openssl_dh_compute_key Computes shared secret for public value of remote DH public key and local DH key &reftitle.description; stringfalseopenssl_dh_compute_key stringpublic_key OpenSSLAsymmetricKeyprivate_key The shared secret returned by openssl_dh_compute_key is often used as an encryption key to secretly communicate with a remote party. This is known as the Diffie-Hellman key exchange. &reftitle.parameters; public_key DH Public key of the remote party. private_key A local DH private key, corresponding to the public key to be shared with the remote party. &reftitle.returnvalues; Returns shared secret on success&return.falseforfailure;. &reftitle.changelog; &Version; &Description; 8.0.0 private_key accepts an OpenSSLAsymmetricKey now; previously, a &resource; of type OpenSSL key was accepted. &reftitle.examples; First generate a public/private DH keypair locally, and have the remote party do the same. We need to use the openssl command-line utility. Next, send your public key to the remote party. Use the openssl pkey command to view the public key you will be sent from the remote party. &example.outputs.similar; Use this public key as a parameter to openssl_dh_compute_key in order to compute the shared secret. ]]> First, generate the DH prime number &example.outputs.similar; Prime and generator values ares passed as p and g into openssl_pkey_new $configargs)); openssl_pkey_export_to_file($private_key,'privatekey.pem',$passphrase='y0urp@s5phr@se'); $details = openssl_pkey_get_details($private_key); $local_pub_key = $details['dh']['pub_key']; echo bin2hex($local_pub_key)."\n";//you can send your public key to the remote party $details = openssl_pkey_get_details(openssl_pkey_get_public("file://remotepublickey.pem")); $remote_public_key = $details['dh']['pub_key']; $shared_secret = openssl_dh_compute_key($remote_public_key, $private_key); echo bin2hex($shared_secret)."\n"; ?> ]]> &reftitle.seealso; openssl_pkey_new openssl_pkey_get_details openssl_pkey_get_private openssl_pkey_get_public