Remove rng_seed's additional entropy

It was never used as we derive entropy via the other fields in the 
transcript, and explicitly add fields directly as needed for entropy.

Also drops an unused crate and corrects a bug in FROST's Schnorr 
implementation which used the Group's generator, instead of the Curve's.

Also updates the Monero crate's description.

coins/monero/Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "monero-serai"
 version = "0.1.0"
-description = "Implementation of Monero transaction signing in Rust"
+description = "A modern Monero wallet library"
 license = "MIT"
 authors = ["Luke Parker <lukeparker5132@gmail.com>"]
 edition = "2021"

coins/monero/src/ringct/clsag/multisig.rs

@@ -206,7 +206,7 @@ impl Algorithm<Ed25519> for ClsagMultisig {
     // process even if they have access to commitments (specifically, the ring index being signed
     // for, along with the mask which should not only require knowing the shared keys yet also the
     // input commitment masks)
-    let mut rng = ChaCha12Rng::from_seed(self.transcript.rng_seed(b"decoy_responses", None));
+    let mut rng = ChaCha12Rng::from_seed(self.transcript.rng_seed(b"decoy_responses"));
 
     self.msg = Some(msg.try_into().expect("CLSAG message should be 32-bytes"));
 

coins/monero/src/wallet/send/multisig.rs

@@ -90,7 +90,7 @@ impl SignableTransaction {
     let decoys = Decoys::select(
       // Using a seeded RNG with a specific height, committed to above, should make these decoys
       // committed to. They'll also be committed to later via the TX message as a whole
-      &mut ChaCha12Rng::from_seed(transcript.rng_seed(b"decoys", None)),
+      &mut ChaCha12Rng::from_seed(transcript.rng_seed(b"decoys")),
       rpc,
       height,
       &self.inputs
@@ -216,7 +216,7 @@ impl StateMachine for TransactionMachine {
 
       // Not invalid outputs due to already doing a dummy prep
       let (commitments, output_masks) = self.signable.prepare_outputs(
-        &mut ChaCha12Rng::from_seed(self.transcript.rng_seed(b"tx_keys", None)),
+        &mut ChaCha12Rng::from_seed(self.transcript.rng_seed(b"tx_keys")),
         uniqueness(
           &images.iter().map(|image| Input::ToKey {
             amount: 0,
@@ -230,7 +230,7 @@ impl StateMachine for TransactionMachine {
       self.signable.prepare_transaction(
         &commitments,
         Bulletproofs::new(
-          &mut ChaCha12Rng::from_seed(self.transcript.rng_seed(b"bulletproofs", None)),
+          &mut ChaCha12Rng::from_seed(self.transcript.rng_seed(b"bulletproofs")),
           &commitments
         ).unwrap()
       )
@@ -249,7 +249,7 @@ impl StateMachine for TransactionMachine {
     }
     sorted.sort_by(|x, y| x.2.compress().to_bytes().cmp(&y.2.compress().to_bytes()).reverse());
 
-    let mut rng = ChaCha12Rng::from_seed(self.transcript.rng_seed(b"pseudo_out_masks", None));
+    let mut rng = ChaCha12Rng::from_seed(self.transcript.rng_seed(b"pseudo_out_masks"));
     let mut sum_pseudo_outs = Scalar::zero();
     while sorted.len() != 0 {
       let value = sorted.remove(0);

crypto/frost/Cargo.toml

@@ -14,7 +14,6 @@ rand_core = "0.6"
 ff = "0.11"
 group = "0.11"
 
-blake2 = "0.10"
 transcript = { path = "../transcript" }
 
 multiexp = { path = "../multiexp", features = ["batch"] }

crypto/frost/src/algorithm.rs

@@ -72,7 +72,7 @@ impl Transcript for IetfTranscript {
     self.0.clone()
   }
 
-  fn rng_seed(&mut self, _: &'static [u8], _: Option<[u8; 32]>) -> [u8; 32] {
+  fn rng_seed(&mut self, _: &'static [u8]) -> [u8; 32] {
     unimplemented!()
   }
 }

crypto/frost/src/schnorr.rs

@@ -1,7 +1,6 @@
 use rand_core::{RngCore, CryptoRng};
 
 use ff::Field;
-use group::Group;
 
 use multiexp::BatchVerifier;
 
@@ -46,7 +45,7 @@ pub(crate) fn batch_verify<C: Curve, R: RngCore + CryptoRng>(
   rng: &mut R,
   triplets: &[(u16, C::G, C::F, SchnorrSignature<C>)]
 ) -> Result<(), u16> {
-  let mut values = [(C::F::one(), C::G::generator()); 3];
+  let mut values = [(C::F::one(), C::generator()); 3];
   let mut batch = BatchVerifier::new(triplets.len(), C::little_endian());
   for triple in triplets {
     // s = r + ca

crypto/transcript/src/lib.rs

@@ -11,7 +11,7 @@ pub trait Transcript {
   fn domain_separate(&mut self, label: &[u8]);
   fn append_message(&mut self, label: &'static [u8], message: &[u8]);
   fn challenge(&mut self, label: &'static [u8]) -> Vec<u8>;
-  fn rng_seed(&mut self, label: &'static [u8], additional_entropy: Option<[u8; 32]>) -> [u8; 32];
+  fn rng_seed(&mut self, label: &'static [u8]) -> [u8; 32];
 }
 
 #[derive(Clone, Debug)]
@@ -49,11 +49,7 @@ impl<D: Digest> Transcript for DigestTranscript<D> {
     D::new().chain_update(&self.0).finalize().to_vec()
   }
 
-  fn rng_seed(&mut self, label: &'static [u8], additional_entropy: Option<[u8; 32]>) -> [u8; 32] {
+  fn rng_seed(&mut self, label: &'static [u8]) -> [u8; 32] {
-    if additional_entropy.is_some() {
-      self.append_message(b"additional_entropy", &additional_entropy.unwrap());
-    }
-
     let mut seed = [0; 32];
     seed.copy_from_slice(&self.challenge(label)[0 .. 32]);
     seed

crypto/transcript/src/merlin.rs

@@ -30,11 +30,7 @@ impl Transcript for MerlinTranscript {
     challenge
   }
 
-  fn rng_seed(&mut self, label: &'static [u8], additional_entropy: Option<[u8; 32]>) -> [u8; 32] {
+  fn rng_seed(&mut self, label: &'static [u8]) -> [u8; 32] {
-    if additional_entropy.is_some() {
-      transcript.append_message(b"additional_entropy", &additional_entropy.unwrap());
-    }
-
     let mut seed = [0; 32];
     transcript.challenge_bytes(label, &mut seed);
     seed