NAME
dh — Diffie-Hellman key agreement
Synopsis
#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);
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 |
Note that DH keys may use non-standard DH_METHOD implementations,
either directly or by the use of ENGINE modules.
In some cases (eg. an ENGINE providing support for hardware-embedded
keys), these BIGNUM values will not be used by the implementation
or may be used for alternative data storage. For this reason, applications
should generally avoid using DH structure elements directly and
instead use API functions to query or modify keys.
SEE ALSO
dhparam(1), bn(3), dsa(3), err(3), rand(3), rsa(3), engine(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)
