knx/source/ti/drivers/ecdh/ECDHCC26X2.h

/*
 * Copyright (c) 2017-2018, Texas Instruments Incorporated
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/** ============================================================================
 *  @file       ECDHCC26X2.h
 *
 *  @brief      ECDH driver implementation for the CC26X2 family
 *
 *  @warning     This is a beta API. It may change in future releases.
 *
 *  This file should only be included in the board file to fill the ECDH_config
 *  struct.
 *
 *  # Hardware and Implementation Details #
 *
 *  The CC26X2 family has a dedicated public key accelerator.
 *  It is capable of multiple mathematical operations including dedicated ECC point addition, doubling,
 *  and scalar multiplication. Only one operation can be carried out on the accelerator
 *  at a time. Mutual exclusion is implemented at the driver level and coordinated
 *  between all drivers relying on the accelerator. It is transparent to the application
 *  and only noted ensure sensible access timeouts are set.
 *
 *  The large number maths engine (LNME) uses a dedicated 2kB block of RAM (PKA RAM) for its operations.
 *  The operands of the maths operations must be copied into and results out of the PKA ram.
 *  This necessitates a significant number of reads and writes for each operation.
 *  The bus interface to the RAM only allows for word-aligned reads and writes. The CPU splits
 *  the reads and writes from and to general SRAM from unaligned addresses into multiple
 *  bus operations while accumulating the data in a register until it is full.
 *  The result of this hardware process is that providing buffers such as plaintext CryptoKey
 *  keying material to ECC APIs that are word-aligned will significantly speed up the operation and
 *  reduce power consumption.
 *
 *  The driver implementation does not perform runtime checks for most input parameters.
 *  Only values that are likely to have a stochastic element to them are checked (such
 *  as whether a driver is already open). Higher input parameter validation coverage is
 *  achieved by turning on assertions when compiling the driver.
 *
 *  # Supported Curve Types #
 *
 *  The driver implementation supports the following curve types for ECDH:
 *
 *  | Curve Type        | Supported |
 *  |-------------------|-----------|
 *  | Short Weierstrass | Yes       |
 *  | Montgomery        | Yes       |
 *  | Edwards           | No        |
 *
 *  # Curve25519 Private Keys #
 *
 *  When using Montgomery Curve25519, the private key must be formatted according to cr.yp.to/ecdh.html
 *  by the application before passing it to the driver. The driver cannot do so itself as the memory
 *  location of the keying material may be in flash.
 *
 *  For keying material uint8_t myPrivateKey[32], you must do the following:
 *  @code
 *      myPrivateKey[0] &= 0xF8;
 *      myPrivateKey[31] &= 0x7F;
 *      myPrivateKey[31] |= 0x40;
 *  @endcode
 *
 *  Alternatively, you can call ECCParams_FormatCurve25519PrivateKey() in ti/drivers/cryptoutils/ecc/ECCParams.h
 *
 *  # Public Key Validation #
 *
 *  When performing shared secret generation, the foreign public key will always be validated
 *  when using short Weierstrass curves. The only explicitly supported Montgomery curve is
 *  Curve25519 which does not require public key validation.
 *  The implementation assumes that the cofactor, h, of the curve is 1. This lets us
 *  skip the computationally expensive step of multiplying the foreign key by the order and
 *  checking if it yields the point at infinity. When the cofactor is 1, this property is
 *  implied by validating that the point is not already the point at infinity and that it
 *  validates against the curve equation.
 *  All curves supplied by default, the NIST and Brainpool curves, have cofactor = 1. While
 *  the implementation can use arbitrary curves, you should verify that any other curve used
 *  has a cofactor of 1.
 */

#ifndef ti_drivers_ecdh_ECDHCC26X2__include
#define ti_drivers_ecdh_ECDHCC26X2__include

#ifdef __cplusplus
extern "C" {
#endif

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

#include <ti/drivers/Power.h>
#include <ti/drivers/ECDH.h>
#include <ti/drivers/cryptoutils/ecc/ECCParams.h>
#include <ti/drivers/cryptoutils/cryptokey/CryptoKey.h>

#include <ti/devices/DeviceFamily.h>
#include DeviceFamily_constructPath(driverlib/pka.h)

#include <ti/drivers/dpl/HwiP.h>
#include <ti/drivers/dpl/SwiP.h>
#include <ti/drivers/dpl/SemaphoreP.h>

/* Exit the SWI and wait until an HWI call posts the SWI again */
#define ECDHCC26X2_STATUS_FSM_RUN_PKA_OP       ECDH_STATUS_RESERVED - 0
/* Execute the next FSM state immediately without waiting for the next HWI */
#define ECDHCC26X2_STATUS_FSM_RUN_FSM          ECDH_STATUS_RESERVED - 1

/*!
 *  @brief      ECDHCC26X2 states
 *
 *  The ECDH operations are implemented using multiple invidividual
 *  PKA operations. Since state transitions for these operations are almost
 *  always predictable, the state transitions are encoded linearly in this enum.
 *  The FSM controller will increment the state counter and iterate through
 *  states until it is told to stop or restart.
 */
typedef enum ECDHCC26X2_FsmState_ {
    ECDHCC26X2_FSM_ERROR = 0,

    ECDHCC26X2_FSM_GEN_PUB_KEY_VALIDATE_PRIVATE_KEY,
    ECDHCC26X2_FSM_GEN_PUB_KEY_MULT_PRIVATE_KEY_BY_GENERATOR,
    ECDHCC26X2_FSM_GEN_PUB_KEY_MULT_PRIVATE_KEY_BY_GENERATOR_RESULT,
    ECDHCC26X2_FSM_GEN_PUB_KEY_RETURN,

    ECDHCC26X2_FSM_GEN_PUB_KEY_VALIDATE_PRIVATE_KEY_MONTGOMERY,
    ECDHCC26X2_FSM_GEN_PUB_KEY_MULT_PRIVATE_KEY_BY_GENERATOR_MONTGOMERY,
    ECDHCC26X2_FSM_GEN_PUB_KEY_MULT_PRIVATE_KEY_BY_GENERATOR_RESULT_MONTGOMERY,
    ECDHCC26X2_FSM_GEN_PUB_KEY_RETURN_MONTGOMERY,

    ECDHCC26X2_FSM_COMPUTE_SHARED_SECRET_VALIDATE_PUB_KEY,
    ECDHCC26X2_FSM_COMPUTE_SHARED_SECRET_MULT_PRIVATE_KEY_BY_PUB_KEY,
    ECDHCC26X2_FSM_COMPUTE_SHARED_SECRET_MULT_PRIVATE_KEY_BY_PUB_KEY_RESULT,
    ECDHCC26X2_FSM_COMPUTE_SHARED_SECRET_RETURN,

    ECDHCC26X2_FSM_COMPUTE_SHARED_SECRET_MULT_PRIVATE_KEY_BY_PUB_KEY_MONTGOMERY,
    ECDHCC26X2_FSM_COMPUTE_SHARED_SECRET_MULT_PRIVATE_KEY_BY_PUB_KEY_RESULT_MONTGOMERY,
    ECDHCC26X2_FSM_COMPUTE_SHARED_SECRET_RETURN_MONTGOMERY,
} ECDHCC26X2_FsmState;

/*!
 *  @brief      ECDHCC26X2 Hardware Attributes
 *
 *  ECC26XX hardware attributes should be included in the board file
 *  and pointed to by the ECDH_config struct.
 */
typedef struct ECDHCC26X2_HWAttrs_ {
    /*! @brief Crypto Peripheral's interrupt priority.

        The CC26xx uses three of the priority bits, meaning ~0 has the same effect as (7 << 5).

        (7 << 5) will apply the lowest priority.

        (1 << 5) will apply the highest priority.

        Setting the priority to 0 is not supported by this driver.

        HWI's with priority 0 ignore the HWI dispatcher to support zero-latency interrupts, thus invalidating the critical sections in this driver.
    */
    uint8_t    intPriority;
} ECDHCC26X2_HWAttrs;

/*!
 *  @brief      ECDHCC26X2 Object
 *
 *  The application must not access any member variables of this structure!
 */
typedef struct ECDHCC26X2_Object_ {
    bool                            isOpen;
    bool                            operationInProgress;
    bool                            operationCanceled;
    int_fast16_t                    operationStatus;
    ECDH_CallbackFxn                callbackFxn;
    ECDH_ReturnBehavior             returnBehavior;
    ECDH_Operation                  operation;
    ECDH_OperationType              operationType;
    ECDHCC26X2_FsmState             fsmState;
    uint32_t                        semaphoreTimeout;
    uint32_t                        resultAddress;
} ECDHCC26X2_Object;

#ifdef __cplusplus
}
#endif

#endif /* ti_drivers_ecdh_ECDHCC26X2__include */