#include <openssl/dh.h>
#include <openssl/engine.h>

DH *    DH_new(void);
void    DH_free(DH *dh);

int     DH_size(const DH *dh);

DH *    DH_generate_parameters(int prime_len, int generator,
                void (*callback)(int, int, void *), void *cb_arg);
int     DH_check(const DH *dh, int *codes);

int     DH_generate_key(DH *dh);
int     DH_compute_key(unsigned char *key, BIGNUM *pub_key, DH *dh);

void DH_set_default_method(const DH_METHOD *meth);
const DH_METHOD *DH_get_default_method(void);
int DH_set_method(DH *dh, const DH_METHOD *meth);
DH *DH_new_method(ENGINE *engine);
const DH_METHOD *DH_OpenSSL(void);

int DH_get_ex_new_index(long argl, char *argp, int (*new_func)(),
             int (*dup_func)(), void (*free_func)());
int DH_set_ex_data(DH *d, int idx, char *arg);
char *DH_get_ex_data(DH *d, int idx);

DH *    d2i_DHparams(DH **a, unsigned char **pp, long length);
int     i2d_DHparams(const DH *a, unsigned char **pp);

int     DHparams_print_fp(FILE *fp, const DH *x);
int     DHparams_print(BIO *bp, const DH *x);

struct
       {
       BIGNUM *p;               // prime number (shared)
       BIGNUM *g;               // generator of Z_p (shared)
       BIGNUM *priv_key;        // private DH value x
       BIGNUM *pub_key; // public DH value g^x
       // ...
       };
DH