Add and Remove parties #17

tudorcebere · 2021-09-09T19:16:45Z

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elichai · 2021-09-12T16:07:26Z

Hi!
Thanks for contributing :)
The new simulate_dkr_add test seem to fail:

thread 'test::tests::simulate_dkr_add' panicked at 'called `Result::unwrap()` on an `Err` value: FairnessProof', src/test.rs:160:10

EDIT: I see that that's because collect_new_party always returns an error

src/lib.rs

src/test.rs

elichai · 2021-09-13T14:42:49Z

Another thing, IIUC the approach you talk is as follows:
t parties calculate their additive shares, they then do PVSS with the additive share in f_i(0)(such that f(0)=Σshareᵢ) and they generate n+1 that everyone sums up.
this requires all n parties to be online to recieve their points, sum them, and verify the commitments.

Instead we could do the following:

Notation: πᵢ(x) is the polynomial representing the Lagrange Coefficient required for interpolation ((x-x₁)(x-x₂)/(x₁-x₂)(x₁-x₃)....)

So t parties come together, and they calculate:
vᵢ = πᵢ(n+1)*yᵢ
Then use SSS and generate polynomials gᵢ(x) with gᵢ(0) = vᵢ, and use PVSS to compute together a polynomial g(x) of degree t-1 where g(0)=Σvᵢ.
Then each party encrypts their point using P_n+1's paillier key and broadcast it, Which then decrypts them and interpolates g(0) to find their point.
Now party n+1 has the point f(n+1) and no party needs to modify their own secret.
(note that P_n+1 will need to check that against the commitments of the PVSS etc. to make sure their not being lied to)

tudorcebere · 2021-09-20T13:07:24Z

I need to take this on paper, if you have any links to check on this, it would be very useful!

src/lib.rs

src/test.rs

src/add_party.rs

elichai · 2021-10-20T09:10:33Z

src/add_party.rs

+impl JoinMessage {
+    pub fn distribute() -> (Self, Keys) {
+        let new_party_key = Keys::create(0);
+        let (dlog_statement, composite_dlog_proof) = generate_dlog_statement();


I'm confused, this is generating a proof for some random paillier key that isn't saved?

Yes, @omershlo explained it in the telegram conversation. It confuses me as well, but I understood that it's like system parameters that are submitted, we don't care about the secret at all.

src/add_party.rs

elichai · 2021-10-20T12:41:09Z

src/add_party.rs

+        for refresh_message in refresh_messages.iter() {
+            if refresh_message.public_key != refresh_messages[0].public_key {
+                return Err(FsDkrError::BroadcastedPublicKeyError);
+            }
+        }


Are the parties signed on this or something? how do you know they actually sent that? (as I think the whole point is that we do not require secure channels)

For the key to be generated, all other parties need to validate the same public key. I know that @omershlo mentioned that we should be able to verify everything in the message, but for now, this is good enough and we can continue working on it.

src/refresh_message.rs

src/add_party.rs

omershlo · 2021-10-20T13:49:27Z

src/add_party.rs

+        ni: h2,
+    };
+
+    let composite_dlog_proof = CompositeDLogProof::prove(&statement, &xhi);


we need two composite dlog proofs here. copy from here: https://github.com/ZenGo-X/multi-party-ecdsa/blob/master/src/protocols/multi_party_ecdsa/gg_2020/party_i.rs#L232-L246

I believe that both proofs and statements needs to be attached and verified, but which of them we use in the h1_h2_N_tilde_vec? The one with the base in h1, right? I've implemented this, tell me if it's fine.

src/test.rs

tudorcebere added 3 commits September 9, 2021 22:04

initial work on add

40ba3a4

Need to finish new_party_collect

bab2704

small fix

38fd6d2

tudorcebere changed the title ~~Add parties~~ [WIP] Add parties Sep 9, 2021

Indexes -> Indices

a14eeca

omershlo requested a review from elichai September 9, 2021 19:25

elichai reviewed Sep 13, 2021

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tudorcebere added 4 commits September 24, 2021 19:17

small fixes

1e6956e

refactor a few ideas

edae024

making the fairness proof cleaner

d0e9b70

small fix

9efa467

elichai reviewed Oct 8, 2021

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tudorcebere added 4 commits October 8, 2021 13:55

Add the party to the map. Thank you Elichai for finding the bug

0e07828

adding dlog statement

bcd9be7

Adding dlog statement

89d4032

replace implementation

f85a079

tudorcebere changed the title ~~[WIP] Add parties~~ Add parties Oct 18, 2021

omershlo reviewed Oct 20, 2021

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elichai reviewed Oct 20, 2021

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omershlo reviewed Oct 20, 2021

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omershlo reviewed Oct 20, 2021

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tudorcebere added 3 commits October 20, 2021 22:51

Cleaning up and adding the dlog proof in base h2.

5c710a0

Adding comments and cleanup on the replace test

0894a9b

Documentation on adding a party

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omershlo reviewed Oct 22, 2021

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elichai changed the title ~~Add parties~~ Add and Remove parties Nov 1, 2021

elichai merged commit dc7e937 into ZenGo-X:main Nov 1, 2021

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Add and Remove parties #17

Add and Remove parties #17

tudorcebere commented Sep 9, 2021

elichai commented Sep 12, 2021 •

edited

elichai commented Sep 13, 2021 •

edited

tudorcebere commented Sep 20, 2021

elichai Oct 20, 2021

tudorcebere Oct 20, 2021

elichai Oct 20, 2021

tudorcebere Oct 20, 2021

omershlo Oct 20, 2021

tudorcebere Oct 20, 2021

Add and Remove parties #17

Add and Remove parties #17

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tudorcebere commented Sep 9, 2021

elichai commented Sep 12, 2021 • edited

elichai commented Sep 13, 2021 • edited

tudorcebere commented Sep 20, 2021

elichai Oct 20, 2021

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elichai commented Sep 12, 2021 •

edited

elichai commented Sep 13, 2021 •

edited