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dh(3)				    OpenSSL				 dh(3)

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)

0.9.8za				  2014-06-05				 dh(3)

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO

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<https://www.freebsd.org/cgi/man.cgi?query=dh&sektion=3&manpath=FreeBSD+9.3-RELEASE>

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