[WIP] EC_MUL_INNER hint

Author: jrchatruc

cairo_programs/ec_mul_inner.cairo

@@ -0,0 +1,23 @@
+%builtins range_check
+
+from starkware.cairo.common.cairo_secp.ec import (
+    EcPoint,
+    ec_mul_inner,
+)
+from starkware.cairo.common.cairo_secp.bigint import BigInt3
+
+func main{range_check_ptr: felt}() {
+    // ec_mul_inner
+    let (pow2, res) = ec_mul_inner(
+        EcPoint(
+            BigInt3(65162296, 359657, 04862662171381), BigInt3(-5166641367474701, -63029418, 793)
+        ),
+        123,
+        298,
+    );
+    assert pow2 = EcPoint(
+        BigInt3(30016796425722798916160189, 75045389156830800234717485, 13862403786096360935413684),
+        BigInt3(43820690643633544357415586, 29808113745001228006676979, 15112469502208690731782390),
+    );
+    return ();
+}

pkg/hints/ec_hint.go

@@ -114,3 +114,20 @@ func ecNegateEmbeddedSecpP(virtual_machine vm.VirtualMachine, exec_scopes types.
 	secp_p.Sub(secp_p, big.NewInt(19))
 	return ecNegate(virtual_machine, exec_scopes, ids_data, *secp_p)
 }
+
+/*
+Implements hint:
+%{ memory[ap] = (ids.scalar % PRIME) % 2 %}
+*/
+func ecMulInner(virtualMachine *vm.VirtualMachine, ids hint_utils.IdsManager) error {
+	scalar, err := ids.GetFelt("scalar", virtualMachine)
+
+	if err != nil {
+		return err
+	}
+
+	result := scalar.And(lambdaworks.FeltOne())
+	virtualMachine.Segments.Memory.Insert(virtualMachine.RunContext.Ap, memory.NewMaybeRelocatableFelt(result))
+
+	return nil
+}

pkg/hints/ec_hint_test.go

@@ -128,3 +128,81 @@ func TestRunEcEmbeddedSecpOk(t *testing.T) {
 	}
 
 }
+
+func TestEcMulInnerSuccessEven(t *testing.T) {
+	vm := NewVirtualMachine()
+	vm.Segments.AddSegment()
+	vm.Segments.AddSegment()
+
+	scalar := NewMaybeRelocatableFelt(FeltFromUint64(89712))
+	idsManager := SetupIdsForTest(
+		map[string][]*MaybeRelocatable{
+			"scalar": {scalar},
+		},
+		vm,
+	)
+
+	hintProcessor := CairoVmHintProcessor{}
+
+	hintData := any(HintData{
+		Ids:  idsManager,
+		Code: EC_MUL_INNER,
+	})
+
+	vm.RunContext.Ap = NewRelocatable(1, 1)
+
+	err := hintProcessor.ExecuteHint(vm, &hintData, nil, nil)
+	result, err := vm.Segments.Memory.Get(NewRelocatable(1, 1))
+
+	if err != nil {
+		t.Errorf("EC_MUL_INNER hint failed with error %s", err)
+	}
+
+	resultFelt, ok := result.GetFelt()
+	if !ok {
+		t.Errorf("EC_MUL_INNER hint expected Felt value as result")
+	}
+
+	if !resultFelt.IsZero() {
+		t.Errorf("EC_MUL_INNER should have returned 0 but got %v", resultFelt)
+	}
+}
+
+func TestEcMulInnerSuccessOdd(t *testing.T) {
+	vm := NewVirtualMachine()
+	vm.Segments.AddSegment()
+	vm.Segments.AddSegment()
+
+	scalar := NewMaybeRelocatableFelt(FeltFromUint64(89711))
+	idsManager := SetupIdsForTest(
+		map[string][]*MaybeRelocatable{
+			"scalar": {scalar},
+		},
+		vm,
+	)
+
+	hintProcessor := CairoVmHintProcessor{}
+
+	hintData := any(HintData{
+		Ids:  idsManager,
+		Code: EC_MUL_INNER,
+	})
+
+	vm.RunContext.Ap = NewRelocatable(1, 1)
+
+	err := hintProcessor.ExecuteHint(vm, &hintData, nil, nil)
+	result, err := vm.Segments.Memory.Get(NewRelocatable(1, 1))
+
+	if err != nil {
+		t.Errorf("EC_MUL_INNER hint failed with error %s", err)
+	}
+
+	resultFelt, ok := result.GetFelt()
+	if !ok {
+		t.Errorf("EC_MUL_INNER hint expected Felt value as result")
+	}
+
+	if resultFelt.Cmp(FeltOne()) != 0 {
+		t.Errorf("EC_MUL_INNER should have returned 1 but got %v", resultFelt)
+	}
+}

pkg/hints/hint_codes/ec_op_hints.go

@@ -2,3 +2,4 @@ package hint_codes
 
 const EC_NEGATE = "from starkware.cairo.common.cairo_secp.secp_utils import SECP_P, pack\n\ny = pack(ids.point.y, PRIME) % SECP_P\n# The modulo operation in python always returns a nonnegative number.\nvalue = (-y) % SECP_P"
 const EC_NEGATE_EMBEDDED_SECP = "from starkware.cairo.common.cairo_secp.secp_utils import pack\nSECP_P = 2**255-19\n\ny = pack(ids.point.y, PRIME) % SECP_P\n# The modulo operation in python always returns a nonnegative number.\nvalue = (-y) % SECP_P"
+const EC_MUL_INNER = "memory[ap] = (ids.scalar % PRIME) % 2"

pkg/hints/hint_processor.go

@@ -138,6 +138,8 @@ func (p *CairoVmHintProcessor) ExecuteHint(vm *vm.VirtualMachine, hintData *any,
 		return splitInt(data.Ids, vm)
 	case SPLIT_INT_ASSERT_RANGE:
 		return splitIntAssertRange(data.Ids, vm)
+	case EC_MUL_INNER:
+		return ecMulInner(vm, data.Ids)
 	default:
 		return errors.Errorf("Unknown Hint: %s", data.Code)
 	}

pkg/vm/cairo_run/cairo_run_test.go

@@ -197,3 +197,7 @@ func TestSplitIntHint(t *testing.T) {
 		t.Errorf("Program execution failed with error: %s", err)
 	}
 }
+
+func TestEcMulInner(t *testing.T) {
+	testProgram("ec_mul_inner", t)
+}