Use pre-computed generator tables

ergoplatform · Dec 1, 2024 · 98654ba · 98654ba
1 parent af69856
commit 98654ba
Show file tree

Hide file tree

Showing 3 changed files with 12 additions and 7 deletions.
diff --git a/ergo-chain-types/src/ec_point.rs b/ergo-chain-types/src/ec_point.rs
@@ -1,6 +1,7 @@
 //! Elliptic curve point.
 
 use derive_more::{From, Into};
+use elliptic_curve::ops::MulByGenerator;
 use k256::elliptic_curve::group::prime::PrimeCurveAffine;
 use k256::elliptic_curve::sec1::ToEncodedPoint;
 use k256::{ProjectivePoint, PublicKey, Scalar};
@@ -116,6 +117,11 @@ pub fn exponentiate(base: &EcPoint, exponent: &Scalar) -> EcPoint {
     }
 }
 
+/// Raise the generator g to the exponent. This is faster than exponentiate(&generator(), exponent)
+pub fn exponentiate_gen(exponent: &Scalar) -> EcPoint {
+    ProjectivePoint::mul_by_generator(exponent).into()
+}
+
 impl ScorexSerializable for EcPoint {
     fn scorex_serialize<W: WriteSigmaVlqExt>(&self, w: &mut W) -> ScorexSerializeResult {
         let caff = self.0.to_affine();

diff --git a/ergotree-interpreter/src/sigma_protocol/dlog_protocol.rs b/ergotree-interpreter/src/sigma_protocol/dlog_protocol.rs
@@ -44,6 +44,7 @@ pub mod interactive_prover {
     use crate::sigma_protocol::crypto_utils;
     use crate::sigma_protocol::wscalar::Wscalar;
     use crate::sigma_protocol::{private_input::DlogProverInput, Challenge};
+    use ergo_chain_types::ec_point::exponentiate_gen;
     use ergo_chain_types::{
         ec_point::{exponentiate, generator, inverse},
         EcPoint,
@@ -67,7 +68,7 @@ pub mod interactive_prover {
         let e: Scalar = challenge.clone().into();
         let minus_e = e.negate();
         let h_to_e = exponentiate(&public_input.h, &minus_e);
-        let g_to_z = exponentiate(&generator(), &z);
+        let g_to_z = exponentiate_gen(&z);
         let a = g_to_z * &h_to_e;
         (
             FirstDlogProverMessage { a: a.into() },
@@ -80,8 +81,7 @@ pub mod interactive_prover {
     /// that leaf to compute the necessary randomness "r" and the commitment "a"
     pub fn first_message() -> (Wscalar, FirstDlogProverMessage) {
         let r = dlog_group::random_scalar_in_group_range(crypto_utils::secure_rng());
-        let g = generator();
-        let a = exponentiate(&g, &r);
+        let a = exponentiate_gen(&r);
         (r.into(), FirstDlogProverMessage { a: a.into() })
     }
 
@@ -115,7 +115,7 @@ pub mod interactive_prover {
         let g = generator();
         let h = *proposition.h.clone();
         let e: Scalar = challenge.clone().into();
-        let g_z = exponentiate(&g, second_message.z.as_scalar_ref());
+        let g_z = exponentiate_gen(second_message.z.as_scalar_ref());
         let h_e = exponentiate(&h, &e);
         g_z * &inverse(&h_e)
     }

diff --git a/ergotree-interpreter/src/sigma_protocol/private_input.rs b/ergotree-interpreter/src/sigma_protocol/private_input.rs
@@ -2,7 +2,7 @@
 use std::convert::TryInto;
 use std::fmt::Formatter;
 
-use elliptic_curve::ops::MulByGenerator;
+use ergo_chain_types::ec_point::exponentiate_gen;
 use ergo_chain_types::EcPoint;
 use ergotree_ir::serialization::SigmaSerializable;
 use ergotree_ir::sigma_protocol::dlog_group;
@@ -14,7 +14,6 @@ use ergotree_ir::sigma_protocol::sigma_boolean::SigmaBoolean;
 extern crate derive_more;
 use derive_more::From;
 use k256::elliptic_curve::PrimeField;
-use k256::ProjectivePoint;
 use num_bigint::BigUint;
 use num_traits::ToPrimitive;
 
@@ -52,7 +51,7 @@ impl DlogProverInput {
     /// Create new DlogProverInput
     pub fn new(w: Wscalar) -> DlogProverInput {
         Self {
-            pk: EcPoint::from(ProjectivePoint::mul_by_generator(w.as_scalar_ref())),
+            pk: exponentiate_gen(w.as_scalar_ref()),
             w,
         }
     }