Add is_on_curve hint and basic test

Cargo.toml

@@ -14,6 +14,7 @@ indexmap = "1.9.2"
 indoc = "2"
 lazy_static = "1.4.0"
 log = "0.4.19"
+num-bigint = "0.4"
 num-integer = "0.1.45"
 num-traits = "0.2.16"
 regex = "1.10.0"

src/hints/mod.rs

@@ -2,11 +2,10 @@ pub mod block_context;
 pub mod builtins;
 pub mod execution;
 pub mod syscalls;
-mod unimplemented;
-mod vars;
-
 #[cfg(test)]
 mod tests;
+mod unimplemented;
+mod vars;
 
 use std::collections::{HashMap, HashSet};
 
@@ -25,6 +24,7 @@ use cairo_vm::vm::runners::cairo_runner::{ResourceTracker, RunResources};
 use cairo_vm::vm::vm_core::VirtualMachine;
 use cairo_vm::Felt252;
 use indoc::indoc;
+use num_bigint::BigInt;
 
 use crate::config::DEFAULT_INPUT_PATH;
 use crate::io::input::StarknetOsInput;
@@ -37,7 +37,7 @@ type HintImpl = fn(
     &HashMap<String, Felt252>,
 ) -> Result<(), HintError>;
 
-static HINTS: [(&str, HintImpl); 50] = [
+static HINTS: [(&str, HintImpl); 51] = [
     // (BREAKPOINT, breakpoint),
     (STARKNET_OS_INPUT, starknet_os_input),
     (INITIALIZE_STATE_CHANGES, initialize_state_changes),
@@ -88,6 +88,7 @@ static HINTS: [(&str, HintImpl); 50] = [
     (syscalls::SEND_MESSAGE_TO_L1, syscalls::send_message_to_l1),
     (syscalls::STORAGE_READ, syscalls::storage_read),
     (syscalls::STORAGE_WRITE, syscalls::storage_write),
+    (IS_ON_CURVE, is_on_curve),
     (IS_N_GE_TWO, is_n_ge_two),
 ];
 
@@ -355,3 +356,22 @@ pub fn is_n_ge_two(
     insert_value_into_ap(vm, value)?;
     Ok(())
 }
+
+pub const IS_ON_CURVE: &str = "ids.is_on_curve = (y * y) % SECP_P == y_square_int";
+pub fn is_on_curve(
+    vm: &mut VirtualMachine,
+    exec_scopes: &mut ExecutionScopes,
+    ids_data: &HashMap<String, HintReference>,
+    ap_tracking: &ApTracking,
+    _constants: &HashMap<String, Felt252>,
+) -> Result<(), HintError> {
+    let y: BigInt = exec_scopes.get(vars::ids::Y)?;
+    let y_square_int: BigInt = exec_scopes.get(vars::ids::Y_SQUARE_INT)?;
+    let sec_p: BigInt = exec_scopes.get(vars::ids::SECP_P)?;
+
+    let is_on_curve = (y.clone() * y) % sec_p == y_square_int;
+    let is_on_curve: Felt252 = if is_on_curve { Felt252::ONE } else { Felt252::ZERO };
+    insert_value_from_var_name(vars::ids::IS_ON_CURVE, is_on_curve, vm, ids_data, ap_tracking)?;
+
+    Ok(())
+}

src/hints/tests.rs

@@ -2,6 +2,7 @@
 mod tests {
     use cairo_vm::serde::deserialize_program::ApTracking;
     use cairo_vm::types::exec_scope::ExecutionScopes;
+    use num_bigint::BigInt;
     use rstest::rstest;
 
     use crate::hints::*;
@@ -29,6 +30,41 @@ mod tests {
             }
         };
     }
+
+    #[test]
+    fn test_is_on_curve() {
+        let mut vm = VirtualMachine::new(false);
+        vm.set_fp(1);
+        vm.add_memory_segment();
+        vm.add_memory_segment();
+
+        let ids_data = ids_data![vars::ids::IS_ON_CURVE];
+        let ap_tracking = ApTracking::default();
+
+        let mut exec_scopes = ExecutionScopes::new();
+
+        let y = BigInt::from(1234);
+        let y_square_int = y.clone() * y.clone();
+
+        exec_scopes.insert_value(vars::ids::Y, y);
+        exec_scopes.insert_value(vars::ids::Y_SQUARE_INT, y_square_int);
+
+        // TODO: use an appropriate constant for SECP_P. Also see TODO in `fn is_on_curve` -- should it be
+        // in exec_scopes to begin with, or should it implicitly exist in the hint itself?
+        use std::str::FromStr;
+        let secp_p =
+            BigInt::from_str("115792089237316195423570985008687907853269984665640564039457584007908834671663").unwrap();
+        exec_scopes.insert_value(vars::ids::SECP_P, secp_p);
+
+        is_on_curve(&mut vm, &mut exec_scopes, &ids_data, &ap_tracking, &Default::default())
+            .expect("is_on_curve() failed");
+
+        let is_on_curve: Felt252 = get_integer_from_var_name(vars::ids::IS_ON_CURVE, &vm, &ids_data, &ap_tracking)
+            .expect("is_on_curve should be put in ids_data")
+            .into_owned();
+        assert_eq!(is_on_curve, 1.into());
+    }
+
     #[rstest]
     #[case(Felt252::TWO, Felt252::ONE)]
     #[case(Felt252::THREE, Felt252::ONE)]

src/hints/unimplemented.rs

@@ -1,8 +1,5 @@
 use indoc::indoc;
 
-#[allow(unused)]
-const IS_ON_CURVE: &str = "ids.is_on_curve = (y * y) % SECP_P == y_square_int";
-
 #[allow(unused)]
 const CACHE_CONTRACT_STORAGE: &str = indoc! {r#"
 	# Make sure the value is cached (by reading it), to be used later on for the

src/hints/vars.rs

@@ -3,7 +3,11 @@ pub mod scopes {
 }
 
 pub mod ids {
+    pub const IS_ON_CURVE: &str = "is_on_curve";
     pub const OS_CONTEXT: &str = "os_context";
+    pub const SECP_P: &str = "SECP_P";
     pub const SYSCALL_PTR: &str = "syscall_ptr";
+    pub const Y: &str = "y";
+    pub const Y_SQUARE_INT: &str = "y_square_int";
     pub const N: &str = "n";
 }