DH_SIZE(3)                 Library Functions Manual                 DH_SIZE(3)

NAME
     DH_size, DH_bits - get Diffie-Hellman prime size

SYNOPSIS
     library "libcrypto"
     #include <openssl/dh.h>

     int
     DH_size(const DH *dh);

     int
     DH_bits(const DH *dh);

DESCRIPTION
     DH_size() returns the Diffie-Hellman prime size in bytes.  It can be used
     to determine how much memory must be allocated for the shared secret
     computed by DH_compute_key(3).

     DH_bits() returns the number of significant bits in the key.

     dh and dh->p must not be NULL.

SEE ALSO
     BN_num_bytes(3), DH_generate_key(3), DH_get0_key(3), DH_new(3),
     DH_security_bits(3)

HISTORY
     DH_size() first appeared in SSLeay 0.5.1 and has been available since
     OpenBSD 2.4.

     DH_bits() first appeared in OpenSSL 1.1.0 and has been available since
     OpenBSD 6.3.

Linux 6.12.107+deb13-amd64       June 8, 2025       Linux 6.12.107+deb13-amd64