Rename the coins folder to networks (#583)

* Rename the coins folder to networks

Ethereum isn't a coin. It's a network.

Resolves #357.

* More renames of coins -> networks in orchestration

* Correct paths in tests/

* cargo fmt

networks/monero/ringct/borromean/src/lib.rs

@@ -0,0 +1,112 @@
+#![cfg_attr(docsrs, feature(doc_auto_cfg))]
+#![doc = include_str!("../README.md")]
+#![deny(missing_docs)]
+#![cfg_attr(not(feature = "std"), no_std)]
+#![allow(non_snake_case)]
+
+use core::fmt::Debug;
+use std_shims::io::{self, Read, Write};
+
+use zeroize::Zeroize;
+
+use curve25519_dalek::{traits::Identity, Scalar, EdwardsPoint};
+
+use monero_io::*;
+use monero_generators::H_pow_2;
+use monero_primitives::{keccak256_to_scalar, UnreducedScalar};
+
+// 64 Borromean ring signatures, as needed for a 64-bit range proof.
+//
+// s0 and s1 are stored as `UnreducedScalar`s due to Monero not requiring they were reduced.
+// `UnreducedScalar` preserves their original byte encoding and implements a custom reduction
+// algorithm which was in use.
+#[derive(Clone, PartialEq, Eq, Debug, Zeroize)]
+struct BorromeanSignatures {
+  s0: [UnreducedScalar; 64],
+  s1: [UnreducedScalar; 64],
+  ee: Scalar,
+}
+
+impl BorromeanSignatures {
+  // Read a set of BorromeanSignatures.
+  fn read<R: Read>(r: &mut R) -> io::Result<BorromeanSignatures> {
+    Ok(BorromeanSignatures {
+      s0: read_array(UnreducedScalar::read, r)?,
+      s1: read_array(UnreducedScalar::read, r)?,
+      ee: read_scalar(r)?,
+    })
+  }
+
+  // Write the set of BorromeanSignatures.
+  fn write<W: Write>(&self, w: &mut W) -> io::Result<()> {
+    for s0 in &self.s0 {
+      s0.write(w)?;
+    }
+    for s1 in &self.s1 {
+      s1.write(w)?;
+    }
+    write_scalar(&self.ee, w)
+  }
+
+  fn verify(&self, keys_a: &[EdwardsPoint], keys_b: &[EdwardsPoint]) -> bool {
+    let mut transcript = [0; 2048];
+
+    for i in 0 .. 64 {
+      #[allow(non_snake_case)]
+      let LL = EdwardsPoint::vartime_double_scalar_mul_basepoint(
+        &self.ee,
+        &keys_a[i],
+        &self.s0[i].recover_monero_slide_scalar(),
+      );
+      #[allow(non_snake_case)]
+      let LV = EdwardsPoint::vartime_double_scalar_mul_basepoint(
+        &keccak256_to_scalar(LL.compress().as_bytes()),
+        &keys_b[i],
+        &self.s1[i].recover_monero_slide_scalar(),
+      );
+      transcript[(i * 32) .. ((i + 1) * 32)].copy_from_slice(LV.compress().as_bytes());
+    }
+
+    keccak256_to_scalar(transcript) == self.ee
+  }
+}
+
+/// A range proof premised on Borromean ring signatures.
+#[derive(Clone, PartialEq, Eq, Debug, Zeroize)]
+pub struct BorromeanRange {
+  sigs: BorromeanSignatures,
+  bit_commitments: [EdwardsPoint; 64],
+}
+
+impl BorromeanRange {
+  /// Read a BorromeanRange proof.
+  pub fn read<R: Read>(r: &mut R) -> io::Result<BorromeanRange> {
+    Ok(BorromeanRange {
+      sigs: BorromeanSignatures::read(r)?,
+      bit_commitments: read_array(read_point, r)?,
+    })
+  }
+
+  /// Write the BorromeanRange proof.
+  pub fn write<W: Write>(&self, w: &mut W) -> io::Result<()> {
+    self.sigs.write(w)?;
+    write_raw_vec(write_point, &self.bit_commitments, w)
+  }
+
+  /// Verify the commitment contains a 64-bit value.
+  #[must_use]
+  pub fn verify(&self, commitment: &EdwardsPoint) -> bool {
+    if &self.bit_commitments.iter().sum::<EdwardsPoint>() != commitment {
+      return false;
+    }
+
+    #[allow(non_snake_case)]
+    let H_pow_2 = H_pow_2();
+    let mut commitments_sub_one = [EdwardsPoint::identity(); 64];
+    for i in 0 .. 64 {
+      commitments_sub_one[i] = self.bit_commitments[i] - H_pow_2[i];
+    }
+
+    self.sigs.verify(&self.bit_commitments, &commitments_sub_one)
+  }
+}