From ffdd739f859b89ea412ef4ad844f332baea8410b Mon Sep 17 00:00:00 2001
From: therealyingtong <yingtong@z.cash>
Date: Fri, 22 Jan 2021 12:31:27 +0800
Subject: [PATCH] Only write k in Params; calculate n when reading

Co-authored-by: Jack Grigg <jack@electriccoin.co>
Co-authored-by: Daira Hopwood <daira@jacaranda.org>
---
 src/plonk/keygen.rs             | 6 +++---
 src/plonk/permutation/keygen.rs | 4 ++--
 src/poly/commitment.rs          | 5 +----
 src/poly/commitment/prover.rs   | 4 ++--
 4 files changed, 8 insertions(+), 11 deletions(-)

diff --git a/src/plonk/keygen.rs b/src/plonk/keygen.rs
index 8128934..8c99b7a 100644
--- a/src/plonk/keygen.rs
+++ b/src/plonk/keygen.rs
@@ -56,7 +56,7 @@ where
 }
 
 /// Assembly to be used in circuit synthesis.
-#[derive(Clone, Debug)]
+#[derive(Debug)]
 pub struct Assembly<F: Field> {
     fixed: Vec<Polynomial<F, LagrangeCoeff>>,
     permutations: Vec<permutation::keygen::Assembly>,
@@ -127,7 +127,7 @@ where
         _marker: std::marker::PhantomData,
     };
 
-    // Synthesize the circuit to obtain SRS
+    // Synthesize the circuit to obtain URS
     circuit.synthesize(&mut assembly, config)?;
 
     let permutation_helper = permutation::keygen::Assembly::build_helper(params, &cs, &domain);
@@ -177,7 +177,7 @@ where
         _marker: std::marker::PhantomData,
     };
 
-    // Synthesize the circuit to obtain SRS
+    // Synthesize the circuit to obtain URS
     circuit.synthesize(&mut assembly, config)?;
 
     let fixed_polys: Vec<_> = assembly
diff --git a/src/plonk/permutation/keygen.rs b/src/plonk/permutation/keygen.rs
index d527725..072f6c5 100644
--- a/src/plonk/permutation/keygen.rs
+++ b/src/plonk/permutation/keygen.rs
@@ -14,7 +14,7 @@ pub(crate) struct AssemblyHelper<C: CurveAffine> {
     deltaomega: Vec<Vec<C::Scalar>>,
 }
 
-#[derive(Clone, Debug)]
+#[derive(Debug)]
 pub(crate) struct Assembly {
     pub(crate) mapping: Vec<Vec<(usize, usize)>>,
     aux: Vec<Vec<(usize, usize)>>,
@@ -139,7 +139,7 @@ impl Assembly {
         helper: &AssemblyHelper<C>,
         p: &Argument,
     ) -> VerifyingKey<C> {
-        // Pre-compute commitments for the SRS.
+        // Pre-compute commitments for the URS.
         let mut commitments = vec![];
         for i in 0..p.columns.len() {
             // Computes the permutation polynomial based on the permutation
diff --git a/src/poly/commitment.rs b/src/poly/commitment.rs
index 55517d3..f4098a8 100644
--- a/src/poly/commitment.rs
+++ b/src/poly/commitment.rs
@@ -194,7 +194,6 @@ impl<C: CurveAffine> Params<C> {
     /// Writes params to a buffer.
     pub fn write<W: io::Write>(&self, writer: &mut W) -> io::Result<()> {
         writer.write_all(&self.k.to_le_bytes())?;
-        writer.write_all(&self.n.to_le_bytes())?;
         for g_element in &self.g {
             writer.write_all(&g_element.to_bytes())?;
         }
@@ -213,9 +212,7 @@ impl<C: CurveAffine> Params<C> {
         reader.read_exact(&mut k[..])?;
         let k = u32::from_le_bytes(k);
 
-        let mut n = [0u8; 8];
-        reader.read_exact(&mut n[..])?;
-        let n = u64::from_le_bytes(n);
+        let n: u64 = 1 << k;
 
         let g: Vec<_> = (0..n).map(|_| C::read(reader)).collect::<Result<_, _>>()?;
         let g_lagrange: Vec<_> = (0..n).map(|_| C::read(reader)).collect::<Result<_, _>>()?;
diff --git a/src/poly/commitment/prover.rs b/src/poly/commitment/prover.rs
index 3f51865..4710821 100644
--- a/src/poly/commitment/prover.rs
+++ b/src/poly/commitment/prover.rs
@@ -20,7 +20,7 @@ use std::io;
 /// **Important:** This function assumes that the provided `transcript` has
 /// already seen the common inputs: the polynomial commitment P, the claimed
 /// opening v, and the point x. It's probably also nice for the transcript
-/// to have seen the elliptic curve description and the SRS, if you want to
+/// to have seen the elliptic curve description and the URS, if you want to
 /// be rigorous.
 pub fn create_proof<C: CurveAffine, T: TranscriptWrite<C>>(
     params: &Params<C>,
@@ -82,7 +82,7 @@ pub fn create_proof<C: CurveAffine, T: TranscriptWrite<C>>(
         }
     }
 
-    // Initialize the vector `G` from the SRS. We'll be progressively collapsing
+    // Initialize the vector `G` from the URS. We'll be progressively collapsing
     // this vector into smaller and smaller vectors until it is of length 1.
     let mut g = params.g.clone();