DH_generate_key 3 2003-07-24 0.9.9-dev OpenSSL

### NAME

DH_generate_key, DH_compute_key - perform Diffie-Hellman key exchange

### LIBRARY

libcrypto, -lcrypto

### SYNOPSIS

     #include

     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, 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(3).

### SEE ALSO

openssl_dh(3), ERR_get_error(3), openssl_rand(3), DH_size(3)

### HISTORY

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