- NAME
- SYNOPSIS
- DESCRIPTION
- RETURN VALUES
- SEE ALSO
- HISTORY

# 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, 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.

# SEE ALSO

dh, ERR_get_error, rand, DH_size

# HISTORY

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