From 11f1626ecc9b0761910b8dfb5465113d834153d5 Mon Sep 17 00:00:00 2001
From: Paul Miller <paul@paulmillr.com>
Date: Mon, 27 Feb 2023 18:41:23 +0000
Subject: [PATCH] modular: Add comment. Add benchmark

---
 benchmark/modular.js    | 10 ++++++++++
 src/abstract/modular.ts |  1 +
 2 files changed, 11 insertions(+)
 create mode 100644 benchmark/modular.js

diff --git a/benchmark/modular.js b/benchmark/modular.js
new file mode 100644
index 0000000..5f4234b
--- /dev/null
+++ b/benchmark/modular.js
@@ -0,0 +1,10 @@
+import { run, mark } from 'micro-bmark';
+import { secp256k1 } from '../secp256k1.js';
+
+run(async () => {
+  console.log(`\x1b[36mmodular, secp256k1 field\x1b[0m`);
+  const { Fp } = secp256k1.CURVE;
+  await mark('invert a', 30000, () => Fp.inv(2n ** 232n - 5910n));
+  await mark('invert b', 30000, () => Fp.inv(2n ** 231n - 5910n));
+  await mark('sqrt', 15000, () => Fp.sqrt(2n ** 231n - 5910n));
+});
diff --git a/src/abstract/modular.ts b/src/abstract/modular.ts
index 0ded40b..5b50a3f 100644
--- a/src/abstract/modular.ts
+++ b/src/abstract/modular.ts
@@ -56,6 +56,7 @@ export function invert(number: bigint, modulo: bigint): bigint {
     throw new Error(`invert: expected positive integers, got n=${number} mod=${modulo}`);
   }
   // Eucledian GCD https://brilliant.org/wiki/extended-euclidean-algorithm/
+  // Fermat's little theorem "CT-like" version inv(n) = n^(m-2) mod m is 30x slower.
   let a = mod(number, modulo);
   let b = modulo;
   // prettier-ignore