A signing scheme that can be verified by anyone from the group who signed jointly

weixin0129

7/1/23, 7:28 AM

Suppose that a set of entities each have public/private key pairs, (P1, S1), (P2, S2), ..., (Pn, Sn).

In a straightforward scenario, a message signed with Si can be verified using Pi.

My question is, is there a way for me to sign a message with {S1...Sn} and the signature can be verified using one of the {P1...Pn}?

Here is my use case:

I have a list of clients, with each I share a key pair with.

In most of the cases the communication is 1 to 1 - I sign a message dedicated to one client with the dedicated private key and the client can verify using the corresponding public key.

For a new use case, I want to achieve a 1 to n communication without signing the message n times - I want to see if it's possible to create one signature that can be verified by the n clients using their respective public key.

0 + 0

signature

knaccc

7/1/23, 11:38 AM

A signature proves someone knows a secret which is linked to a corresponding public key. If there is no link between the secret and any of the other public keys, then there is no way that someone attempting to verify the signature with an independent public key can know if the correct secret has been used in the signature. Perhaps if you could elaborate more on your scenario, there might be an interesting approach to solving the problem you have by generating the other public keys such that they are linked to the secret.

weixin0129

7/1/23, 5:20 PM

Thanks @knaccc for your response! I edited my question to add my use case. Please let me know if it helps clarify my question.

knaccc

7/1/23, 7:03 PM

I looked at your updated question. I'm not entirely sure what you mean by "I have a list of clients, with each I share a key pair with". What is wrong with you just having one (private, public) key pair, and using that to sign all of your outgoing messages? You just tell everyone your public key. They also have their own personal key pairs that they will only use for signing messages on their own behalf to send to you.

weixin0129

7/16/23, 6:33 PM

Sorry for the terribly delayed response to your question. Yes I would have used a common key pair if i could. But I wonder if there is a way that does not require creating and distributing new keys - so that it's a seamless experience to the clients, i.e. they can verify the signatures like how they used to without knowing the signing has changed on my side. Please let me know if that makes sense. And thanks for your help. @knaccc

knaccc

7/16/23, 7:55 PM

So your question is simply: I use a key pair to sign messages to send to other people. Is there a way to change my public key without having to advise each of those people individually of my new public key?

weixin0129

7/16/23, 9:20 PM

Either a new key that's somehow associated with all the existing keys, or a signing mechanism that involves all existing keys.

weixin0129

7/16/23, 9:23 PM

but pretty much, yes. The goal is to only create the signature once instead of signing it using different keys multiple times.

knaccc

7/17/23, 1:26 AM

When you next send a signed message to someone, you can simply sign it with your brand-new public key, and also send at the same time your brand-new public key signed by your older private key(s). This means someone can check that this brand-new key pair you are using has been authorized by the older key pairs you were using.

Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: A signing scheme that can be verified by anyone from the group who signed jointly

TH: แผนการลงนามที่ใครก็ตามจากกลุ่มที่ลงนามร่วมกันสามารถตรวจสอบได้

RO: O schemă de semnare care poate fi verificată de oricine din grupul care a semnat împreună

RU: Схема подписи, которую может проверить любой из группы, подписавшей совместно

VI: Sơ đồ ký có thể được xác minh bởi bất kỳ ai trong nhóm đã cùng ký

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