DH_GENERATE_KEY(3)

NAME
DH_generate_key, DH_compute_key - perform Diffie-Hellman key exchange

SYNOPSIS
#include <openssl/dh.h>
int
DH_generate_key(DH *dh);
int
DH_compute_key(unsigned char *key, BIGNUM *pub_key, DH *dh);

DESCRIPTION
DH_generate_key() performs the first step of a Diffie-Hellman key exchange by generating private and public DH values. By calling DH_compute_key(), these are combined with the other party's public value to compute the shared key.

DH_generate_key() expects dh to contain the shared parameters dh->p and dh->g. It generates a random private DH value unless dh->priv_key is already set, and computes the corresponding public value dh->pub_key, which can then be published.

DH_compute_key() computes the shared secret from the private DH value in dh and the other party's public value in pub_key and stores it in key. key must point to DH_size(dh) bytes of memory.

RETURN VALUES
DH_generate_key() returns 1 on success, or 0 otherwise.

DH_compute_key() returns the size of the shared secret on success, or -1 on error.

The error codes can be obtained by ERR_get_error(3).

SEE ALSO
DH_get0_key(3), DH_new(3), DH_size(3), ERR_get_error(3), RAND_bytes(3)

HISTORY
DH_generate_key() and DH_compute_key() first appeared in SSLeay 0.5.1 and have been available since OpenBSD 2.4.