note 126645 added to function.openssl-dh-compute-key

// Purpose: Provide a working example of Diffie-Hellman, entirely in php. // This function generates a configuration for Diffie-Hellman keypair // We start with an empty config and have openssl_pkey_new create // a prime and a generator. This is a time consuming step. function get_DH_params ($keylength=2048, $digest_alg="sha512") { $pkey = openssl_pkey_new(["digest_alg" => $digest_alg, "private_key_bits" => $keylength, "private_key_type" => OPENSSL_KEYTYPE_DH]); $details = openssl_pkey_get_details($pkey); return [ "digest_alg" => $digest_alg, "private_key_bits" => $keylength, "dh" => array('p' => $details['dh']['p'], 'g' => $details['dh']['g']), "private_key_type" => OPENSSL_KEYTYPE_DH, ]; } // Now Alice and Bob can create their respective keypairs function get_DH_keyPair ($DH_params) { $pkey = openssl_pkey_new($DH_params); $privkey = openssl_pkey_get_private($pkey); $pubkey = openssl_pkey_get_details($pkey)['dh']['pub_key']; return (object) compact('pubkey','privkey'); } // Now Alice and Bob can create a mutual secret function get_DH_mutualsecret($peers_public, $my_private) { return bin2hex(openssl_dh_compute_key($peers_public, $my_private)); } // Usage >>> $dh_params = get_DH_params(); => [ "digest_alg" => "sha512", "private_key_bits" => 2048, "dh" => [ "p" => b"ó»¸'#ð\x18\x04Û_Ä\tõyÁZàx\x15\x14\x11ƒ┬l=Ü┤H\0", "g" => "\x02", ], "private_key_type" => 2, ] // Alice & Bob generate their keys from the same dh_params. // Binary values truncated. >>> $alice = get_DH_keypair($dh_params); => {#3773 +"pubkey": b"""EØüÔSðÔîË╚ùà5ÜLÜ$┘▄±ü6]", +"privkey": OpenSSLAsymmetricKey {#3771}, } >>> $bob = get_DH_keypair($dh_params); => {#3774 +"pubkey": b"'ua¥ªo\ê\x11║OM©\vó╣ßÜWöíþ³e÷:\t9Ô\rB┌\x13", +"privkey": OpenSSLAsymmetricKey {#3765}, } >>> $alice_secret = get_DH_mutualsecret($bob->pubkey, $alice->privkey); => "5fbf9df2f13da103f106. ....." >>> $bob_secret = get_DH_mutualsecret($alice->pubkey, $bob->privkey); => "5fbf9df2f13da103f106. ....." >>> $bob_secret == $alice_secret; => true // Now Alice and Bob have a shared secret which they can use as a symmetric key. The key will be 2048 bits long (same as the DH key length parameter). They can hash it to get a shorter key if they want. // A third person, Charlie, can also create a key pair like Alice and Bob. // And Charlie and Alice can create their own Alice and Bob did. // And Charlie and Bob can create their own (separate) secret. // ---- Server IP: 45.112.84.4 Probable Submitter: 45.112.85.242 (proxied: 73.211.182.136) ---- Manual Page -- https://php.net/manual/en/function.openssl-dh-compute-key.php Edit -- https://main.php.net/note/edit/126645 Del: integrated -- https://main.php.net/note/delete/126645/integrated Del: useless -- https://main.php.net/note/delete/126645/useless Del: bad code -- https://main.php.net/note/delete/126645/bad+code Del: spam -- https://main.php.net/note/delete/126645/spam Del: non-english -- https://main.php.net/note/delete/126645/non-english Del: in docs -- https://main.php.net/note/delete/126645/in+docs Del: other reasons-- https://main.php.net/note/delete/126645 Reject -- https://main.php.net/note/reject/126645 Search -- https://main.php.net/manage/user-notes.php