We believe it is important to acknowledge the work which has led up to the current Fedimint opensource protocol design.

We are currently aware of the following efforts to build federated eCash mints:

• Fedimint: A modular federated eCash prototype still under heavy development written in Rust. It already supports all main operations (deposit/withdraw via both on-chain Bitcoin and Lightning, eCash transfers) and comes with a rudimentary CLI client. Some features are still missing and blocking mainnet deployments, but the project is moving quickly. If you are interested in contributing check out the GitHub repository.
• SCRIT1: A half-finished implementation of a federated chaumian mint written in Go, developed by Frank Braun and Jonathan Logan. It does not implement BTC backing, but was the first public implementation.
• SCRIT2: A reimplementation of a federated chaumian mint written in Go, supporting multiple currencies, inter-currency swap transactions, receiver- and sender-initiated half-offline transactions as well as complex multiparty transactions. It is in private beta and has no direct linkage with bitcoin yet. You can read more on Jonathan’s blog.
• Open Transactions: Open Transactions also deserves a honorable mention since it already allowed for the issuance of eCash tokens backed by Bitcoin held in a multisig wallet. It does not appear to support threshold issuance of eCash tokens though.