DH_generate_key, DH_compute_key - perform Diffie-Hellman key exchange
#include <openssl/dh.h> int DH_generate_key(DH *dh); int DH_compute_key(unsigned char *key, BIGNUM *pub_key, DH *dh);
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.
DH_generate_key() returns 1 on success, 0 otherwise.
DH_compute_key() returns the size of the shared secret on success, -1 on error.
The error codes can be obtained by ERR_get_error.
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