change: Simplify cross chain public key usage (#1057)

Author: AmbientTea

Cargo.lock

@@ -26,6 +26,11 @@ session in order to make `pallet_session` use authorities with less delay.
 ## Added
 
 * Added `partner-chains-node smart-contracts upsert-script` command for inserting and updating versioned scripts.
+* `cross_chain_app` module in `sidechain_domain`, implementing the cross-chain key
+types using Substrate's `app_crypto` macro. This should be a drop-in replacement
+for the analogous cross-chain key types that previously had to be defined by each
+Partner Chain separately for use in `pallet_session_validator_management` and
+other pallets that use cross-chain keys.
 
 # v1.8.0
 

changelog.md

@@ -74,7 +74,7 @@ sp-sidechain = { workspace = true }
 pallet-sidechain = { workspace = true }
 pallet-session-validator-management = { workspace = true }
 sp-session-validator-management = { workspace = true, features = ["serde"] }
-sidechain-domain = { workspace = true, features = ["serde"] }
+sidechain-domain = { workspace = true, features = ["serde", "app-crypto"] }
 sidechain-slots = { workspace = true }
 pallet-address-associations = { workspace = true }
 pallet-block-producer-metadata = { workspace = true }

demo/runtime/Cargo.toml

@@ -111,54 +111,6 @@ pub mod opaque {
 	/// Opaque block identifier type.
 	pub type BlockId = generic::BlockId<Block>;
 
-	pub const CROSS_CHAIN: KeyTypeId = KeyTypeId(*b"crch");
-	pub struct CrossChainRuntimeAppPublic;
-
-	pub mod cross_chain_app {
-		use super::CROSS_CHAIN;
-		use parity_scale_codec::MaxEncodedLen;
-		use sidechain_domain::SidechainPublicKey;
-		use sp_core::crypto::AccountId32;
-		use sp_runtime::MultiSigner;
-		use sp_runtime::app_crypto::{app_crypto, ecdsa};
-		use sp_runtime::traits::IdentifyAccount;
-		use sp_std::vec::Vec;
-
-		app_crypto!(ecdsa, CROSS_CHAIN);
-		impl MaxEncodedLen for Signature {
-			fn max_encoded_len() -> usize {
-				ecdsa::Signature::max_encoded_len()
-			}
-		}
-
-		impl From<Signature> for Vec<u8> {
-			fn from(value: Signature) -> Self {
-				value.into_inner().0.to_vec()
-			}
-		}
-
-		impl From<Public> for AccountId32 {
-			fn from(value: Public) -> Self {
-				MultiSigner::from(ecdsa::Public::from(value)).into_account()
-			}
-		}
-
-		impl From<Public> for Vec<u8> {
-			fn from(value: Public) -> Self {
-				value.into_inner().0.to_vec()
-			}
-		}
-
-		impl TryFrom<SidechainPublicKey> for Public {
-			type Error = SidechainPublicKey;
-			fn try_from(pubkey: SidechainPublicKey) -> Result<Self, Self::Error> {
-				let cross_chain_public_key =
-					Public::try_from(pubkey.0.as_slice()).map_err(|_| pubkey)?;
-				Ok(cross_chain_public_key)
-			}
-		}
-	}
-
 	impl_opaque_keys! {
 		#[derive(MaxEncodedLen, PartialOrd, Ord)]
 		pub struct SessionKeys {
@@ -181,7 +133,7 @@ pub mod opaque {
 	}
 }
 
-pub type CrossChainPublic = opaque::cross_chain_app::Public;
+pub type CrossChainPublic = sidechain_domain::cross_chain_app::Public;
 
 // To learn more about runtime versioning, see:
 // https://docs.substrate.io/main-docs/build/upgrade#runtime-versioning
@@ -400,7 +352,7 @@ impl pallet_session_validator_management::Config for Runtime {
 		input: AuthoritySelectionInputs,
 		sidechain_epoch: ScEpochNumber,
 	) -> Option<BoundedVec<Self::CommitteeMember, Self::MaxValidators>> {
-		select_authorities::<opaque::cross_chain_app::Public, SessionKeys, MaxValidators>(
+		select_authorities::<sidechain_domain::cross_chain_app::Public, SessionKeys, MaxValidators>(
 			Sidechain::genesis_utxo(),
 			input,
 			sidechain_epoch,

demo/runtime/src/lib.rs

@@ -93,20 +93,6 @@
 //! }
 //! ```
 //!
-//! In addition to the session keys, the runtime needs to define an ECDSA key type to represent
-//! the `cross-chain key`:
-//! ```rust
-//! pub mod cross_chain_app {
-//!     use sp_runtime::KeyTypeId;
-//!     use sp_runtime::app_crypto::{ app_crypto, ecdsa };
-//!     pub const CROSS_CHAIN: KeyTypeId = KeyTypeId(*b"crch");
-//! 	app_crypto!(ecdsa, CROSS_CHAIN);
-//! }
-//! pub type CrossChainPublic = cross_chain_app::Public;
-//! ```
-//!
-//! This key serves as the identity of a Partner Chain user across all chains in the ecosystem.
-//!
 //! ### Adding the pallet
 //!
 //! The pallet should be added to the runtime _before_ `pallet_session`, but after the consensus
@@ -140,6 +126,8 @@
 //! defined by other crates and in previous steps:
 //!
 //! ```rust, ignore
+//! use sidechain_domain::cross_chain_app::Public as CrossChainPublic;
+//!
 //! impl pallet_session_validator_management::Config for Runtime {
 //! 	type MaxValidators = MaxValidators;
 //! 	type AuthorityId = CrossChainPublic;

toolkit/committee-selection/pallet/src/lib.rs

@@ -34,6 +34,7 @@ secp256k1 = { workspace = true, features = ["hashes", "alloc"] }
 ed25519-zebra = { workspace = true, optional = true }
 k256 = { workspace = true }
 derive-where = { workspace = true }
+sp-runtime = { workspace = true, optional = true }
 
 [dev-dependencies]
 serde_json = { workspace = true }
@@ -55,5 +56,7 @@ std = [
 	"secp256k1/global-context",
 	"ed25519-zebra",
 	"ed25519-zebra/std",
+	"sp-runtime?/std",
 ]
 serde = ["dep:serde", "scale-info/serde", "sp-core/serde"]
+app-crypto = ["dep:sp-runtime"]

toolkit/sidechain/domain/Cargo.toml

@@ -0,0 +1,45 @@
+//! Substrate key pair types for Partner Chain cross-chain keys
+
+use crate::SidechainPublicKey;
+use parity_scale_codec::MaxEncodedLen;
+use sp_core::crypto::AccountId32;
+use sp_runtime::app_crypto::{app_crypto, ecdsa};
+use sp_runtime::traits::IdentifyAccount;
+use sp_runtime::{KeyTypeId, MultiSigner};
+use sp_std::vec::Vec;
+
+/// Key type for the cross-chain keys
+pub const KEY_TYPE_ID: KeyTypeId = KeyTypeId(*b"crch");
+
+app_crypto!(ecdsa, KEY_TYPE_ID);
+
+impl MaxEncodedLen for Signature {
+	fn max_encoded_len() -> usize {
+		ecdsa::Signature::max_encoded_len()
+	}
+}
+
+impl From<Signature> for Vec<u8> {
+	fn from(value: Signature) -> Self {
+		value.into_inner().0.to_vec()
+	}
+}
+
+impl From<Public> for AccountId32 {
+	fn from(value: Public) -> Self {
+		MultiSigner::from(ecdsa::Public::from(value)).into_account()
+	}
+}
+
+impl From<Public> for Vec<u8> {
+	fn from(value: Public) -> Self {
+		value.into_inner().0.to_vec()
+	}
+}
+
+impl TryFrom<SidechainPublicKey> for Public {
+	type Error = SidechainPublicKey;
+	fn try_from(pubkey: SidechainPublicKey) -> Result<Self, Self::Error> {
+		Public::try_from(pubkey.0.as_slice()).map_err(|_| pubkey)
+	}
+}

toolkit/sidechain/domain/src/cross_chain_app.rs

@@ -6,6 +6,8 @@
 #![deny(missing_docs)]
 
 pub mod byte_string;
+#[cfg(feature = "app-crypto")]
+pub mod cross_chain_app;
 pub mod crypto;
 pub mod mainchain_epoch;