The research unit of the blockchain technology company focused on Bitcoin (BTC) Blockstream has published a proposal for a new type of multisignature or 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 transaction method in which two or more signatures are required for it to be executed.. The standard is widely adopted in the crypto space.
According to a Wednesday post on the Blockstream research blog, the basic idea of ROAST is to make transactions between the Bitcoin network and the Blockstream Liquid sidechain more efficient, automated, secure and private.
In particular, ROAST has been postulated as a signature standard that could work with, and improve upon, threshold signature schemes such as Flexible Round-Optimized Schnorr Threshold Signatures (FROST):
“ROAST is a simple wrapper of threshold signature schemes like FROST. It ensures that a quorum of honest signers, for example Liquid officials, can always obtain a valid signature even in the presence of rogue signers when network connections have arbitrarily high latency.”
The researchers highlighted that while FROST can be an efficient method of signing BTC transactions, its coordinator and signer structure 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 claim that ROAST can guarantee enough trusted signers in each transaction to avoid any failure. Also, it can be carried out at a much larger scale than the 11 of 15 multisig standard that Blockstream primarily uses..
“Our empirical performance evaluation shows that ROAST is well suited to large groups of signers, for example a 67 of 100 setup with the coordinator and signers on different continents,” the post reads.adding that:
“Even if 33 malicious signers try to block signature attempts (for example, by sending invalid responses or not responding at all), all 67 honest signers can successfully produce a signature in a few seconds.”
To give a simple explanation of how ROAST works, the team used an analogy of a democratic council responsible for Frostland legislation..
Basically, the argument being that it can be tricky to get legislation (transactions) signed in Frostland, as there are a myriad of factors at any given time that can make most council members unavailable or absent.
One procedure (ROAST) to counteract this is for the council secretary to compile and maintain a large enough list of supporting council members (signatories) at any given time.so that there are always enough members for legislation to pass:
“If at least seven council members really support the bill and behave honestly, at any point, he knows these seven members will end up signing their currently assigned copy and being added back to the clerk’s list.”
“A) Yes, the secretary can always be sure that seven members will be back on his list at some point in the future, and thus the signing procedure will not get bogged down,” the post adds.
ROAST is part of a collaboration between Blockstream researchers Tim Ruffing and Elliott Jin, Viktoria Ronge and Dominique Schröder of the University of Erlangen-Nuremberg, and Jonas Schneider-Bensch of the Helmholtz Center for Information Security CISPA..
Along with the blog post, the researchers also linked to a 13-page research paper that provides a more detailed summary of ROAST.
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