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

The DH_generate_key() function 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. 

The DH_generate_key() function 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. 

The DH_compute_key() function 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.  The key must point to DH_size(dh) bytes of memory. 

RETURN VALUES

The DH_generate_key() function returns 1 on success, 0 otherwise. 

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

The error codes can be obtained from ERR_get_error(). 

HISTORY

The DH_generate_key() and DH_compute_key() functions are available in all versions of SSLeay and OpenSSL. 

SEE ALSO

Functions: dh(3), err(3), rand(3), DH_size(3)