• How CoinJoin works
• Privacy concepts and limitations
• The transaction flow
• How to use the implementation

Interactive Application

https://app.umbraset.com

The application defaults to Bitcoin Testnet, allowing anyone to perform CoinJoin transactions completely free using testnet coins.

The objective is to let users understand CoinJoin by actually using it instead of only reading about it.

It can also be switched to Bitcoin Mainnet for real transactions.


Features

• 100% non-custodial (you always control your own keys and funds)
• Free Bitcoin Testnet environment for learning and experimentation
• Optional Bitcoin Mainnet support
• Small coordinator fee on Mainnet to cover operating costs
• Comprehensive educational documentation
• Built-in feedback and bug reporting system

Why I built UmbraSet

Many CoinJoin resources explain the theory, but relatively few let people safely experience the protocol themselves.

UmbraSet was built to bridge that gap by combining educational documentation with a working implementation that anyone can try on Testnet before deciding whether to use Mainnet.


Feedback Welcome

I'd really appreciate feedback from the Bitcointalk community, especially regarding:

• Technical accuracy
• Privacy and security considerations
• User experience
• Documentation quality
• Ideas for future improvements

Constructive criticism is very welcome. If you find bugs, inaccuracies, or have suggestions, I'd be happy to discuss them.

Thank you for taking the time to check it out.

[BogdanO]

Update: the offline signer is now open source

The one component that touches your private key — the tool you use to sign your CoinJoin inputs — is now public:

https://github.com/CoinJoinHub/offlinesigner

• Reproducible builds — rebuilt twice, independently, in CI on every push, diffing the checksum
• Every release is signed (checksum + detached GPG signature + published key fingerprint)
• Your key never leaves your machine — only the signed transaction (+ account id) is ever uploaded

See Verifying a release in the docs if you want to check the signature yourself before trusting a build.

Feedback and PRs welcome, as always.

[BogdanO]

Update: developer API + interactive docs (Swagger UI)

For anyone who wants to script against UmbraSet instead of clicking through the web UI — there's now a bearer-key REST API covering the full transaction lifecycle:

• Create / update / submit / withdraw a CoinJoin transaction
• List your transactions, filter by status
• Look up any transaction by txid (mempool/confirmed status, spendability)
• Manage your own API keys from the account page — mint, one-time reveal, revoke

Same rules as the web app: non-custodial, testnet or mainnet (a key is scoped to one network when you create it), and rows created through the API show up in the normal web UI and vice versa — it's the same account, same data, just a second way in.

Interactive docs (browse and try every endpoint right from the browser, no key needed just to read the spec):
https://app.umbraset.com/swagger-ui.html

Manage keys here (login required):
https://app.umbraset.com/account/api-keys

As always — this is still an educational project and I'd rather hear "this endpoint is confusing" or "this response leaks more than it should" now than later. Testnet keys cost nothing to mint, so that's the easiest way to kick the tires.