Could you please confirm if binance-tsslib supports strict 3/3 threshold signatures?

[BillInUK]

I am currently looking to implement a strict 3/3 threshold signature scheme, where all three private key shares are required simultaneously for signing and private key recovery. Is it possible to achieve this?

[ahsan-arif]

Signature requires T+1 threshold, you will set TOTAL =3 and THRESHOLD = 2 in params to achieve a strict 3/3 threshold.

params := tss.NewParameters(curve, ctx, thisParty, TOTAL, THRESHOLD)

[BillInUK]

Hi, following up on the previous answer:
If I set TOTAL = 3 and THRESHOLD = 2, and I give two private key shares to another party while keeping one share myself, would that allow the other party to:

Reconstruct the full private key?

Sign transactions using only the two shares they hold, without my share?

I want to ensure that in a strict 3/3 setting, all three shares must be present for signing or key recovery. Could you clarify whether the THRESHOLD = 2 configuration still enforces this requirement?

Thanks for your help!

[ahsan-arif]

I can’t yet confirm whether key rotation will work, as I’m currently blocked on it and have an open issue. I did test a scenario with a threshold of 2, where 2 out of 3 parties attempt to sign a message. In this case, the signature does not complete because the initiator waits for a response from the third party. If that party fails to participate, the request eventually times out. I can demonstrate this as well if you are willing to hop on a call.

[BillInUK]

Thank you for your warm help. It's a pity that my English isn't good enough to communicate verbally with you. If you later confirm the issue I mentioned, I hope you can provide feedback to me. Thanks again.

[ahsan-arif]

As I have said earlier, you can achieve a strict 3/3 threshold by setting the PARTIES = 3 and THRESHOLD to 2 because tss-lib expects t+1 parties to sign a message. As far as key rotation is concerned, I am currently working on it and believe that THRESHOLD=2 might require only 2 parties to be present for key rotation; one of the tss-lib developers can confirm this.

[BillInUK]

thanks, have you confirmed this issue with the developers from Binance?

If the tsslib is set to 3/3 during the keygen phase, does the resharing phase only require 2 participants to recover?

[ahsan-arif]

I also have an open issue; it turns out they are either very busy or don't care about the open issues at all.