update MLSAG, ss2_elements will always be 2

coins/monero/generators/src/lib.rs

@@ -11,6 +11,7 @@ use sha3::{Digest, Keccak256};
 use curve25519_dalek::edwards::{EdwardsPoint as DalekPoint, CompressedEdwardsY};
 use curve25519_dalek::scalar::Scalar;
 
+use std_shims::vec::Vec;
 use group::{Group, GroupEncoding};
 use dalek_ff_group::EdwardsPoint;
 

coins/monero/src/ringct/borromean.rs

@@ -29,8 +29,8 @@ pub struct BorroSig {
 impl BorroSig {
   pub fn read<R: Read>(r: &mut R) -> io::Result<BorroSig> {
     Ok(BorroSig {
-      s0: read_64_array(read_bytes, r)?,
-      s1: read_64_array(read_bytes, r)?,
+      s0: read_array(read_bytes, r)?,
+      s1: read_array(read_bytes, r)?,
       ee: read_bytes(r)?,
     })
   }
@@ -53,7 +53,7 @@ pub struct RangeSig {
 
 impl RangeSig {
   pub fn read<R: Read>(r: &mut R) -> io::Result<RangeSig> {
-    Ok(RangeSig { asig: BorroSig::read(r)?, Ci: read_64_array(read_point, r)? })
+    Ok(RangeSig { asig: BorroSig::read(r)?, Ci: read_array(read_point, r)? })
   }
   pub fn write<W: Write>(&self, w: &mut W) -> io::Result<()> {
     self.asig.write(w)?;

coins/monero/src/ringct/mlsag/mod.rs

@@ -9,14 +9,14 @@ use curve25519_dalek::edwards::EdwardsPoint;
 use crate::{hash_to_scalar, serialize::*};
 use crate::ringct::hash_to_point;
 
-/// MLSAG signature, as used in Monero.
+/// MgSig part of MLSAG, as used in Monero.
 #[derive(Clone, PartialEq, Eq, Debug)]
-pub struct Mlsag {
-  pub ss: Vec<Vec<Scalar>>,
+pub struct MgSig {
+  pub ss: Vec<[Scalar; 2]>,
   pub cc: Scalar,
 }
 
-impl Mlsag {
+impl MgSig {
   pub fn write<W: Write>(&self, w: &mut W) -> io::Result<()> {
     for ss in self.ss.iter() {
       write_raw_vec(write_scalar, ss, w)?;
@@ -24,11 +24,9 @@ impl Mlsag {
     write_scalar(&self.cc, w)
   }
 
-  pub fn read<R: Read>(mixins: usize, ss2_elements: usize, r: &mut R) -> io::Result<Mlsag> {
-    Ok(Mlsag {
-      ss: (0 .. mixins)
-        .map(|_| read_raw_vec(read_scalar, ss2_elements, r))
-        .collect::<Result<_, _>>()?,
+  pub fn read<R: Read>(mixins: usize, r: &mut R) -> io::Result<MgSig> {
+    Ok(MgSig {
+      ss: (0 .. mixins).map(|_| read_array(read_scalar, r)).collect::<Result<_, _>>()?,
       cc: read_scalar(r)?,
     })
   }

coins/monero/src/ringct/mod.rs

@@ -20,7 +20,7 @@ pub mod bulletproofs;
 use crate::{
   Protocol,
   serialize::*,
-  ringct::{clsag::Clsag, mlsag::Mlsag, bulletproofs::Bulletproofs, borromean::RangeSig},
+  ringct::{clsag::Clsag, mlsag::MgSig, bulletproofs::Bulletproofs, borromean::RangeSig},
 };
 
 /// Generate a key image for a given key. Defined as `x * hash_to_point(xG)`.
@@ -197,17 +197,10 @@ impl RctPrunable {
   ) -> io::Result<RctPrunable> {
     Ok(match rct_type {
       0 => RctPrunable::Null,
-      1 => RctPrunable::Borromean {
+      1 | 2 => RctPrunable::Borromean {
         range_sigs: read_raw_vec(RangeSig::read, outputs, r)?,
-        mlsags: vec![Mlsag::read(decoys[0], 1 + decoys.len(), r)?],
-        simple: false,
-      },
-      2 => RctPrunable::Borromean {
-        range_sigs: read_raw_vec(RangeSig::read, outputs, r)?,
-        mlsags: (0 .. decoys.len())
-          .map(|o| Mlsag::read(decoys[o], 2, r))
-          .collect::<Result<_, _>>()?,
-        simple: true,
+        mlsags: decoys.iter().map(|d| MgSig::read(*d, r)).collect::<Result<_, _>>()?,
+        simple: rct_type == 2,
       },
       3 | 4 => RctPrunable::BulletProof {
         bulletproofs: read_raw_vec(
@@ -219,7 +212,7 @@ impl RctPrunable {
           },
           r,
         )?,
-        mlsags: decoys.iter().map(|d| Mlsag::read(*d, 2, r)).collect::<Result<_, _>>()?,
+        mlsags: decoys.iter().map(|d| MgSig::read(*d, r)).collect::<Result<_, _>>()?,
         pseudo_outs: read_raw_vec(read_point, decoys.len(), r)?,
         v2: rct_type == 4,
       },

coins/monero/src/serialize.rs

@@ -145,9 +145,9 @@ pub(crate) fn read_vec<R: Read, T, F: Fn(&mut R) -> io::Result<T>>(
   read_raw_vec(f, read_varint(r)?.try_into().unwrap(), r)
 }
 
-pub(crate) fn read_64_array<R: Read, T: Debug, F: Fn(&mut R) -> io::Result<T>>(
+pub(crate) fn read_array<const N: usize, R: Read, T: Debug, F: Fn(&mut R) -> io::Result<T>>(
   f: F,
   r: &mut R,
-) -> io::Result<[T; 64]> {
-  (0 .. 64).map(|_| f(r)).collect::<io::Result<Vec<T>>>().map(|vec| vec.try_into().unwrap())
+) -> io::Result<[T; N]> {
+  (0 .. N).map(|_| f(r)).collect::<io::Result<Vec<T>>>().map(|vec| vec.try_into().unwrap())
 }