/*!
    \ingroup Diffie-Hellman

    \brief This function initializes a Diffie-Hellman key for use in
    negotiating a secure secret key with the Diffie-Hellman exchange protocol.

    \return none No returns.

    \param key pointer to the DhKey structure to initialize for use with
    secure key exchanges

    _Example_
    \code
    DhKey key;
    wc_InitDhKey(&key); // initialize DH key
    \endcode

    \sa wc_FreeDhKey
    \sa wc_DhGenerateKeyPair
*/
WOLFSSL_API int wc_InitDhKey(DhKey* key);

/*!
    \ingroup Diffie-Hellman

    \brief This function frees a Diffie-Hellman key after it has been used to
    negotiate a secure secret key with the Diffie-Hellman exchange protocol.

    \return none No returns.

    \param key pointer to the DhKey structure to free

    _Example_
    \code
    DhKey key;
    // initialize key, perform key exchange

    wc_FreeDhKey(&key); // free DH key to avoid memory leaks
    \endcode

    \sa wc_InitDhKey
*/
WOLFSSL_API void wc_FreeDhKey(DhKey* key);

/*!
    \ingroup Diffie-Hellman

    \brief This function generates a public/private key pair based on the
    Diffie-Hellman public parameters, storing the private key in priv and the
    public key in pub. It takes an initialized Diffie-Hellman key and an
    initialized rng structure.

    \return BAD_FUNC_ARG Returned if there is an error parsing one of the
    inputs to this function
    \return RNG_FAILURE_E Returned if there is an error generating a random
    number using rng
    \return MP_INIT_E May be returned if there is an error in the math library
    while generating the public key
    \return MP_READ_E May be returned if there is an error in the math library
    while generating the public key
    \return MP_EXPTMOD_E May be returned if there is an error in the math
    library while generating the public key
    \return MP_TO_E May be returned if there is an error in the math library
    while generating the public key

    \param key pointer to the DhKey structure from which to generate
    the key pair
    \param rng pointer to an initialized random number generator (rng) with
    which to generate the keys
    \param priv pointer to a buffer in which to store the private key
    \param privSz will store the size of the private key written to priv
    \param pub pointer to a buffer in which to store the public key
    \param pubSz will store the size of the private key written to pub

    _Example_
    \code
    DhKey key;
    int ret;
    byte priv[256];
    byte pub[256];
    word32 privSz, pubSz;

    wc_InitDhKey(&key); // initialize key
    // Set DH parameters using wc_DhSetKey or wc_DhKeyDecode
    WC_RNG rng;
    wc_InitRng(&rng); // initialize rng
    ret = wc_DhGenerateKeyPair(&key, &rng, priv, &privSz, pub, &pubSz);
    \endcode

    \sa wc_InitDhKey
    \sa wc_DhSetKey
    \sa wc_DhKeyDecode
*/
WOLFSSL_API int wc_DhGenerateKeyPair(DhKey* key, WC_RNG* rng, byte* priv,
                                 word32* privSz, byte* pub, word32* pubSz);

/*!
    \ingroup Diffie-Hellman

    \brief This function generates an agreed upon secret key based on a local
    private key and a received public key. If completed on both sides of an
    exchange, this function generates an agreed upon secret key for symmetric
    communication. On successfully generating a shared secret key, the size of
    the secret key written will be stored in agreeSz.

    \return 0 Returned on successfully generating an agreed upon secret key
    \return MP_INIT_E May be returned if there is an error while generating
    the shared secret key
    \return MP_READ_E May be returned if there is an error while generating
    the shared secret key
    \return MP_EXPTMOD_E May be returned if there is an error while generating
    the shared secret key
    \return MP_TO_E May be returned if there is an error while generating the
    shared secret key

    \param key pointer to the DhKey structure to use to compute the shared key
    \param agree pointer to the buffer in which to store the secret key
    \param agreeSz will hold the size of the secret key after
    successful generation
    \param priv pointer to the buffer containing the local secret key
    \param privSz size of the local secret key
    \param otherPub pointer to a buffer containing the received public key
    \param pubSz size of the received public key

    _Example_
    \code
    DhKey key;
    int ret;
    byte priv[256];
    byte agree[256];
    word32 agreeSz;

    // initialize key, set key prime and base
    // wc_DhGenerateKeyPair -- store private key in priv
    byte pub[] = { // initialized with the received public key };
    ret = wc_DhAgree(&key, agree, &agreeSz, priv, sizeof(priv), pub,
    sizeof(pub));
    if ( ret != 0 ) {
    	// error generating shared key
    }
    \endcode

    \sa wc_DhGenerateKeyPair
*/
WOLFSSL_API int wc_DhAgree(DhKey* key, byte* agree, word32* agreeSz,
                       const byte* priv, word32 privSz, const byte* otherPub,
                       word32 pubSz);

/*!
    \ingroup Diffie-Hellman

    \brief This function decodes a Diffie-Hellman key from the given input
    buffer containing the key in DER format. It stores the result in the
    DhKey structure.

    \return 0 Returned on successfully decoding the input key
    \return ASN_PARSE_E Returned if there is an error parsing the sequence
    of the input
    \return ASN_DH_KEY_E Returned if there is an error reading the private
    key parameters from the parsed input

    \param input pointer to the buffer containing the DER formatted
    Diffie-Hellman key
    \param inOutIdx pointer to an integer in which to store the index parsed
    to while decoding the key
    \param key pointer to the DhKey structure to initialize with the input key
    \param inSz length of the input buffer. Gives the max length that may
    be read

    _Example_
    \code
    DhKey key;
    word32 idx = 0;

    byte keyBuff[1024];
    // initialize with DER formatted key
    wc_DhKeyInit(&key);
    ret = wc_DhKeyDecode(keyBuff, &idx, &key, sizeof(keyBuff));

    if ( ret != 0 ) {
    	// error decoding key
    }
    \endcode

    \sa wc_DhSetKey
*/
WOLFSSL_API int wc_DhKeyDecode(const byte* input, word32* inOutIdx, DhKey* key,
                           word32);

/*!
    \ingroup Diffie-Hellman

    \brief This function sets the key for a DhKey structure using the input
    private key parameters. Unlike wc_DhKeyDecode, this function does not
    require that the input key be formatted in DER format, and instead simply
    accepts the parsed input parameters p (prime) and g (base).

    \return 0 Returned on successfully setting the key
    \return BAD_FUNC_ARG Returned if any of the input parameters
    evaluate to NULL
    \return MP_INIT_E Returned if there is an error initializing the key
    parameters for storage
    \return ASN_DH_KEY_E Returned if there is an error reading in the
    DH key parameters p and g

    \param key pointer to the DhKey structure on which to set the key
    \param p pointer to the buffer containing the prime for use with the key
    \param pSz length of the input prime
    \param g pointer to the buffer containing the base for use with the key
    \param gSz length of the input base

    _Example_
    \code
    DhKey key;

    byte p[] = { // initialize with prime };
    byte g[] = { // initialize with base };
    wc_DhKeyInit(&key);
    ret = wc_DhSetKey(key, p, sizeof(p), g, sizeof(g));

    if ( ret != 0 ) {
    	// error setting key
    }
    \endcode

    \sa wc_DhKeyDecode
*/
WOLFSSL_API int wc_DhSetKey(DhKey* key, const byte* p, word32 pSz, const byte* g,
                        word32 gSz);

/*!
    \ingroup Diffie-Hellman

    \brief This function loads the Diffie-Hellman parameters, p (prime)
    and g (base) out of the given input buffer, DER formatted.

    \return 0 Returned on successfully extracting the DH parameters
    \return ASN_PARSE_E Returned if an error occurs while parsing the DER
    formatted DH certificate
    \return BUFFER_E Returned if there is inadequate space in p or g to
    store the parsed parameters

    \parma input pointer to a buffer containing a DER formatted
    Diffie-Hellman certificate to parse
    \parma inSz size of the input buffer
    \parma p pointer to a buffer in which to store the parsed prime
    \parma pInOutSz pointer to a word32 object containing the available
    size in the p buffer. Will be overwritten with the number of bytes
    written to the buffer after completing the function call
    \parma g pointer to a buffer in which to store the parsed base
    \parma gInOutSz pointer to a word32 object containing the available size
    in the g buffer. Will be overwritten with the number of bytes written to
    the buffer after completing the function call

    _Example_
    \code
    byte dhCert[] = { initialize with DER formatted certificate };
    byte p[MAX_DH_SIZE];
    byte g[MAX_DH_SIZE];
    word32 pSz = MAX_DH_SIZE;
    word32 gSz = MAX_DH_SIZE;

    ret = wc_DhParamsLoad(dhCert, sizeof(dhCert), p, &pSz, g, &gSz);
    if ( ret != 0 ) {
    	// error parsing inputs
    }
    \endcode

    \sa wc_DhSetKey
    \sa wc_DhKeyDecode
*/
WOLFSSL_API int wc_DhParamsLoad(const byte* input, word32 inSz, byte* p,
                            word32* pInOutSz, byte* g, word32* gInOutSz);

/*!
    \ingroup Diffie-Hellman

    \brief This function returns ... and requires that HAVE_FFDHE_2048 be
    defined.

    \sa wc_Dh_ffdhe3072_Get
    \sa wc_Dh_ffdhe4096_Get
    \sa wc_Dh_ffdhe6144_Get
    \sa wc_Dh_ffdhe8192_Get
*/
WOLFSSL_API const DhParams* wc_Dh_ffdhe2048_Get(void);

/*!
    \ingroup Diffie-Hellman

    \brief This function returns ... and requires that HAVE_FFDHE_3072 be
    defined.

    \sa wc_Dh_ffdhe2048_Get
    \sa wc_Dh_ffdhe4096_Get
    \sa wc_Dh_ffdhe6144_Get
    \sa wc_Dh_ffdhe8192_Get
*/
WOLFSSL_API const DhParams* wc_Dh_ffdhe3072_Get(void);

/*!
    \ingroup Diffie-Hellman

    \brief This function returns ... and requires that HAVE_FFDHE_4096 be
    defined.

    \sa wc_Dh_ffdhe2048_Get
    \sa wc_Dh_ffdhe3072_Get
    \sa wc_Dh_ffdhe6144_Get
    \sa wc_Dh_ffdhe8192_Get
*/
WOLFSSL_API const DhParams* wc_Dh_ffdhe4096_Get(void);

/*!
    \ingroup Diffie-Hellman

    \brief This function returns ... and requires that HAVE_FFDHE_6144 be
    defined.

    \sa wc_Dh_ffdhe2048_Get
    \sa wc_Dh_ffdhe3072_Get
    \sa wc_Dh_ffdhe4096_Get
    \sa wc_Dh_ffdhe8192_Get
*/
WOLFSSL_API const DhParams* wc_Dh_ffdhe6144_Get(void);

/*!
    \ingroup Diffie-Hellman

    \brief This function returns ... and requires that HAVE_FFDHE_8192 be
    defined.

    \sa wc_Dh_ffdhe2048_Get
    \sa wc_Dh_ffdhe3072_Get
    \sa wc_Dh_ffdhe4096_Get
    \sa wc_Dh_ffdhe6144_Get
*/
WOLFSSL_API const DhParams* wc_Dh_ffdhe8192_Get(void);

/*!
    \ingroup Diffie-Hellman

    \brief Checks DH keys for pair-wise consistency per process in SP 800-56Ar3,
    section 5.6.2.1.4, method (b) for FFC.
*/
WOLFSSL_API int wc_DhCheckKeyPair(DhKey* key, const byte* pub, word32 pubSz,
                        const byte* priv, word32 privSz);

/*!
    \ingroup Diffie-Hellman

    \brief Check DH private key for invalid numbers
*/
WOLFSSL_API int wc_DhCheckPrivKey(DhKey* key, const byte* priv, word32 pubSz);

/*!
    \ingroup Diffie-Hellman
*/
WOLFSSL_API int wc_DhCheckPrivKey_ex(DhKey* key, const byte* priv, word32 pubSz,
                            const byte* prime, word32 primeSz);

/*!
    \ingroup Diffie-Hellman
*/
WOLFSSL_API int wc_DhCheckPubKey(DhKey* key, const byte* pub, word32 pubSz);

/*!
    \ingroup Diffie-Hellman
*/
WOLFSSL_API int wc_DhCheckPubKey_ex(DhKey* key, const byte* pub, word32 pubSz,
                            const byte* prime, word32 primeSz);

/*!
    \ingroup Diffie-Hellman
*/
WOLFSSL_API int wc_DhExportParamsRaw(DhKey* dh, byte* p, word32* pSz,
                       byte* q, word32* qSz, byte* g, word32* gSz);

/*!
    \ingroup Diffie-Hellman
*/
WOLFSSL_API int wc_DhGenerateParams(WC_RNG *rng, int modSz, DhKey *dh);

/*!
    \ingroup Diffie-Hellman
*/
WOLFSSL_API int wc_DhSetCheckKey(DhKey* key, const byte* p, word32 pSz,
                        const byte* g, word32 gSz, const byte* q, word32 qSz,
                        int trusted, WC_RNG* rng);

/*!
    \ingroup Diffie-Hellman
*/
WOLFSSL_API int wc_DhSetKey_ex(DhKey* key, const byte* p, word32 pSz,
                        const byte* g, word32 gSz, const byte* q, word32 qSz);

/*!
    \ingroup Diffie-Hellman
*/
WOLFSSL_API int wc_FreeDhKey(DhKey* key);