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/core/src/crypto.rs

@@ -28,11 +28,8 @@ use rand::{rngs::OsRng, RngCore};
 #[cfg(feature = "std")]
 use regex::Regex;
 use scale_info::TypeInfo;
-/// Trait for accessing reference to `SecretString`.
-pub use secrecy::ExposeSecret;
-/// A store for sensitive data.
 #[cfg(feature = "std")]
-pub use secrecy::SecretString;
+pub use secrecy::{ExposeSecret, SecretString};
 use sp_runtime_interface::pass_by::PassByInner;
 #[doc(hidden)]
 pub use sp_std::ops::Deref;
@@ -1102,6 +1099,27 @@ impl<'a> TryFrom<&'a str> for KeyTypeId {
 	}
 }
 
+/// Trait grouping types shared by a VRF signer and verifiers.
+pub trait VrfCrypto {
+	/// Associated signature type.
+	type VrfSignature;
+
+	/// Vrf input data. Generally some form of transcript.
+	type VrfInput;
+}
+
+/// VRF Signer.
+pub trait VrfSigner: VrfCrypto {
+	/// Sign input data.
+	fn vrf_sign(&self, data: &Self::VrfInput) -> Self::VrfSignature;
+}
+
+/// VRF Verifier.
+pub trait VrfVerifier: VrfCrypto {
+	/// Verify input data signature.
+	fn vrf_verify(&self, data: &Self::VrfInput, signature: &Self::VrfSignature) -> bool;
+}
+
 /// An identifier for a specific cryptographic algorithm used by a key pair
 #[derive(Debug, Copy, Clone, Default, PartialEq, Eq, PartialOrd, Ord, Hash, Encode, Decode)]
 #[cfg_attr(feature = "std", derive(serde::Serialize, serde::Deserialize))]