Add ristretto multiply syscall (#12699)

programs/bpf/rust/ristretto/src/lib.rs

@@ -0,0 +1,31 @@
+//! @brief Example Rust-based BPF program that performs a ristretto multiply
+
+pub mod ristretto;
+
+extern crate solana_sdk;
+use crate::ristretto::ristretto_mul;
+use curve25519_dalek::{constants::RISTRETTO_BASEPOINT_POINT, scalar::Scalar};
+use solana_sdk::{
+    account_info::AccountInfo, entrypoint, entrypoint::ProgramResult, info, pubkey::Pubkey,
+};
+
+entrypoint!(process_instruction);
+fn process_instruction(
+    _program_id: &Pubkey,
+    _accounts: &[AccountInfo],
+    _instruction_data: &[u8],
+) -> ProgramResult {
+    info!("Ristretto multiply");
+
+    let point = RISTRETTO_BASEPOINT_POINT;
+    let scalar = Scalar::zero();
+    let result = ristretto_mul(&point, &scalar)?;
+    assert_ne!(point, result);
+
+    let point = RISTRETTO_BASEPOINT_POINT;
+    let scalar = Scalar::one();
+    let result = ristretto_mul(&point, &scalar)?;
+    assert_eq!(point, result);
+
+    Ok(())
+}