Implement GET_POINT_FROM_X hint

Makefile

@@ -4,7 +4,7 @@
 CAIRO_VM_CLI:=cairo-vm/target/release/cairo-vm-cli
 
 $(CAIRO_VM_CLI):
-	git clone --depth 1 -b v0.8.5 https://github.com/lambdaclass/cairo-vm
+	git clone --depth 1 -b v0.8.7 https://github.com/lambdaclass/cairo-vm
 	cd cairo-vm; cargo b --release --bin cairo-vm-cli
 
 # Create proof mode programs. 

cairo_programs/signature.cairo

@@ -0,0 +1,24 @@
+%builtins range_check
+
+from starkware.cairo.common.cairo_secp.signature import div_mod_n, get_point_from_x
+from starkware.cairo.common.cairo_secp.bigint import BigInt3
+
+func main{range_check_ptr: felt}() {
+    let a: BigInt3 = BigInt3(100, 99, 98);
+    let b: BigInt3 = BigInt3(10, 9, 8);
+    let (res) = div_mod_n(a, b);
+    assert res.d0 = 3413472211745629263979533;
+    assert res.d1 = 17305268010345238170172332;
+    assert res.d2 = 11991751872105858217578135;
+
+    let x: BigInt3 = BigInt3(100, 99, 98);
+    let v: felt = 10;
+    let (point) = get_point_from_x(x, v);
+    assert point.x.d0 = 100;
+    assert point.x.d1 = 99;
+    assert point.x.d2 = 98;
+    assert point.y.d0 = 50471654703173585387369794;
+    assert point.y.d1 = 68898944762041070370364387;
+    assert point.y.d2 = 16932612780945290933872774;
+    return ();
+}

pkg/hints/hint_codes/signature_hint_codes.go

@@ -19,3 +19,15 @@ const DIV_MOD_N_SAFE_DIV = "value = k = safe_div(res * b - a, N)"
 const DIV_MOD_N_SAFE_DIV_PLUS_ONE = "value = k_plus_one = safe_div(res * b - a, N) + 1"
 
 const XS_SAFE_DIV = "value = k = safe_div(res * s - x, N)"
+
+const GET_POINT_FROM_X = `from starkware.cairo.common.cairo_secp.secp_utils import SECP_P, pack
+
+x_cube_int = pack(ids.x_cube, PRIME) % SECP_P
+y_square_int = (x_cube_int + ids.BETA) % SECP_P
+y = pow(y_square_int, (SECP_P + 1) // 4, SECP_P)
+
+# We need to decide whether to take y or SECP_P - y.
+if ids.v % 2 == y % 2:
+    value = y
+else:
+    value = (-y) % SECP_P`

pkg/hints/hint_processor.go

@@ -199,6 +199,8 @@ func (p *CairoVmHintProcessor) ExecuteHint(vm *vm.VirtualMachine, hintData *any,
 		return divModNSafeDiv(data.Ids, execScopes, "a", "b", false)
 	case DIV_MOD_N_SAFE_DIV_PLUS_ONE:
 		return divModNSafeDiv(data.Ids, execScopes, "a", "b", true)
+	case GET_POINT_FROM_X:
+		return getPointFromX(data.Ids, vm, execScopes, constants)
 	case VERIFY_ZERO_EXTERNAL_SECP:
 		return verifyZeroWithExternalConst(*vm, *execScopes, data.Ids)
 	case FAST_EC_ADD_ASSIGN_NEW_X:

pkg/hints/signature_hints.go

@@ -4,6 +4,7 @@ import (
 	"math/big"
 
 	. "github.com/lambdaclass/cairo-vm.go/pkg/hints/hint_utils"
+	. "github.com/lambdaclass/cairo-vm.go/pkg/lambdaworks"
 	. "github.com/lambdaclass/cairo-vm.go/pkg/types"
 	"github.com/lambdaclass/cairo-vm.go/pkg/utils"
 	. "github.com/lambdaclass/cairo-vm.go/pkg/vm"
@@ -82,3 +83,33 @@ func divModNSafeDiv(ids IdsManager, scopes *ExecutionScopes, aAlias string, bAli
 	scopes.AssignOrUpdateVariable("value", *value)
 	return nil
 }
+
+func getPointFromX(ids IdsManager, vm *VirtualMachine, scopes *ExecutionScopes, constants *map[string]Felt) error {
+	// Handle scope & ids variables
+	secpP := SECP_P()
+	scopes.AssignOrUpdateVariable("SECP_P", secpP)
+	betaFelt, err := ids.GetConst("BETA", constants)
+	if err != nil {
+		return err
+	}
+	beta := new(big.Int).Mod(betaFelt.ToBigInt(), &secpP)
+	xCubeIntUnpacked, err := Uint384FromVarName("x_cube", ids, vm)
+	if err != nil {
+		return err
+	}
+	xCube := xCubeIntUnpacked.Pack86()
+	vFelt, err := ids.GetFelt("v", vm)
+	v := vFelt.ToBigInt()
+	if err != nil {
+		return err
+	}
+	// Hint logic
+	yCube := new(big.Int).Mod(new(big.Int).Add(&xCube, beta), &secpP)
+	// y = (yCube ** ((SECP_P + 1) << 2)) % SECP_P
+	y := new(big.Int).Exp(yCube, new(big.Int).Rsh(new(big.Int).Add(&secpP, big.NewInt(1)), 2), &secpP)
+	if utils.IsEven(v) != utils.IsEven(y) {
+		y = new(big.Int).Sub(&secpP, y)
+	}
+	scopes.AssignOrUpdateVariable("value", *y)
+	return nil
+}

pkg/hints/signature_hints_test.go

@@ -157,3 +157,79 @@ func TestDivModSafeDivPlusOneOk(t *testing.T) {
 		t.Error("Wrong/No scope value val")
 	}
 }
+
+func TestGetPointFromXOk(t *testing.T) {
+	vm := NewVirtualMachine()
+	vm.Segments.AddSegment()
+	idsManager := SetupIdsForTest(
+		map[string][]*MaybeRelocatable{
+			"v": {
+				NewMaybeRelocatableFelt(FeltFromUint(18)),
+			},
+			"x_cube": {
+				NewMaybeRelocatableFelt(FeltFromUint64(2147483647)),
+				NewMaybeRelocatableFelt(FeltFromUint64(2147483647)),
+				NewMaybeRelocatableFelt(FeltFromUint64(2147483647)),
+			},
+		},
+		vm,
+	)
+	constants := SetupConstantsForTest(map[string]Felt{
+		"BETA": FeltFromUint(7),
+	}, &idsManager)
+	hintProcessor := CairoVmHintProcessor{}
+	hintData := any(HintData{
+		Ids:  idsManager,
+		Code: GET_POINT_FROM_X,
+	})
+	scopes := NewExecutionScopes()
+	err := hintProcessor.ExecuteHint(vm, &hintData, &constants, scopes)
+	if err != nil {
+		t.Errorf("GET_POINT_FROM_X hint test failed with error %s", err)
+	}
+	// Check result in scope
+	expectedValue, _ := new(big.Int).SetString("21517397797248348844406833268402983856262903417026833897388175962266357959124", 10)
+
+	value, err := FetchScopeVar[big.Int]("value", scopes)
+	if err != nil || value.Cmp(expectedValue) != 0 {
+		t.Errorf("Wrong/No scope var value.\n Expected %v, got: %v", expectedValue, &value)
+	}
+}
+
+func TestGetPointFromXNegativeY(t *testing.T) {
+	vm := NewVirtualMachine()
+	vm.Segments.AddSegment()
+	idsManager := SetupIdsForTest(
+		map[string][]*MaybeRelocatable{
+			"v": {
+				NewMaybeRelocatableFelt(FeltOne()),
+			},
+			"x_cube": {
+				NewMaybeRelocatableFelt(FeltFromUint64(2147483647)),
+				NewMaybeRelocatableFelt(FeltFromUint64(2147483647)),
+				NewMaybeRelocatableFelt(FeltFromUint64(2147483647)),
+			},
+		},
+		vm,
+	)
+	constants := SetupConstantsForTest(map[string]Felt{
+		"BETA": FeltFromUint(7),
+	}, &idsManager)
+	hintProcessor := CairoVmHintProcessor{}
+	hintData := any(HintData{
+		Ids:  idsManager,
+		Code: GET_POINT_FROM_X,
+	})
+	scopes := NewExecutionScopes()
+	err := hintProcessor.ExecuteHint(vm, &hintData, &constants, scopes)
+	if err != nil {
+		t.Errorf("GET_POINT_FROM_X hint test failed with error %s", err)
+	}
+	// Check result in scope
+	expectedValue, _ := new(big.Int).SetString("94274691440067846579164151740284923997007081248613730142069408045642476712539", 10)
+
+	value, err := FetchScopeVar[big.Int]("value", scopes)
+	if err != nil || value.Cmp(expectedValue) != 0 {
+		t.Errorf("Wrong/No scope var value.\n Expected %v, got: %v", expectedValue, &value)
+	}
+}

pkg/utils/math_utils.go

@@ -102,6 +102,11 @@ func Igcdex(a *big.Int, b *big.Int) (*big.Int, *big.Int, *big.Int) {
 	}
 }
 
+func IsEven(n *big.Int) bool {
+	res := new(big.Int).And(n, big.NewInt(1))
+	return res.Cmp(big.NewInt(0)) != 0
+}
+
 func ISqrt(x *big.Int) (*big.Int, error) {
 	if x.Sign() == -1 {
 		return nil, errors.Errorf("Expected x: %s to be non-negative", x)

pkg/vm/cairo_run/cairo_run_test.go

@@ -333,6 +333,10 @@ func TestDivModN(t *testing.T) {
 	testProgram("div_mod_n", t)
 }
 
+func TestSignature(t *testing.T) {
+	testProgram("signature", t)
+}
+
 func TestEcDoubleAssign(t *testing.T) {
 	testProgram("ec_double_assign", t)
 }