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openssl_pkey_new

(PHP 4 >= 4.2.0, PHP 5, PHP 7, PHP 8)

openssl_pkey_new — 新規に秘密鍵を生成する

説明

openssl_pkey_new(?array $options = null): OpenSSLAsymmetricKey|false

openssl_pkey_new() は、新しい秘密鍵を生成します。鍵の公開部を取得する方法は、以下の例に示します。

注意: この関数を正しく動作させるには、正しい形式の openssl.cnf をインストールしておく必要があります。詳細な情報は、インストールについてのセクションを参照ください。

パラメータ

options: 鍵の作成方法の詳細（ビット数など）を指定するには、 options を使用します。 options の詳細な情報については openssl_csr_new() を参照ください。

戻り値

成功した場合に、OpenSSLAsymmetricKey クラスのインスタンスを返します。エラー時に false を返します。

変更履歴

バージョン	説明
8.0.0	成功した場合に、この関数は OpenSSLAsymmetricKey クラスのインスタンスを返すようになりました。これより前のバージョンでは、 `OpenSSL key` 型のリソースを返していました。
7.1.0	EC キーを作成できるようにするため、 options に `curve_name` が追加されました。

例

例1 秘密鍵から、公開鍵を取得する

<?php
$private_key = openssl_pkey_new();
$public_key_pem = openssl_pkey_get_details($private_key)['key'];
echo $public_key_pem;
$public_key = openssl_pkey_get_public($public_key_pem);
var_dump($public_key);
?>

上の例の出力は、たとえば以下のようになります。

-----BEGIN PUBLIC KEY-----
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEArZFsmN2P6rx1Xt7YV95o
gcdlal0k3ryiIhFNzjwtRNNTXfEfBr6lUuaIJYQ8/XqEBX0hpcfuuF6tTRlonA3t
WLME0QFD93YVsAaXcy76YqjjqcRRodIBphAbYyyMI/lXkQAdn7kbAmr7neSOsMYJ
El9Wo4Hl4oG6e52ZnYHyqW9dxh4hX93eupR2TmcCdVf+r9xoHewP0KJYSHt7vDUX
AQlWYcQiWHIadFsmL0orr6mutlXFReoHbesgKY9/3YLOu0JfxflSjIZ2JeL1NTl1
MsmODsUwgAUrwnWKKx+eQUP5g3GnSB3dPkRh9zRVRiLNWbCugyjrf3e6DgQWrW7j
pwIDAQAB
-----END PUBLIC KEY-----
resource(5) of type (OpenSSL key)

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User Contributed Notes 10 notes

down

dirt at awoms dot com ¶

11 years ago


Working example:

$config = array(
    "digest_alg" => "sha512",
    "private_key_bits" => 4096,
    "private_key_type" => OPENSSL_KEYTYPE_RSA,
);
    
// Create the private and public key
$res = openssl_pkey_new($config);

// Extract the private key from $res to $privKey
openssl_pkey_export($res, $privKey);

// Extract the public key from $res to $pubKey
$pubKey = openssl_pkey_get_details($res);
$pubKey = $pubKey["key"];

$data = 'plaintext data goes here';

// Encrypt the data to $encrypted using the public key
openssl_public_encrypt($data, $encrypted, $pubKey);

// Decrypt the data using the private key and store the results in $decrypted
openssl_private_decrypt($encrypted, $decrypted, $privKey);

echo $decrypted;

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gomez dot alejandre at gmail dot com ¶

6 years ago


Not forget the $configArgs for windows users :D, or the method throws a error with the primary key

//write your configurations :D
$configargs = array(
  "config" => "C:/xampp/php/extras/openssl/openssl.cnf",
  'private_key_bits'=> 2048,
  'default_md' => "sha256",
);

// Create the keypair
$res=openssl_pkey_new($configargs);
// Get private key
openssl_pkey_export($res, $privKey,NULL,$configargs);

and it's for all methods ._ .

a full implementation example here.

https://gist.github.com/DuckHunter213/269a0efd17e709f7f1f177ae7da46ad1

this error take me 3 full days you'r welcome :)

down

scott at brynen dot com ¶

9 years ago


If you try and generate a new key using openssl_pkey_new(), and need to specify the size of the key, the key MUST be type-bound to integer

// works
$keysize = 1024;
$ssl = openssl_pkey_new (array('private_key_bits' => $keysize));

// fails
$keysize = "1024";
$ssl = openssl_pkey_new (array('private_key_bits' => $keysize));

// works (force to int)
$keysize = "1024";
$ssl = openssl_pkey_new (array('private_key_bits' => (int)$keysize));

down

Andrew ¶

3 years ago


It's not documented here but you can also create ECC keys from existing key parameters (e.g. from JWK):

<?php
$key = openssl_pkey_new([
    'ec' => [
        'curve_name' => 'prime256v1',
        'x' => $someXValue,
        'y' => $someYValue,
        'd' => $someDValue
    ]
]);
?>

You can just provide x/y if it's a public key, or you can just provide d if it's a private key.

down

Brad ¶

16 years ago


It's easier than all that, if you just want the keys:

<?php
// Create the keypair
$res=openssl_pkey_new();

// Get private key
openssl_pkey_export($res, $privkey);

// Get public key
$pubkey=openssl_pkey_get_details($res);
$pubkey=$pubkey["key"];
?>

down

Jan ¶

5 years ago


In case this function returns false, then check your openssl.cnf and make sure that in the [req] section of this file the entry default_bits is not commented out.

down

-1

dodginess at yahoo dot com ¶

7 years ago


If you're using openssl_pkey_new() in conjunction with openssl_csr_new() and want to change the CSR digest algorithm as well as specify a custom key size, the configuration override should be defined once and sent to both functions:

<?php
$config = array(
    'digest_alg' => 'sha1',
    'private_key_bits' => 2048,
    'private_key_type' => OPENSSL_KEYTYPE_RSA,
);

$privkey = openssl_pkey_new($config);

$csr = openssl_csr_new($dn, $privkey, $config);
?>

Although openssl_pkey_new() will accept the 'digest_alg' argument it won't use it, and setting the value has no effect unless you also set this value for openssl_csr_new(). The reason for this is that the $config array is acting as a drop-in replacement for the values found in the openssl.cnf file, so it must contain all of the override values that you need even if the function they're being sent to won't use them.

Also, if you change the 'digest_alg' to something like 'sha256' and still get an MD5 signed CSR check your openssl.cnf file to see whether the digest algorithm you want to use is actually supported.

down

-8

NOSPAM dot alchaemist at hiperlinux dot com dot ar ¶

20 years ago


As you probably found, getting the public key is not as direct as you might think with this documentation.

You can easily get into messages like:

Warning: openssl_pkey_get_public(): Don't know how to get public key from this private key (the documentation lied) in D:\www\keys.php on line 4

The correct steps to get the whole thing seem to be these:

<?
$dn = array("countryName" => 'XX', "stateOrProvinceName" => 'State', "localityName" => 'SomewhereCity', "organizationName" => 'MySelf', "organizationalUnitName" => 'Whatever', "commonName" => 'mySelf', "emailAddress" => 'user@domain.com');
$privkeypass = '1234';
$numberofdays = 365;

$privkey = openssl_pkey_new();
$csr = openssl_csr_new($dn, $privkey);
$sscert = openssl_csr_sign($csr, null, $privkey, $numberofdays);
openssl_x509_export($sscert, $publickey);
openssl_pkey_export($privkey, $privatekey, $privkeypass);
openssl_csr_export($csr, $csrStr);

echo $privatekey; // Will hold the exported PriKey
echo $publickey;  // Will hold the exported PubKey
echo $csrStr;     // Will hold the exported Certificate
?>

Now all you need to do is to make some research on each individual function.

down

-23

zelnaga at gmail dot com ¶

12 years ago


Getting the public key corresponding to a particular private key, through the methods provided for by OpenSSL, is a bit cumbersome. An easier way to do it is to use phpseclib, a pure PHP RSA implementation:

<?php
include('Crypt/RSA.php');

$rsa = new Crypt_RSA();
$rsa->loadKey('...');

$privatekey = $rsa->getPrivateKey();
$publickey = $rsa->getPublicKey();
?>

Doesn't require any extensions be installed.  It'll use bcmath or gmp if they're available, for speed, but doesn't even require those.

down

-12

jthijssen at notloxic dot nl ¶

13 years ago


If you want to change the default private key size (1024) too something else you can use the following code:
 
<?php 
$config = array('private_key_bits' => 512);
$privKey = openssl_pkey_new($config);

?>

Mind though that the minimum number of bits is 384. Any lower will trigger an error.

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