Blockstream dreams up a whole new type of multisig called ROAST

The research unit of Bitcoin (BTC)-focused blockchain tech firm Blockstream has published a proposal for a new type of multisig standard called Robust Asynchronous Schnorr Threshold Signatures (ROAST).

It hopes to avoid the problem of transaction failures due to absent or even malicious signers and can work at scale.

The term multisig or multisignature, refers to a method of transaction in which two or more signatures are required to sign off before it can be executed. The standard is widely adopted in crypto.

According to a May 25 blog post from Blockstream research, the basic idea of ROAST is to make transactions between the Bitcoin network and Blockstream’s sidechain Liquid more efficient, automated, secure and private.

In particular, ROAST has been posited as a signature standard that could work with, and improve, threshold signature schemes such as FROST (Flexible Round-Optimized Schnorr Threshold Signatures):

“ROAST is a simple wrapper around threshold signature schemes like FROST. It guarantees that a quorum of honest signers, e.g., the Liquid functionaries, can always obtain a valid signature even in the presence of disruptive signers when network connections have arbitrarily high latency.”

The researchers highlighted that while FROST can be an effective method for signing off on BTC transactions, its structure of coordinators and signers is designed to abort transactions in the presence of absent signers, making it secure but suboptimal for “automated signing software.”

To solve this problem, the researchers say that ROAST can guarantee enough reliable signers on each transaction to avoid any failures,and it can be done at a scale much larger than the 11-of-15 multisig standard that Blockstream primarily utilizes.

“Our empirical performance evaluation shows that ROAST scales well to large signer groups, e.g., a 67-of-100 setup with the coordinator and signers on different continents,” the post reads, adding that:

“Even with 33 malicious…