bidirectional: hydration indexer by ppca · Pull Request #621 · sig-net/mpc

ppca · 2025-12-11T11:19:22Z

This works locally with https://github.com/galacticcouncil/hydration-node/pull/1189/files.

https://github.com/galacticcouncil/hydration-node/pull/1189/files has been closed, and hydration team is pushing forward with https://github.com/galacticcouncil/hydration-node/pull/1235/files#.

We can review this PR first, and I'll push new PR that aims to dynamically work with hydration runtime changes, i.e. https://github.com/galacticcouncil/hydration-node/pull/1235/files#.

Copilot

Pull request overview

This PR adds support for the Hydration blockchain as a new chain indexer, following the established patterns from Ethereum and Solana indexers. The implementation includes bidirectional transaction support and creates a common indexer module to reduce code duplication across chain implementations.

Key Changes

Adds indexer_hydration module with Merkle-proof verified event indexing from Hydration blockchain
Creates indexer_common module to consolidate shared indexer logic across Solana, Ethereum, and Hydration
Extends the Chain enum and related infrastructure to support Hydration chain

Reviewed changes

Copilot reviewed 17 out of 19 changed files in this pull request and generated 9 comments.

Show a summary per file

File	Description
`chain-signatures/node/src/indexer_hydration/mod.rs`	New Hydration indexer implementation with event processing and Merkle proof verification
`chain-signatures/node/src/indexer_common.rs`	New shared indexer functionality extracted from Solana indexer
`chain-signatures/node/src/indexer_sol.rs`	Refactored to use common indexer functions
`chain-signatures/node/src/indexer_eth/mod.rs`	Refactored to use common backlog recovery
`chain-signatures/node/src/rpc.rs`	Added Hydration client and publish support
`chain-signatures/node/src/cli.rs`	Added Hydration CLI arguments
`chain-signatures/primitives/src/lib.rs`	Extended Chain enum with Hydration
`chain-signatures/crypto/src/kdf.rs`	Added Hydration epsilon derivation
`integration-tests/src/*.rs`	Updated integration test configuration
`chain-signatures/node/Cargo.toml`	Added Substrate/Polkadot dependencies

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chain-signatures/node/src/indexer_hydration/mod.rs

chain-signatures/node/src/indexer_common.rs

chain-signatures/node/src/indexer_hydration/mod.rs

chain-signatures/node/src/indexer_common.rs

Copilot

Pull request overview

Copilot reviewed 18 out of 20 changed files in this pull request and generated 5 comments.

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chain-signatures/node/src/indexer_hydration/mod.rs

chain-signatures/node/src/indexer_common.rs

Copilot

Pull request overview

Copilot reviewed 20 out of 23 changed files in this pull request and generated no new comments.

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volovyks

Great work! I have not found any major issues, let's move forward with this.

volovyks · 2025-12-15T18:54:37Z

chain-signatures/crypto/src/kdf.rs

            Chain::Ethereum => "0x1",
            Chain::Solana => "0x800001f5",
            Chain::Bitcoin => "bip122:000000000019d6689c085ae165831e93",
+            Chain::Hydration => "polkadot:2034",


2034 is not a CAIP-2 identifier, it's a ParaId that identifies it inside of Polkadot network.
CAIP 2 is using the genesis hash. OS it should be polkadot:afdc188f45c71dacbaa0b62e16a91f72.

this is matching the id that galacticcouncil/hydration-node#1275 sets in the tests.

Then we need to change it there @esaminu and fix here

volovyks · 2025-12-15T19:07:41Z

infra/scripts/generate_keys/src/main.rs

 fn main() {
    let args: Vec<String> = env::args().collect();

+    let (hydration_pair, hydration_phrase, _seed) = sr25519::Pair::generate_with_phrase(None);


The whole /infra folder is intended to be removed (#560). Let's added changes there. @auto-mausx please, approve that PR if we are ready to move forward with it.

volovyks · 2025-12-15T19:17:02Z

chain-signatures/primitives/src/lib.rs

            Chain::NEAR => return None,
            Chain::Ethereum => ("CHECKPOINT_INTERVAL_ETHEREUM", 20),
            Chain::Solana => ("CHECKPOINT_INTERVAL_SOLANA", 120),
+            Chain::Hydration => ("CHECKPOINT_INTERVAL_HYDRATION", 120),


@ChaoticTempest remind me please, why Ethereum has smaller backup interval compared to Solana and now Hydration?

I think it's because the Ethereum block time is slower. It's better if checkpoints are never too old.

Maybe for Hydration it should be larger than for Solana?

If Ethereum block time is slower, why do we need to back it up more often?

chain-signatures/node/src/rpc.rs

chain-signatures/node/src/respond_bidirectional.rs

volovyks · 2025-12-15T20:17:28Z

chain-signatures/node/src/indexer_sol.rs

        // Call the existing derive_epsilon_sol function with the correct parameters
        // to match the TypeScript implementation
-        let epsilon = derive_epsilon_sol(self.key_version, &self.sender.to_string(), &self.path);
+        let epsilon = derive_epsilon_sol(self.key_version, &self.sender_string(), &self.path);


I would say it should be sender(), not sender_string(). We should not specify type in the function name.

chain-signatures/node/src/indexer_sol.rs

volovyks · 2025-12-15T20:36:50Z

chain-signatures/node/src/indexer_hydration/mod.rs

+
+/// Fetch and *verify* the SCALE‑encoded `System::Events` bytes at a given block.
+///
+/// - Uses `state_get_read_proof` via `LegacyRpcMethods`.


this is for fetching proof, but I haven't been able to test it locally.

I'm saying that this API is marked as legacy (outdated), maybe there is new one that we should use.

chain-signatures/node/src/indexer_hydration/mod.rs

jakmeier

Looking good!

chain-signatures/node/Cargo.toml

chain-signatures/node/src/indexer_common.rs

jakmeier · 2025-12-18T11:23:28Z

chain-signatures/node/src/indexer_common.rs

+    if let Err(err) = sign_tx.send(Sign::Request(sign_request)).await {
+        // TODO: handle error to ensure 100% success rate
+        let chain = sign_event.source_chain();
+        tracing::error!(?err, chain = %chain, "Failed to send {} sign request into queue", chain.as_str());
+    } else {


Hm, so if this fails, we have a full channel buffer. A burst of incoming requests could easily trigger this. So anyone could try and abuser this to prevent a signature from getting through.

But the good news is, at this point we already have the request in the backlog. All we need is to ensure we start new attempts on backlog requests if no success is seen for a time. (cc @ChaoticTempest )

I know this is just moved from other files in this PR. But can we maybe link this to an issue or something to make it less likely this is just buried and forgotten?

jakmeier · 2025-12-18T11:38:42Z

chain-signatures/node/src/indexer_common.rs

+    let target_chain = match target_chain {
+        Ok(chain) => chain,
+        Err(_) => Chain::Ethereum,
+    };


We send to ETH if we don't know where it should go? Why?

That's because now all the bidirectional tx's send actual transaction on Ethereum. This will need to change in the future.

It would be safer to throw an error. I guess we are specifying target_chain=Ethereum anyway.

chain-signatures/node/src/rpc.rs

jakmeier · 2025-12-18T12:49:43Z

chain-signatures/primitives/src/lib.rs

            Chain::NEAR => return None,
            Chain::Ethereum => ("CHECKPOINT_INTERVAL_ETHEREUM", 20),
            Chain::Solana => ("CHECKPOINT_INTERVAL_SOLANA", 120),
+            Chain::Hydration => ("CHECKPOINT_INTERVAL_HYDRATION", 120),


I think it's because the Ethereum block time is slower. It's better if checkpoints are never too old.

Maybe for Hydration it should be larger than for Solana?

* bidirectional: hydration indexer --------- Co-authored-by: Xiangyi Zheng <xyzheng@uhicago.edu>

ppca requested a review from Copilot December 11, 2025 11:32

Copilot started reviewing on behalf of ppca December 11, 2025 11:33 View session

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ppca requested a review from Copilot December 13, 2025 08:03

Copilot started reviewing on behalf of ppca December 13, 2025 08:03 View session

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ppca requested a review from Copilot December 15, 2025 03:11

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ppca marked this pull request as ready for review December 15, 2025 03:17

volovyks requested review from ChaoticTempest, Pessina, esaminu and volovyks December 15, 2025 18:29

volovyks reviewed Dec 15, 2025

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jakmeier previously approved these changes Dec 18, 2025

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Xiangyi Zheng added 10 commits December 19, 2025 09:57

hydration indexer: compiled

064b7ef

add hydration indexer run to cli.rs

b92ac98

minor

683c65e

make run() return nothing

1c3ef35

use same entropy

326f715

use same entropy for sign bidirectional as well

0fff87f

fix all errors except read respond addr match

4aa1358

more refactoring and script to generate hydration signer_uri

3732426

remove unwraps

f214284

address comments and solve merge conflicts

22f9f94

ppca dismissed jakmeier’s stale review via 22f9f94 December 19, 2025 02:23

ppca force-pushed the xiangyi/hydration_indexer branch from 6fe77d6 to 22f9f94 Compare December 19, 2025 02:23

additional changes

676e9e5

auto-mausx approved these changes Dec 19, 2025

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ppca merged commit 3d35002 into develop Dec 19, 2025
3 of 4 checks passed

ppca deleted the xiangyi/hydration_indexer branch December 19, 2025 10:23

ppca added a commit that referenced this pull request Jan 21, 2026

bidirectional: hydration indexer (#621)

291913f

* bidirectional: hydration indexer --------- Co-authored-by: Xiangyi Zheng <xyzheng@uhicago.edu>

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Pull request overview

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ppca commented Dec 11, 2025 •

edited

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