mod_exp_ibex.h

// Copyright lowRISC contributors (OpenTitan project).
// Licensed under the Apache License, Version 2.0, see LICENSE for details.
// SPDX-License-Identifier: Apache-2.0
 
#ifndef OPENTITAN_SW_DEVICE_SILICON_CREATOR_LIB_SIGVERIFY_MOD_EXP_IBEX_H_
#define OPENTITAN_SW_DEVICE_SILICON_CREATOR_LIB_SIGVERIFY_MOD_EXP_IBEX_H_
 
#include <stdbool.h>
#include <stdint.h>
 
#include "sw/device/silicon_creator/lib/error.h"
#include "sw/device/silicon_creator/lib/sigverify/rsa_key.h"
 
#ifdef __cplusplus
extern "C" {
#endif  // __cplusplus
 
/**
 * Computes the modular exponentiation of an RSA signature on Ibex.
 *
 * Given an RSA public key and sig, this function computes sig^e mod n using
 * Montgomery multiplication, where
 * - sig is an RSA signature,
 * - e and n are the exponent and the modulus of the key, respectively.
 *
 * The key exponent is always 65537; no other exponents are supported.
 *
 * @param key An RSA public key.
 * @param sig Buffer that holds the signature, little-endian.
 * @param result Buffer to write the result to, little-endian.
 * @return The result of the operation.
 */
OT_WARN_UNUSED_RESULT
rom_error_t sigverify_mod_exp_ibex(const sigverify_rsa_key_t *key,
                                   const sigverify_rsa_buffer_t *sig,
                                   sigverify_rsa_buffer_t *result);
 
#ifdef __cplusplus
}  // extern "C"
#endif  // __cplusplus
 
#endif  // OPENTITAN_SW_DEVICE_SILICON_CREATOR_LIB_SIGVERIFY_MOD_EXP_IBEX_H_