VRF refactory (#13889)

* First iteration to encapsulate schnorrkel and merlin usage

* Remove schnorkel direct dependency from BABE pallet

* Remove schnorrkel direct dependency from BABE client

* Trivial renaming for VrfTranscript data and value

* Better errors

* Expose a function to get a schnorrkel friendly transcript

* Keep the vrf signature stuff together (preventing some clones around)

* Fix tests

* Remove vrf agnostic transcript and define it as an associated type for VrfSigner and VrfVerifier

* Fix babe pallet mock

* Inner types are required to be public for polkadot

* Update client/consensus/babe/src/verification.rs

Co-authored-by: Koute <koute@users.noreply.github.com>

* Nit

* Remove Deref implementations

* make_bytes as a method

* Trigger CI

---------

Co-authored-by: Koute <koute@users.noreply.github.com>

substrate/primitives/consensus/babe/src/digests.rs

@@ -19,14 +19,15 @@
 
 use super::{
 	AllowedSlots, AuthorityId, AuthorityIndex, AuthoritySignature, BabeAuthorityWeight,
-	BabeEpochConfiguration, Slot, BABE_ENGINE_ID,
+	BabeEpochConfiguration, Randomness, Slot, BABE_ENGINE_ID,
 };
-use codec::{Decode, Encode, MaxEncodedLen};
-use scale_info::TypeInfo;
+
+use sp_core::sr25519::vrf::VrfSignature;
 use sp_runtime::{DigestItem, RuntimeDebug};
 use sp_std::vec::Vec;
 
-use sp_consensus_vrf::schnorrkel::{Randomness, VRFOutput, VRFProof};
+use codec::{Decode, Encode, MaxEncodedLen};
+use scale_info::TypeInfo;
 
 /// Raw BABE primary slot assignment pre-digest.
 #[derive(Clone, RuntimeDebug, Encode, Decode, MaxEncodedLen, TypeInfo)]
@@ -35,10 +36,8 @@ pub struct PrimaryPreDigest {
 	pub authority_index: super::AuthorityIndex,
 	/// Slot
 	pub slot: Slot,
-	/// VRF output
-	pub vrf_output: VRFOutput,
-	/// VRF proof
-	pub vrf_proof: VRFProof,
+	/// VRF signature
+	pub vrf_signature: VrfSignature,
 }
 
 /// BABE secondary slot assignment pre-digest.
@@ -62,10 +61,8 @@ pub struct SecondaryVRFPreDigest {
 	pub authority_index: super::AuthorityIndex,
 	/// Slot
 	pub slot: Slot,
-	/// VRF output
-	pub vrf_output: VRFOutput,
-	/// VRF proof
-	pub vrf_proof: VRFProof,
+	/// VRF signature
+	pub vrf_signature: VrfSignature,
 }
 
 /// A BABE pre-runtime digest. This contains all data required to validate a
@@ -118,11 +115,10 @@ impl PreDigest {
 	}
 
 	/// Returns the VRF output and proof, if they exist.
-	pub fn vrf(&self) -> Option<(&VRFOutput, &VRFProof)> {
+	pub fn vrf_signature(&self) -> Option<&VrfSignature> {
 		match self {
-			PreDigest::Primary(primary) => Some((&primary.vrf_output, &primary.vrf_proof)),
-			PreDigest::SecondaryVRF(secondary) =>
-				Some((&secondary.vrf_output, &secondary.vrf_proof)),
+			PreDigest::Primary(primary) => Some(&primary.vrf_signature),
+			PreDigest::SecondaryVRF(secondary) => Some(&secondary.vrf_signature),
 			PreDigest::SecondaryPlain(_) => None,
 		}
 	}

substrate/primitives/consensus/babe/src/lib.rs

@@ -23,22 +23,17 @@
 pub mod digests;
 pub mod inherents;
 
-pub use merlin::Transcript;
-pub use sp_consensus_vrf::schnorrkel::{
-	Randomness, RANDOMNESS_LENGTH, VRF_OUTPUT_LENGTH, VRF_PROOF_LENGTH,
-};
-
 use codec::{Decode, Encode, MaxEncodedLen};
 use scale_info::TypeInfo;
 #[cfg(feature = "std")]
 use serde::{Deserialize, Serialize};
-#[cfg(feature = "std")]
-use sp_keystore::vrf::{VRFTranscriptData, VRFTranscriptValue};
 use sp_runtime::{traits::Header, ConsensusEngineId, RuntimeDebug};
 use sp_std::vec::Vec;
 
 use crate::digests::{NextConfigDescriptor, NextEpochDescriptor};
 
+pub use sp_core::sr25519::vrf::{VrfOutput, VrfProof, VrfSignature, VrfTranscript};
+
 /// Key type for BABE module.
 pub const KEY_TYPE: sp_core::crypto::KeyTypeId = sp_application_crypto::key_types::BABE;
 
@@ -47,11 +42,14 @@ mod app {
 	app_crypto!(sr25519, BABE);
 }
 
-/// The prefix used by BABE for its VRF keys.
-pub const BABE_VRF_PREFIX: &[u8] = b"substrate-babe-vrf";
+/// VRF context used for per-slot randomness generation.
+pub const RANDOMNESS_VRF_CONTEXT: &[u8] = b"BabeVRFInOutContext";
 
-/// BABE VRFInOut context.
-pub static BABE_VRF_INOUT_CONTEXT: &[u8] = b"BabeVRFInOutContext";
+/// VRF output length for per-slot randomness.
+pub const RANDOMNESS_LENGTH: usize = 32;
+
+/// Randomness type required by BABE operations.
+pub type Randomness = [u8; RANDOMNESS_LENGTH];
 
 /// A Babe authority keypair. Necessarily equivalent to the schnorrkel public key used in
 /// the main Babe module. If that ever changes, then this must, too.
@@ -96,26 +94,16 @@ pub type BabeAuthorityWeight = u64;
 /// of 0 (regardless of whether they are plain or vrf secondary blocks).
 pub type BabeBlockWeight = u32;
 
-/// Make a VRF transcript from given randomness, slot number and epoch.
-pub fn make_transcript(randomness: &Randomness, slot: Slot, epoch: u64) -> Transcript {
-	let mut transcript = Transcript::new(&BABE_ENGINE_ID);
-	transcript.append_u64(b"slot number", *slot);
-	transcript.append_u64(b"current epoch", epoch);
-	transcript.append_message(b"chain randomness", &randomness[..]);
-	transcript
-}
-
 /// Make a VRF transcript data container
-#[cfg(feature = "std")]
-pub fn make_transcript_data(randomness: &Randomness, slot: Slot, epoch: u64) -> VRFTranscriptData {
-	VRFTranscriptData {
-		label: &BABE_ENGINE_ID,
-		items: vec![
-			("slot number", VRFTranscriptValue::U64(*slot)),
-			("current epoch", VRFTranscriptValue::U64(epoch)),
-			("chain randomness", VRFTranscriptValue::Bytes(randomness.to_vec())),
+pub fn make_transcript(randomness: &Randomness, slot: Slot, epoch: u64) -> VrfTranscript {
+	VrfTranscript::new(
+		&BABE_ENGINE_ID,
+		&[
+			(b"slot number", &slot.to_le_bytes()),
+			(b"current epoch", &epoch.to_le_bytes()),
+			(b"chain randomness", randomness),
 		],
-	}
+	)
 }
 
 /// An consensus log item for BABE.
@@ -355,7 +343,7 @@ pub struct Epoch {
 	/// The authorities and their weights.
 	pub authorities: Vec<(AuthorityId, BabeAuthorityWeight)>,
 	/// Randomness for this epoch.
-	pub randomness: [u8; VRF_OUTPUT_LENGTH],
+	pub randomness: Randomness,
 	/// Configuration of the epoch.
 	pub config: BabeEpochConfiguration,
 }