ECDHLPF3SW.h

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/*
 * Copyright (c) 2021-2023, Texas Instruments Incorporated
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
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 *
 * *  Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * *  Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * *  Neither the name of Texas Instruments Incorporated nor the names of
 *    its contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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 */
#ifndef ti_drivers_ecdh_ECDHLPF3SW__include
#define ti_drivers_ecdh_ECDHLPF3SW__include

#include <stdint.h>
#include <stdbool.h>

#include <ti/drivers/ECDH.h>

#include <third_party/ecc/include/lowlevelapi.h>

#ifdef __cplusplus
extern "C" {
#endif

typedef struct
{
    uint8_t dummy;
} ECDHLPF3SW_HWAttrs;

/*
 * Performance of the ECC SW library is scaled via the window size parameter
 * which defines the number of bits of the scalar that will be processed together
 * during the execution of the scalar multiplication. A larger window size
 * will have higher performance at the cost of increased memory consumption.
 * A window size of 3 was selected for the best trade-off of performance and
 * memory consumption. WorkZone size was empirically measured.
 *
 * ---------------------------------------------------
 * |             |    NIST P256    |     X25519      |
 * | Window Size |  WorkZone Size  |  WorkZone Size  |
 * |             |     (words)     |     (words)     |
 * |-------------|-----------------|-----------------|
 * |   2 or 3    |       171       |       198       |
 * |      4      |       225       |       225       |
 * |      5      |       333       |       333       |
 * ---------------------------------------------------
 */
#ifndef ECDHLPF3SW_ECC_WINDOW_SIZE
    #define ECDHLPF3SW_ECC_WINDOW_SIZE 3
#endif

/*
 * ECC Workzone size is based on worst case empirical measurement of ECDH
 * operations on supported curves with the selected window size.
 */
#if (ECDHLPF3SW_ECC_WINDOW_SIZE == 2)
    #error "ECDHLPF3SW_ECC_WINDOW_SIZE of 3 should be used instead of 2"
#elif (ECDHLPF3SW_ECC_WINDOW_SIZE == 3)
    #define ECDHLPF3SW_ECC_WORKZONE_WORDS 198
#elif (ECDHLPF3SW_ECC_WINDOW_SIZE == 4)
    #define ECDHLPF3SW_ECC_WORKZONE_WORDS 225
#elif (ECDHLPF3SW_ECC_WINDOW_SIZE == 5)
    #define ECDHLPF3SW_ECC_WORKZONE_WORDS 333
#else
    #error "ECDHLPF3SW_ECC_WINDOW_SIZE is invalid"
#endif

typedef struct
{
    bool isOpen;
    ECDH_ReturnBehavior returnBehavior; /* Callback mode is not supported */
    ECC_State eccState;
    uint32_t eccWorkZone[ECDHLPF3SW_ECC_WORKZONE_WORDS];
} ECDHLPF3SW_Object;

#ifdef __cplusplus
}
#endif

#endif /* ti_drivers_ecdh_ECDHLPF3SW__include */