From 5c9f33cd9f515b5e32c71a73e5b855db78b56a77 Mon Sep 17 00:00:00 2001
From: Gregor <gregor.mitscha-baude@gmx.at>
Date: Tue, 16 Jul 2024 16:02:42 +0200
Subject: [PATCH] don't support small (unsound) curves

---
 src/lib/provable/crypto/foreign-curve.ts   | 12 +++++++++++-
 src/lib/provable/gadgets/elliptic-curve.ts |  7 ++++++-
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/src/lib/provable/crypto/foreign-curve.ts b/src/lib/provable/crypto/foreign-curve.ts
index 323478b87a..1c8ba95be2 100644
--- a/src/lib/provable/crypto/foreign-curve.ts
+++ b/src/lib/provable/crypto/foreign-curve.ts
@@ -11,7 +11,7 @@ import { Field3 } from '../gadgets/foreign-field.js';
 import { assert } from '../gadgets/common.js';
 import { Provable } from '../provable.js';
 import { provableFromClass } from '../types/provable-derivers.js';
-import { multiRangeCheck } from '../gadgets/range-check.js';
+import { l2Mask, multiRangeCheck } from '../gadgets/range-check.js';
 
 // external API
 export {
@@ -307,6 +307,11 @@ class ForeignCurveV2 extends ForeignCurve {
  * @deprecated `createForeignCurve` is now deprecated and will be removed in a future release. Please use {@link createForeignCurveV2} instead.
  */
 function createForeignCurve(params: CurveParams): typeof ForeignCurve {
+  assert(
+    params.modulus > l2Mask + 1n,
+    'Base field moduli smaller than 2^176 are not supported'
+  );
+
   const FieldUnreduced = createForeignField(params.modulus);
   const ScalarUnreduced = createForeignField(params.order);
   class Field extends FieldUnreduced.AlmostReduced {}
@@ -343,6 +348,11 @@ function createForeignCurve(params: CurveParams): typeof ForeignCurve {
  * {@link ForeignCurveV2} also includes to associated foreign fields: `ForeignCurve.Field` and `ForeignCurve.Scalar`, see {@link createForeignFieldV2}.
  */
 function createForeignCurveV2(params: CurveParams): typeof ForeignCurveV2 {
+  assert(
+    params.modulus > l2Mask + 1n,
+    'Base field moduli smaller than 2^176 are not supported'
+  );
+
   const FieldUnreduced = createForeignField(params.modulus);
   const ScalarUnreduced = createForeignField(params.order);
   class Field extends FieldUnreduced.AlmostReduced {}
diff --git a/src/lib/provable/gadgets/elliptic-curve.ts b/src/lib/provable/gadgets/elliptic-curve.ts
index afab631f6e..b6888d3187 100644
--- a/src/lib/provable/gadgets/elliptic-curve.ts
+++ b/src/lib/provable/gadgets/elliptic-curve.ts
@@ -3,7 +3,7 @@ import { Field } from '../field.js';
 import { Provable } from '../provable.js';
 import { assert } from './common.js';
 import { Field3, ForeignField, split, weakBound } from './foreign-field.js';
-import { l, l2, multiRangeCheck } from './range-check.js';
+import { l, l2, l2Mask, multiRangeCheck } from './range-check.js';
 import { sha256 } from 'js-sha256';
 import {
   bigIntToBytes,
@@ -65,6 +65,11 @@ function add(p1: Point, p2: Point, Curve: { modulus: bigint }) {
     return Point.from(p3);
   }
 
+  assert(
+    Curve.modulus > l2Mask + 1n,
+    'Base field moduli smaller than 2^176 are not supported'
+  );
+
   // witness and range-check slope, x3, y3
   let witnesses = exists(9, () => {
     let [x1_, x2_, y1_, y2_] = Field3.toBigints(x1, x2, y1, y2);