srml/authority-discovery: Introduce srml module to sign and verify (#3385)

In order to have authorities (validators) discover each other, they need to publish their public addresses by their ip address on the Kademlia Dht indexed by their public key. This payload needs to be signed by a key identifying them as a valid authority. Code inside `/core` does not know the current set of authorities nor can it assume what kind of cryptography primitives are currently in use. Instead it can retrieve its public key and the current set of authorities from the runtime and have it sign and verify Dht payloads. This commit enables code in `/core` to do so by introducing a srml module and runtime api to: 1. Retrieve own public key. 2. Retrieve public keys of current authority set. 3. Sign a Dht payload. 4. Verify a Dht payload. This commit makes the logic from the previous commit (`core/consensus/common/primitives.ConsensusApi`) cf80af9255 obsolete and thus removes it.
2026-05-01 05:27:56 +00:00 · 2019-08-20 17:39:14 +02:00
parent 5ff10aece8
commit 2c0e73b78c
15 changed files with 509 additions and 69 deletions
@@ -2296,6 +2296,7 @@ dependencies = [
 "rand 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
 "sr-io 2.0.0",
 "sr-primitives 2.0.0",
+ "srml-authority-discovery 0.1.0",
 "srml-balances 2.0.0",
 "srml-contracts 2.0.0",
 "srml-finality-tracker 2.0.0",
@@ -2419,6 +2420,7 @@ dependencies = [
 "sr-staking-primitives 2.0.0",
 "sr-std 2.0.0",
 "sr-version 2.0.0",
+ "srml-authority-discovery 0.1.0",
 "srml-authorship 0.1.0",
 "srml-babe 2.0.0",
 "srml-balances 2.0.0",
@@ -2440,9 +2442,9 @@ dependencies = [
 "srml-system 2.0.0",
 "srml-timestamp 2.0.0",
 "srml-treasury 2.0.0",
+ "substrate-authority-discovery-primitives 2.0.0",
 "substrate-client 2.0.0",
 "substrate-consensus-babe-primitives 2.0.0",
- "substrate-consensus-common-primitives 2.0.0",
 "substrate-keyring 2.0.0",
 "substrate-offchain-primitives 2.0.0",
 "substrate-primitives 2.0.0",
@@ -2503,7 +2505,6 @@ dependencies = [
 "srml-timestamp 2.0.0",
 "substrate-client 2.0.0",
 "substrate-consensus-babe-primitives 2.0.0",
- "substrate-consensus-common-primitives 2.0.0",
 "substrate-offchain-primitives 2.0.0",
 "substrate-primitives 2.0.0",
 "substrate-session 2.0.0",
@@ -3805,6 +3806,23 @@ dependencies = [
 "substrate-primitives 2.0.0",
 ]

+[[package]]
+name = "srml-authority-discovery"
+version = "0.1.0"
+dependencies = [
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.97 (registry+https://github.com/rust-lang/crates.io-index)",
+ "sr-io 2.0.0",
+ "sr-primitives 2.0.0",
+ "sr-std 2.0.0",
+ "srml-im-online 0.1.0",
+ "srml-session 2.0.0",
+ "srml-support 2.0.0",
+ "srml-system 2.0.0",
+ "substrate-application-crypto 2.0.0",
+ "substrate-primitives 2.0.0",
+]
+
 [[package]]
 name = "srml-authorship"
 version = "0.1.0"
@@ -4381,6 +4399,16 @@ dependencies = [
 "substrate-test-runtime-client 2.0.0",
 ]

+[[package]]
+name = "substrate-authority-discovery-primitives"
+version = "2.0.0"
+dependencies = [
+ "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "sr-primitives 2.0.0",
+ "sr-std 2.0.0",
+ "substrate-client 2.0.0",
+]
+
 [[package]]
 name = "substrate-basic-authorship"
 version = "2.0.0"
@@ -4619,16 +4647,6 @@ dependencies = [
 "substrate-test-runtime-client 2.0.0",
 ]

-[[package]]
-name = "substrate-consensus-common-primitives"
-version = "2.0.0"
-dependencies = [
- "parity-scale-codec 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
- "sr-primitives 2.0.0",
- "sr-std 2.0.0",
- "substrate-client 2.0.0",
-]
-
 [[package]]
 name = "substrate-consensus-rhd"
 version = "2.0.0"
@@ -82,6 +82,7 @@ members = [
 	"srml/generic-asset",
 	"srml/grandpa",
 	"srml/im-online",
+	"srml/authority-discovery",
 	"srml/indices",
 	"srml/membership",
 	"srml/metadata",
@@ -1,5 +1,5 @@
 [package]
-name = "substrate-consensus-common-primitives"
+name = "substrate-authority-discovery-primitives"
 version = "2.0.0"
 authors = ["Parity Technologies <admin@parity.io>"]
 description = "Common consensus primitives"
@@ -7,9 +7,9 @@ edition = "2018"

 [dependencies]
 codec = { package = "parity-scale-codec", default-features = false, version = "1.0.3" }
-client = { package = "substrate-client", path = "../../../client", default-features = false }
-sr-primitives = { path = "../../../sr-primitives", default-features = false }
-rstd = { package = "sr-std", path = "../../../sr-std", default-features = false }
+client = { package = "substrate-client", path = "../../client", default-features = false }
+sr-primitives = { path = "../../sr-primitives", default-features = false }
+rstd = { package = "sr-std", path = "../../sr-std", default-features = false }

 [features]
 default = ["std"]
@@ -0,0 +1,49 @@
+// Copyright 2019 Parity Technologies (UK) Ltd.
+// This file is part of Substrate.
+
+// Substrate is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Substrate is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Runtime Api to help discover authorities.
+
+#![cfg_attr(not(feature = "std"), no_std)]
+
+use client::decl_runtime_apis;
+use codec::Codec;
+use rstd::vec::Vec;
+
+decl_runtime_apis! {
+	/// The authority discovery api.
+	///
+	/// This api is used by the `core/authority-discovery` module to retrieve our
+	/// own authority identifier, to retrieve identifiers of the current authority
+	/// set, as well as sign and verify Kademlia Dht external address payloads
+	/// from and to other authorities.
+	pub trait AuthorityDiscoveryApi<AuthorityId: Codec> {
+		/// Returns own authority identifier iff it is part of the current authority
+		/// set, otherwise this function returns None. The restriction might be
+		/// softened in the future in case a consumer needs to learn own authority
+		/// identifier.
+		fn authority_id() -> Option<AuthorityId>;
+
+		/// Retrieve authority identifiers of the current authority set.
+		fn authorities() -> Vec<AuthorityId>;
+
+		/// Sign the given payload with the private key corresponding to the given authority id.
+		fn sign(payload: Vec<u8>, authority_id: AuthorityId) -> Option<Vec<u8>>;
+
+		/// Verify the given signature for the given payload with the given
+		/// authority identifier.
+		fn verify(payload: Vec<u8>, signature: Vec<u8>, authority_id: AuthorityId) -> bool;
+	}
+}
@@ -1,31 +0,0 @@
-// Copyright 2019 Parity Technologies (UK) Ltd.
-// This file is part of Substrate.
-
-// Substrate is free software: you can redistribute it and/or modify
-// it under the terms of the GNU General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-
-// Substrate is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-// GNU General Public License for more details.
-
-// You should have received a copy of the GNU General Public License
-// along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
-
-//! Common consensus primitives.
-
-#![cfg_attr(not(feature = "std"), no_std)]
-
-use codec::Codec;
-use client::decl_runtime_apis;
-use rstd::vec::Vec;
-
-decl_runtime_apis! {
-	/// Common consensus runtime api.
-	pub trait ConsensusApi<AuthorityId: Codec> {
-		/// Returns the set of authorities of the currently active consensus mechanism.
-		fn authorities() -> Vec<AuthorityId>;
-	}
-}
@@ -89,6 +89,11 @@ impl<H: Hasher, N: ChangesTrieBlockNumber> TestExternalities<H, N> {
 		self.offchain = Some(Box::new(offchain));
 	}

+	/// Set keystore.
+	pub fn set_keystore(&mut self, keystore: BareCryptoStorePtr) {
+		self.keystore = Some(keystore);
+	}
+
 	/// Get mutable reference to changes trie storage.
 	pub fn changes_trie_storage(&mut self) -> &mut ChangesTrieInMemoryStorage<H, N> {
 		&mut self.changes_trie_storage
@@ -25,7 +25,6 @@ timestamp = { package = "srml-timestamp", path = "../../srml/timestamp", default
 sudo = { package = "srml-sudo", path = "../../srml/sudo", default_features = false }
 sr-primitives = { path = "../../core/sr-primitives", default_features = false }
 client = { package = "substrate-client", path = "../../core/client", default_features = false }
-consensus-primitives = { package = "substrate-consensus-common-primitives", path = "../../core/consensus/common/primitives", default-features = false }
 offchain-primitives = { package = "substrate-offchain-primitives", path = "../../core/offchain/primitives", default-features = false }

 [build-dependencies]
@@ -53,7 +52,6 @@ std = [
 	"version/std",
 	"serde",
 	"safe-mix/std",
-	"consensus-primitives/std",
 	"offchain-primitives/std",
 	"substrate-session/std",
 ]
@@ -400,12 +400,6 @@ impl_runtime_apis! {
 		}
 	}

-	impl consensus_primitives::ConsensusApi<Block, babe_primitives::AuthorityId> for Runtime {
-		fn authorities() -> Vec<babe_primitives::AuthorityId> {
-			Babe::authorities().into_iter().map(|(a, _)| a).collect()
-		}
-	}
-
 	impl substrate_session::SessionKeys<Block> for Runtime {
 		fn generate_session_keys(seed: Option<Vec<u8>>) -> Vec<u8> {
 			let seed = seed.as_ref().map(|s| rstd::str::from_utf8(&s).expect("Seed is an utf8 string"));
@@ -46,6 +46,7 @@ system = { package = "srml-system", path = "../../srml/system" }
 balances = { package = "srml-balances", path = "../../srml/balances" }
 support = { package = "srml-support", path = "../../srml/support", default-features = false }
 im_online = { package = "srml-im-online", path = "../../srml/im-online", default-features = false }
+authority-discovery = { package = "srml-authority-discovery", path = "../../srml/authority-discovery", default-features = false }

 [dev-dependencies]
 keystore = { package = "substrate-keystore", path = "../../core/keystore" }
@@ -19,10 +19,9 @@
 use primitives::{Pair, Public, crypto::UncheckedInto};
 pub use node_primitives::{AccountId, Balance};
 use node_runtime::{
-	BabeConfig, BalancesConfig, ContractsConfig, CouncilConfig, DemocracyConfig,
-	ElectionsConfig, GrandpaConfig, ImOnlineConfig, IndicesConfig,
-	SessionConfig, SessionKeys, StakerStatus, StakingConfig, SudoConfig, SystemConfig,
-	TechnicalCommitteeConfig, WASM_BINARY,
+	AuthorityDiscoveryConfig, BabeConfig, BalancesConfig, ContractsConfig, CouncilConfig, DemocracyConfig,
+	ElectionsConfig, GrandpaConfig, ImOnlineConfig, IndicesConfig, SessionConfig, SessionKeys, StakerStatus,
+	StakingConfig, SudoConfig, SystemConfig, TechnicalCommitteeConfig, WASM_BINARY,
 };
 use node_runtime::constants::{time::*, currency::*};
 pub use node_runtime::GenesisConfig;
@@ -171,6 +170,9 @@ fn staging_testnet_config_genesis() -> GenesisConfig {
 		im_online: Some(ImOnlineConfig {
 			keys: vec![],
 		}),
+		authority_discovery: Some(AuthorityDiscoveryConfig{
+			keys: vec![],
+		}),
 		grandpa: Some(GrandpaConfig {
 			authorities: vec![],
 		}),
@@ -302,6 +304,9 @@ pub fn testnet_genesis(
 		im_online: Some(ImOnlineConfig {
 			keys: vec![],
 		}),
+		authority_discovery: Some(AuthorityDiscoveryConfig{
+			keys: vec![],
+		}),
 		grandpa: Some(GrandpaConfig {
 			authorities: vec![],
 		}),
@@ -15,12 +15,12 @@ rstd = { package = "sr-std", path = "../../core/sr-std", default-features = fals
 sr-primitives = { path = "../../core/sr-primitives", default-features = false }
 sr-staking-primitives = { path = "../../core/sr-staking-primitives", default-features = false }
 offchain-primitives = { package = "substrate-offchain-primitives", path = "../../core/offchain/primitives", default-features = false }
+authority-discovery-primitives = { package = "substrate-authority-discovery-primitives", path = "../../core/authority-discovery/primitives", default-features = false }
 version = { package = "sr-version", path = "../../core/sr-version", default-features = false }
 support = { package = "srml-support", path = "../../srml/support", default-features = false }
 authorship = { package = "srml-authorship", path = "../../srml/authorship", default-features = false }
 babe = { package = "srml-babe", path = "../../srml/babe", default-features = false }
 babe-primitives = { package = "substrate-consensus-babe-primitives", path = "../../core/consensus/babe/primitives", default-features = false }
-consensus-primitives = { package = "substrate-consensus-common-primitives", path = "../../core/consensus/common/primitives", default-features = false }
 balances = { package = "srml-balances", path = "../../srml/balances", default-features = false }
 contracts = { package = "srml-contracts", path = "../../srml/contracts", default-features = false }
 collective = { package = "srml-collective", path = "../../srml/collective", default-features = false }
@@ -38,6 +38,7 @@ timestamp = { package = "srml-timestamp", path = "../../srml/timestamp", default
 treasury = { package = "srml-treasury", path = "../../srml/treasury", default-features = false }
 sudo = { package = "srml-sudo", path = "../../srml/sudo", default-features = false }
 im-online = { package = "srml-im-online", path = "../../srml/im-online", default-features = false }
+authority-discovery = { package = "srml-authority-discovery", path = "../../srml/authority-discovery", default-features = false }
 offences = { package = "srml-offences", path = "../../srml/offences", default-features = false }
 node-primitives = { path = "../primitives", default-features = false }
 rustc-hex = { version = "2.0", optional = true }
@@ -54,6 +55,8 @@ no_std = [
 	"contracts/core",
 ]
 std = [
+	"authority-discovery-primitives/std",
+	"authority-discovery/std",
 	"authorship/std",
 	"babe-primitives/std",
 	"babe/std",
@@ -61,7 +64,6 @@ std = [
 	"client/std",
 	"codec/std",
 	"collective/std",
-	"consensus-primitives/std",
 	"contracts/std",
 	"democracy/std",
 	"elections/std",
@@ -80,8 +80,8 @@ pub const VERSION: RuntimeVersion = RuntimeVersion {
 	// and set impl_version to equal spec_version. If only runtime
 	// implementation changes and behavior does not, then leave spec_version as
 	// is and increment impl_version.
-	spec_version: 147,
-	impl_version: 150,
+	spec_version: 148,
+	impl_version: 148,
 	apis: RUNTIME_API_VERSIONS,
 };

@@ -407,6 +407,8 @@ impl offences::Trait for Runtime {
 	type OnOffenceHandler = Staking;
 }

+impl authority_discovery::Trait for Runtime {}
+
 impl grandpa::Trait for Runtime {
 	type Event = Event;
 }
@@ -447,6 +449,7 @@ construct_runtime!(
 		Contracts: contracts,
 		Sudo: sudo,
 		ImOnline: im_online::{Module, Call, Storage, Event, ValidateUnsigned, Config},
+		AuthorityDiscovery: authority_discovery::{Module, Call, Config},
 		Offences: offences::{Module, Call, Storage, Event},
 	}
 );
@@ -576,15 +579,26 @@ impl_runtime_apis! {
 		}
 	}

-	impl node_primitives::AccountNonceApi<Block> for Runtime {
-		fn account_nonce(account: AccountId) -> Index {
-			System::account_nonce(account)
+	impl authority_discovery_primitives::AuthorityDiscoveryApi<Block, im_online::AuthorityId> for Runtime {
+		fn authority_id() -> Option<im_online::AuthorityId> {
+			AuthorityDiscovery::authority_id()
+		}
+		fn authorities() -> Vec<im_online::AuthorityId> {
+			AuthorityDiscovery::authorities()
+		}
+
+		fn sign(payload: Vec<u8>, authority_id: im_online::AuthorityId) -> Option<Vec<u8>> {
+			AuthorityDiscovery::sign(payload, authority_id)
+		}
+
+		fn verify(payload: Vec<u8>, signature: Vec<u8>, public_key: im_online::AuthorityId) -> bool {
+			AuthorityDiscovery::verify(payload, signature, public_key)
 		}
 	}

-	impl consensus_primitives::ConsensusApi<Block, babe_primitives::AuthorityId> for Runtime {
-		fn authorities() -> Vec<babe_primitives::AuthorityId> {
-			Babe::authorities().into_iter().map(|(a, _)| a).collect()
+	impl node_primitives::AccountNonceApi<Block> for Runtime {
+		fn account_nonce(account: AccountId) -> Index {
+			System::account_nonce(account)
 		}
 	}

@@ -89,6 +89,7 @@ pub fn config(support_changes_trie: bool, code: Option<&[u8]>) -> GenesisConfig
 			authorities: vec![],
 		}),
 		im_online: Some(Default::default()),
+		authority_discovery: Some(Default::default()),
 		democracy: Some(Default::default()),
 		collective_Instance1: Some(Default::default()),
 		collective_Instance2: Some(Default::default()),
@@ -0,0 +1,34 @@
+[package]
+name = "srml-authority-discovery"
+version = "0.1.0"
+authors = ["Parity Technologies <admin@parity.io>"]
+edition = "2018"
+
+[dependencies]
+codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
+sr-primitives = { path = "../../core/sr-primitives", default-features = false }
+primitives = { package = "substrate-primitives",  path = "../../core/primitives", default-features = false }
+app-crypto = { package = "substrate-application-crypto", path = "../../core/application-crypto", default-features = false }
+rstd = { package = "sr-std", path = "../../core/sr-std", default-features = false }
+serde = { version = "1.0", optional = true }
+session = { package = "srml-session", path = "../session", default-features = false }
+im-online = { package = "srml-im-online", path = "../im-online", default-features = false }
+srml-support = { path = "../support", default-features = false }
+sr-io = { package = "sr-io", path = "../../core/sr-io", default-features = false }
+system = { package = "srml-system", path = "../system", default-features = false }
+
+[features]
+default = ["std"]
+std = [
+	"codec/std",
+	"sr-primitives/std",
+	"primitives/std",
+	"rstd/std",
+	"serde",
+	"session/std",
+	"im-online/std",
+	"srml-support/std",
+	"sr-io/std",
+	"system/std",
+	"app-crypto/std",
+]
@@ -0,0 +1,349 @@
+// Copyright 2019 Parity Technologies (UK) Ltd.
+// This file is part of Substrate.
+
+// Substrate is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Substrate is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
+
+//! # Authority discovery module.
+//!
+//! This module is used by the `core/authority-discovery` to retrieve the
+//! current set of authorities, learn its own authority id as well as sign and
+//! verify messages to and from other authorities.
+//!
+//! ## Dependencies
+//!
+//! This module depends on the [I’m online module](../srml_im_online/index.html)
+//! using its session key.
+
+// Ensure we're `no_std` when compiling for Wasm.
+#![cfg_attr(not(feature = "std"), no_std)]
+
+use app_crypto::RuntimeAppPublic;
+use codec::{Decode, Encode};
+use rstd::prelude::*;
+use srml_support::{decl_module, decl_storage, StorageValue};
+
+pub trait Trait: system::Trait + session::Trait {}
+
+decl_storage! {
+	trait Store for Module<T: Trait> as AuthorityDiscovery {
+		/// The current set of keys that may issue a heartbeat.
+		Keys get(keys): Vec<im_online::AuthorityId>;
+	}
+	add_extra_genesis {
+		config(keys): Vec<im_online::AuthorityId>;
+		build(|
+			  storage: &mut (sr_primitives::StorageOverlay, sr_primitives::ChildrenStorageOverlay),
+			  config: &GenesisConfig
+			  | {
+				  sr_io::with_storage(
+					  storage,
+					  || Module::<T>::initialize_keys(&config.keys),
+				  );
+			  })
+	}
+}
+
+decl_module! {
+	pub struct Module<T: Trait> for enum Call where origin: T::Origin {
+	}
+}
+
+impl<T: Trait> Module<T> {
+	/// Returns own authority identifier iff it is part of the current authority
+	/// set, otherwise this function returns None. The restriction might be
+	/// softened in the future in case a consumer needs to learn own authority
+	/// identifier.
+	pub fn authority_id() -> Option<im_online::AuthorityId> {
+		let authorities = Keys::get();
+
+		let local_keys = im_online::AuthorityId::all();
+
+		authorities.into_iter().find_map(|authority| {
+			if local_keys.contains(&authority) {
+				Some(authority)
+			} else {
+				None
+			}
+		})
+	}
+
+	/// Retrieve authority identifiers of the current authority set.
+	pub fn authorities() -> Vec<im_online::AuthorityId> {
+		Keys::get()
+	}
+
+	/// Sign the given payload with the private key corresponding to the given authority id.
+	pub fn sign(payload: Vec<u8>, authority_id: im_online::AuthorityId) -> Option<Vec<u8>> {
+		authority_id.sign(&payload).map(|s| s.encode())
+	}
+
+	/// Verify the given signature for the given payload with the given
+	/// authority identifier.
+	pub fn verify(
+		payload: Vec<u8>,
+		signature: Vec<u8>,
+		authority_id: im_online::AuthorityId,
+	) -> bool {
+		im_online::AuthoritySignature::decode(&mut &signature[..])
+			.map(|s| authority_id.verify(&payload, &s))
+			.unwrap_or(false)
+	}
+
+	fn initialize_keys(keys: &[im_online::AuthorityId]) {
+		if !keys.is_empty() {
+			assert!(Keys::get().is_empty(), "Keys are already initialized!");
+			Keys::put_ref(keys);
+		}
+	}
+}
+
+impl<T: Trait> session::OneSessionHandler<T::AccountId> for Module<T> {
+	type Key = im_online::AuthorityId;
+
+	fn on_genesis_session<'a, I: 'a>(validators: I)
+	where
+		I: Iterator<Item = (&'a T::AccountId, im_online::AuthorityId)>,
+	{
+		let keys = validators.map(|x| x.1).collect::<Vec<_>>();
+		Self::initialize_keys(&keys);
+	}
+
+	fn on_new_session<'a, I: 'a>(_changed: bool, _validators: I, next_validators: I)
+	where
+		I: Iterator<Item = (&'a T::AccountId, im_online::AuthorityId)>,
+	{
+		// Remember who the authorities are for the new session.
+		Keys::put(next_validators.map(|x| x.1).collect::<Vec<_>>());
+	}
+
+	fn on_disabled(_i: usize) {
+		// ignore
+	}
+}
+
+#[cfg(test)]
+mod tests {
+	use super::*;
+	use app_crypto::Pair;
+	use primitives::testing::KeyStore;
+	use primitives::{crypto::key_types, sr25519, traits::BareCryptoStore, H256};
+	use sr_io::{with_externalities, TestExternalities};
+	use sr_primitives::testing::{Header, UintAuthorityId};
+	use sr_primitives::traits::{ConvertInto, IdentityLookup, OpaqueKeys};
+	use sr_primitives::Perbill;
+	use srml_support::{impl_outer_origin, parameter_types};
+
+	type AuthorityDiscovery = Module<Test>;
+	type SessionIndex = u32;
+
+	#[derive(Clone, Eq, PartialEq)]
+	pub struct Test;
+	impl Trait for Test {}
+
+	pub struct TestOnSessionEnding;
+	impl session::OnSessionEnding<im_online::AuthorityId> for TestOnSessionEnding {
+		fn on_session_ending(
+			_: SessionIndex,
+			_: SessionIndex,
+		) -> Option<Vec<im_online::AuthorityId>> {
+			None
+		}
+	}
+
+	impl session::Trait for Test {
+		type OnSessionEnding = TestOnSessionEnding;
+		type Keys = UintAuthorityId;
+		type ShouldEndSession = session::PeriodicSessions<Period, Offset>;
+		type SessionHandler = TestSessionHandler;
+		type Event = ();
+		type ValidatorId = im_online::AuthorityId;
+		type ValidatorIdOf = ConvertInto;
+		type SelectInitialValidators = ();
+	}
+
+	pub type BlockNumber = u64;
+
+	parameter_types! {
+		pub const Period: BlockNumber = 1;
+		pub const Offset: BlockNumber = 0;
+		pub const UncleGenerations: u64 = 0;
+		pub const BlockHashCount: u64 = 250;
+		pub const MaximumBlockWeight: u32 = 1024;
+		pub const MaximumBlockLength: u32 = 2 * 1024;
+		pub const AvailableBlockRatio: Perbill = Perbill::one();
+	}
+
+	impl system::Trait for Test {
+		type Origin = Origin;
+		type Index = u64;
+		type BlockNumber = BlockNumber;
+		type Call = ();
+		type Hash = H256;
+		type Hashing = ::sr_primitives::traits::BlakeTwo256;
+		type AccountId = im_online::AuthorityId;
+		type Lookup = IdentityLookup<Self::AccountId>;
+		type Header = Header;
+		type WeightMultiplierUpdate = ();
+		type Event = ();
+		type BlockHashCount = BlockHashCount;
+		type MaximumBlockWeight = MaximumBlockWeight;
+		type AvailableBlockRatio = AvailableBlockRatio;
+		type MaximumBlockLength = MaximumBlockLength;
+		type Version = ();
+	}
+
+	impl_outer_origin! {
+		pub enum Origin for Test {}
+	}
+
+	pub struct TestSessionHandler;
+	impl session::SessionHandler<im_online::AuthorityId> for TestSessionHandler {
+		fn on_new_session<Ks: OpaqueKeys>(
+			_changed: bool,
+			_validators: &[(im_online::AuthorityId, Ks)],
+			_queued_validators: &[(im_online::AuthorityId, Ks)],
+		) {
+		}
+
+		fn on_disabled(_validator_index: usize) {}
+
+		fn on_genesis_session<Ks: OpaqueKeys>(_validators: &[(im_online::AuthorityId, Ks)]) {}
+	}
+
+	#[test]
+	fn authority_id_fn_returns_intersection_of_current_authorities_and_keys_in_key_store() {
+		// Create keystore and generate key.
+		let key_store = KeyStore::new();
+		key_store
+			.write()
+			.sr25519_generate_new(key_types::IM_ONLINE, None)
+			.expect("Generates key.");
+
+		// Retrieve key to later check if we got the right one.
+		let public_key = key_store
+			.read()
+			.sr25519_public_keys(key_types::IM_ONLINE)
+			.pop()
+			.unwrap();
+		let authority_id = im_online::AuthorityId::from(public_key);
+
+		// Build genesis.
+		let mut t = system::GenesisConfig::default()
+			.build_storage::<Test>()
+			.unwrap();
+
+		GenesisConfig {
+			keys: vec![authority_id.clone()],
+		}
+		.assimilate_storage::<Test>(&mut t)
+		.unwrap();
+
+		// Create externalities.
+		let mut externalities = TestExternalities::new(t);
+		externalities.set_keystore(key_store);
+
+		with_externalities(&mut externalities, || {
+			assert_eq!(
+				authority_id,
+				AuthorityDiscovery::authority_id().expect("Retrieving public key.")
+			);
+		});
+	}
+
+	#[test]
+	fn authority_id_fn_does_not_return_key_outside_current_authority_set() {
+		// Create keystore and generate key.
+		let key_store = KeyStore::new();
+		key_store
+			.write()
+			.sr25519_generate_new(key_types::IM_ONLINE, None)
+			.expect("Generates key.");
+
+		// Build genesis.
+		let mut t = system::GenesisConfig::default()
+			.build_storage::<Test>()
+			.unwrap();
+
+		// Generate random authority set.
+		let keys = vec![(); 5]
+			.iter()
+			.map(|_x| sr25519::Pair::generate_with_phrase(None).0.public())
+			.map(im_online::AuthorityId::from)
+			.collect();
+
+		GenesisConfig { keys: keys }
+			.assimilate_storage::<Test>(&mut t)
+			.unwrap();
+
+		// Create externalities.
+		let mut externalities = TestExternalities::new(t);
+		externalities.set_keystore(key_store);
+
+		with_externalities(&mut externalities, || {
+			assert_eq!(None, AuthorityDiscovery::authority_id());
+		});
+	}
+
+	#[test]
+	fn sign_and_verify_workflow() {
+		// Create keystore and generate key.
+		let key_store = KeyStore::new();
+		key_store
+			.write()
+			.sr25519_generate_new(key_types::IM_ONLINE, None)
+			.expect("Generates key.");
+
+		// Retrieve key to later check if we got the right one.
+		let public_key = key_store
+			.read()
+			.sr25519_public_keys(key_types::IM_ONLINE)
+			.pop()
+			.unwrap();
+		let authority_id = im_online::AuthorityId::from(public_key);
+
+		// Build genesis.
+		let mut t = system::GenesisConfig::default()
+			.build_storage::<Test>()
+			.unwrap();
+
+		GenesisConfig {
+			keys: vec![authority_id.clone()],
+		}
+		.assimilate_storage::<Test>(&mut t)
+		.unwrap();
+
+		// Create externalities.
+		let mut externalities = TestExternalities::new(t);
+		externalities.set_keystore(key_store);
+
+		with_externalities(&mut externalities, || {
+			let authority_id = AuthorityDiscovery::authority_id().expect("authority id");
+			let payload = String::from("test payload").into_bytes();
+			let sig =
+				AuthorityDiscovery::sign(payload.clone(), authority_id.clone()).expect("signature");
+
+			assert!(AuthorityDiscovery::verify(
+				payload,
+				sig.clone(),
+				authority_id.clone()
+			));
+
+			assert!(!AuthorityDiscovery::verify(
+				String::from("other payload").into_bytes(),
+				sig,
+				authority_id
+			))
+		});
+	}
+}