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fix(avm): Fix TS ECC add infinity handling #19657

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Merged
sirasistant merged 1 commit into from
Jan 16, 2026
Merged

fix(avm): Fix TS ECC add infinity handling #19657

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34 changes: 34 additions & 0 deletions barretenberg/cpp/src/barretenberg/vm2/simulation/gadgets/ecc.test.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -240,5 +240,39 @@ TEST(AvmSimulationEccTest, InfinityOnCurve)
EXPECT_EQ(result, q);
}

TEST(AvmSimulationEccTest, AddsUpToInfinity)
{
EventEmitter<EccAddEvent> ecc_event_emitter;
EventEmitter<ScalarMulEvent> scalar_mul_event_emitter;
EventEmitter<EccAddMemoryEvent> ecc_add_memory_event_emitter;

StrictMock<MockExecutionIdManager> execution_id_manager;
StrictMock<MockGreaterThan> gt;
StrictMock<MockToRadix> to_radix;
MemoryStore memory;

EXPECT_CALL(execution_id_manager, get_execution_id()).WillOnce(Return(0));
EXPECT_CALL(gt, gt(0x1000 + 2, AVM_HIGHEST_MEM_ADDRESS)).WillOnce(Return(false));

Ecc ecc(
execution_id_manager, gt, to_radix, ecc_event_emitter, scalar_mul_event_emitter, ecc_add_memory_event_emitter);

// Both points on the curve, q = -p
FF p_x("0x04c95d1b26d63d46918a156cae92db1bcbc4072a27ec81dc82ea959abdbcf16a");
FF p_y("0x035b6dd9e63c1370462c74775765d07fc21fd1093cc988149d3aa763bb3dbb60");
EmbeddedCurvePoint p(p_x, p_y, false);

EmbeddedCurvePoint q = -p;

uint32_t dst_address = 0x1000;
ecc.add(memory, p, q, dst_address);

// Zero as coordinates
EXPECT_EQ(memory.get(dst_address).as_ff(), FF(0));
EXPECT_EQ(memory.get(dst_address + 1).as_ff(), FF(0));
// Infinity
EXPECT_EQ(memory.get(dst_address + 2).as_ff(), 1);
}

} // namespace
} // namespace bb::avm2::simulation
141 changes: 141 additions & 0 deletions yarn-project/simulator/src/public/avm/opcodes/ec_add.test.ts
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Expand Up @@ -117,6 +117,147 @@ describe('EC Instructions', () => {
expect(actual).toEqual(G3);
expect(context.machineState.memory.get(8).toFr().equals(Fr.ZERO)).toBe(true);
});

it('Should add correctly with rhs being infinity', async () => {
const zero = new Uint1(0);
const one = new Uint1(1);

const x = new Field(Grumpkin.generator.x);
const y = new Field(Grumpkin.generator.y);

// Point 1 is not infinity
context.machineState.memory.set(0, x);
context.machineState.memory.set(1, y);
context.machineState.memory.set(2, zero);
// Point 2 is infinity
context.machineState.memory.set(3, x);
context.machineState.memory.set(4, y);
context.machineState.memory.set(5, one);
context.machineState.memory.set(6, new Uint32(6));

await new EcAdd(
/*addressing_mode=*/ 0,
/*p1X=*/ 0,
/*p1Y=*/ 1,
/*p1IsInfinite=*/ 2,
/*p2X=*/ 3,
/*p2Y=*/ 4,
/*p2IsInfinite=*/ 5,
/*dstOffset=*/ 6,
).execute(context);

expect([
context.machineState.memory.get(6).toFr(),
context.machineState.memory.get(7).toFr(),
context.machineState.memory.get(8).toNumber(),
]).toEqual([x.toFr(), y.toFr(), 0]);
});

it('Should add correctly with lhs being infinity', async () => {
const zero = new Uint1(0);
const one = new Uint1(1);

const x = new Field(Grumpkin.generator.x);
const y = new Field(Grumpkin.generator.y);

// Point 1 is infinity
context.machineState.memory.set(0, x);
context.machineState.memory.set(1, y);
context.machineState.memory.set(2, one);
// Point 2 is not infinity
context.machineState.memory.set(3, x);
context.machineState.memory.set(4, y);
context.machineState.memory.set(5, zero);
context.machineState.memory.set(6, new Uint32(6));

await new EcAdd(
/*addressing_mode=*/ 0,
/*p1X=*/ 0,
/*p1Y=*/ 1,
/*p1IsInfinite=*/ 2,
/*p2X=*/ 3,
/*p2Y=*/ 4,
/*p2IsInfinite=*/ 5,
/*dstOffset=*/ 6,
).execute(context);

expect([
context.machineState.memory.get(6).toFr(),
context.machineState.memory.get(7).toFr(),
context.machineState.memory.get(8).toNumber(),
]).toEqual([x.toFr(), y.toFr(), 0]);
});

it('Should add correctly with both being infinity', async () => {
const one = new Uint1(1);

const x = new Field(Grumpkin.generator.x);
const y = new Field(Grumpkin.generator.y);

// Point 1 is infinity
context.machineState.memory.set(0, x);
context.machineState.memory.set(1, y);
context.machineState.memory.set(2, one);
// Point 2 is infinity
context.machineState.memory.set(3, x);
context.machineState.memory.set(4, y);
context.machineState.memory.set(5, one);
context.machineState.memory.set(6, new Uint32(6));

await new EcAdd(
/*addressing_mode=*/ 0,
/*p1X=*/ 0,
/*p1Y=*/ 1,
/*p1IsInfinite=*/ 2,
/*p2X=*/ 3,
/*p2Y=*/ 4,
/*p2IsInfinite=*/ 5,
/*dstOffset=*/ 6,
).execute(context);

expect([
context.machineState.memory.get(6).toFr(),
context.machineState.memory.get(7).toFr(),
context.machineState.memory.get(8).toNumber(),
]).toEqual([Fr.ZERO, Fr.ZERO, 1]);
});

it('Should add correctly with none infinity adding up to infinity', async () => {
const zero = new Uint1(0);

// Point 1 is a "random" point on the curve
const x1 = new Field(2165030248772332382647339664685760681662697934905450801078761197378150920554n);
const y1 = new Field(1518479793551399970960577643223827307749147426195887130444945641264602004320n);
// Point 2 is negation of point 1
const x2 = new Field(2165030248772332382647339664685760681662697934905450801078761197378150920554n);
const y2 = new Field(20369763078287875251285828102033447780799216974220147213253258545311206491297n);

context.machineState.memory.set(0, x1);
context.machineState.memory.set(1, y1);
context.machineState.memory.set(2, zero);

context.machineState.memory.set(3, x2);
context.machineState.memory.set(4, y2);
context.machineState.memory.set(5, zero);
context.machineState.memory.set(6, new Uint32(6));

await new EcAdd(
/*addressing_mode=*/ 0,
/*p1X=*/ 0,
/*p1Y=*/ 1,
/*p1IsInfinite=*/ 2,
/*p2X=*/ 3,
/*p2Y=*/ 4,
/*p2IsInfinite=*/ 5,
/*dstOffset=*/ 6,
).execute(context);

expect([
context.machineState.memory.get(6).toFr(),
context.machineState.memory.get(7).toFr(),
context.machineState.memory.get(8).toNumber(),
]).toEqual([Fr.ZERO, Fr.ZERO, 1]);
});
});

describe('EcAdd should throw an error when a point is not on the curve', () => {
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13 changes: 11 additions & 2 deletions yarn-project/simulator/src/public/avm/opcodes/ec_add.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -79,12 +79,21 @@ export class EcAdd extends Instruction {
}

let dest;
if (p1IsInfinite) {
if (p1IsInfinite && p2IsInfinite) {
dest = Point.ZERO;

@MirandaWood MirandaWood Jan 16, 2026

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Ahh, I see why this all failed previously... Point.ZERO is not really the point at infinity (the Point class stores isInfinite = false for ZERO, which is never passed to bb anyway). Maybe tracking a destIsInfinite in this nested if would be better so we can override more robustly at the end?
Anyway! This is great for now, good find!!

@sirasistant sirasistant Jan 16, 2026

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yeah wanted to do a minimal fix since it's on the old ts codebase

} else if (p1IsInfinite) {
dest = p2;
} else if (p2IsInfinite) {
dest = p1;
} else {
dest = await Grumpkin.add(p1, p2);
// TS<>BB ecc add communication is broken for points that add up to infinity.
// However, here we know that both points are on the curve, and that none is infinity
// so we can check for the case where you add p + (-p) = infinity.
if (p1.x.equals(p2.x) && !p1.y.equals(p2.y)) {
dest = Point.ZERO;
} else {
dest = await Grumpkin.add(p1, p2);
}
}

// Important to use setSlice() and not set() in the two following statements as
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