Refinements to VRF types (#14036)

* Allow extra signing data

* Fix tests after renaming

* Rename VrfSecret/VrfVerifier to VrfSecret/VrfPublic

* Further encrapsulation of 'transcript' type to the sr25519 implementation

* Keystore sr25519 pre-output

* Leave additional custom input field hidden in the associated VrfInput type

* Fix test

* More ergonomic output_bytes

* Trigger pipeline

* Define a separated type for vrf signature data

* Fix docs

* Fix doc

* Remove annotation

* Directly use dleq_proove and dleq_verify in sr25519

* Trigger CI

* Remove cruft before merge

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

@@ -32,7 +32,9 @@ use sp_std::vec::Vec;
 
 use crate::digests::{NextConfigDescriptor, NextEpochDescriptor};
 
-pub use sp_core::sr25519::vrf::{VrfOutput, VrfProof, VrfSignature, VrfTranscript};
+pub use sp_core::sr25519::vrf::{
+	VrfInput, VrfOutput, VrfProof, VrfSignData, VrfSignature, VrfTranscript,
+};
 
 /// Key type for BABE module.
 pub const KEY_TYPE: sp_core::crypto::KeyTypeId = sp_application_crypto::key_types::BABE;
@@ -94,9 +96,9 @@ pub type BabeAuthorityWeight = u64;
 /// of 0 (regardless of whether they are plain or vrf secondary blocks).
 pub type BabeBlockWeight = u32;
 
-/// Make a VRF transcript data container
-pub fn make_transcript(randomness: &Randomness, slot: Slot, epoch: u64) -> VrfTranscript {
-	VrfTranscript::new(
+/// Make VRF input suitable for BABE's randomness generation.
+pub fn make_vrf_transcript(randomness: &Randomness, slot: Slot, epoch: u64) -> VrfInput {
+	VrfInput::new(
 		&BABE_ENGINE_ID,
 		&[
 			(b"slot number", &slot.to_le_bytes()),
@@ -106,6 +108,11 @@ pub fn make_transcript(randomness: &Randomness, slot: Slot, epoch: u64) -> VrfTr
 	)
 }
 
+/// Make VRF signing data suitable for BABE's protocol.
+pub fn make_vrf_sign_data(randomness: &Randomness, slot: Slot, epoch: u64) -> VrfSignData {
+	make_vrf_transcript(randomness, slot, epoch).into()
+}
+
 /// An consensus log item for BABE.
 #[derive(Decode, Encode, Clone, PartialEq, Eq)]
 pub enum ConsensusLog {