dh(3)

NAME
dh - Diffie-Hellman key agreement

SYNOPSIS
 #include <openssl/dh.h>

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

 int    DH_size(DH *dh);

 DH *   DH_generate_parameters(int prime_len, int generator,
                void (*callback)(int, int, void *), void *cb_arg);
 int    DH_check(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(DH_METHOD *meth);
 DH_METHOD *DH_get_default_method(void);
 DH_METHOD *DH_set_method(DH *dh, DH_METHOD *meth);
 DH *DH_new_method(DH_METHOD *meth);
 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(DH *a, unsigned char **pp);

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

DESCRIPTION
These functions implement the Diffie-Hellman key agreement protocol. The generation of shared DH parameters is described in DH_generate_parameters(3); DH_generate_key(3) describes how to perform a key agreement.

The DH structure consists of several BIGNUM components.

 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

SEE ALSO
dhparam(1), bn(3), dsa(3), err(3), rand(3), rsa(3), DH_set_method(3), DH_new(3), DH_get_ex_new_index(3), DH_generate_parameters(3), DH_compute_key(3), d2i_DHparams(3), RSA_print(3)