This post outlines the communication requirements for implementing FROST in a point to point communication model, and describe my plans to build a Rust library providing FROST in a such network model. The library will be used to build a decentralised mining solution for bitcoin.


Threshold Signatures in point to point networks enable multiple parties to agree on the state of system at regular intervals. This enables applications where members of the network need to agree on a state and create a joint signature to make progress.

The prime motivation for working on this is to provide a decentralised mining solution. When miners co-ordinate over a P2P network they need to collectively sign bitcoin transactions for paying out all the miners in proportion to the work done by miners. Threshold signatures will allow producing signatures for the transactions. Members will also indirectly agree on the proportion of work done when they agree on the payout amounts for all miners before the sign a bitcoin transaction.

FROST Communication Requirements

To implement FROST both broadcast and one to one communication channels are required. This post highlights these requirements and present the design we follow for building a decentralised mining solution.

Unicast Channels

From section on peer to peer channels

  1. Authenticated
  2. Reliable
  3. Confidential
  4. Unordered

Authentication and Confidentiality are satisfied by using Noise_XX protocol. XX implies both parties transmit their static keys. The XX handshake supports mutual authentication and transmission of static public keys and therefore provides the requirements of Authentication and Confidential channels between any two parties.

Reliability is satisfied by requiring explicit ACKs for messages sent over the point to point channel.

Unordered communication is a relaxation on the requirements and therefore we don’t need to address it further.

Broadcast Channels

From section on broadcast channels

  1. Consistent. Each participant has the same view of the message sent over the channel.
  2. Authenticated. Players know that the message was in fact sent by the claimed sender. In practice, this requirement is often fulfilled by a PKI.
  3. Reliable Delivery. Player $i$ knows that the message it sent was in fact received by the intended participants.
  4. Unordered. The channel does not guarantee ordering of messages.

According to FROST documentation the echo-broadcast protocol is sufficient and we don’t need a byzantine broadcast channel. We therefore provide an implementation of the echo-broadcast protocol on top of point to point noise channels.

With the point to point noise channels on TCP we get Authenticated, Reliable and Ordered broadcast. Consistency is sufficiently satisfied by the echo-broadcast protocol. I will soon write a layman description of echo broadcast in another post.

Implementation Plan

I have started work on the using noise point to point channels and echo-broadcast as a Rust library. With FROST integrated into such a library I will achieve the following two outcomes:

  1. Have practical results on the limits of scaling FROST.
  2. Have a Rust library any application can use.

Previous Work

I wrote a blog post earlier about using FROST for Braidpool and there the broadcast channel didn’t meet the requirements listed above.