Reputation: 66995
How to create uniqe key value in PHP?
How do I create unique key value in PHP?
I need simple unique keys with a length of 20 digits (not more than 33).
Upvotes: 3
Views: 3230
Answers (5)
Reputation: 1806
Code
$rand_val = md5(uniqid() + mt_rand());
Disclaimer
There is a theoretical chance of collision, but not likely. The combination of uniqid and mt_rand() should make it unguessable enough for what ever use there may be. Though this results in a 32 char long string.
(Edited after constructive comments)
Upvotes: 1
Reputation: 95454
You are looking for an encryption key?
Do not use uniqid() in any context where security is involved. It is too predictable to be used in such context.
The PEAR::Crypt_RSA package allows you to generate cryptographically strong keys in PHP. Once installed in your local PEAR install, you may use it to generate a key as follows:
require_once 'Crypt/RSA.php';
// Creates a 96-bit key, which is 24 hex chars long
$key_pair = new Crypt_RSA_KeyPair(96);
//Returns public key from the pair
$public_key = $key_pair->getPublicKey();
//Returns private key from the pair
$private_key = $key_pair->getPrivateKey();
UUID's may also be good for your goal. Here is a class which will generate standard-compliant UUIDs on all systems:
<?php
/**
* UUID generator class
*
* Generates valid RFC 4211 compliant Universally Unique IDentifiers (UUID) version 3, 4 and 5.
* UUIDs generated validate using the OSSP UUID Tool, and the output for named-based UUIDs are
* exactly the same. This is a pure PHP implementation.
*
* Usage:
*
* Name-based UUID:
*
* $v3uuid = UUID::v3('1546058f-5a25-4334-85ae-e68f2a44bbaf', 'SomeRandomString');
* $v5uuid = UUID::v5(UUID::NS_URL, 'http://www.google.com/');
*
* Pseudo-random UUID:
*
* $v4uuid = UUID::v4();
*
*
* Originally found at: http://www.php.net/manual/en/function.uniqid.php#94959
*
* @author Andrew Moore
*
*
* Modifications made by Henry Merriam <[email protected]> on 2009-12-20:
*
* + Added constants for predefined namespaces as defined in RFC 4211 Appendix C.
* + NS_DNS
* + NS_URL
* + NS_ISO_UID
* + NS_X500_DN
*
* + Wrote this documentation comment.
*
*/
class UUID {
const NS_DNS = '6ba7b810-9dad-11d1-80b4-00c04fd430c8'; // FQDN
const NS_URL = '6ba7b811-9dad-11d1-80b4-00c04fd430c8'; // URL
const NS_ISO_OID = '6ba7b812-9dad-11d1-80b4-00c04fd430c8'; // ISO OID
const NS_X500_DN = '6ba7b814-9dad-11d1-80b4-00c04fd430c8'; // X.500 DN (in DER or a text output format)
public static function v3($namespace, $name) {
if(!self::is_valid($namespace)) return false;
// Get hexadecimal components of namespace
$nhex = str_replace(array('-','{','}'), '', $namespace);
// Binary Value
$nstr = '';
// Convert Namespace UUID to bits
for($i = 0; $i < strlen($nhex); $i+=2) {
$nstr .= chr(hexdec($nhex[$i].$nhex[$i+1]));
}
// Calculate hash value
$hash = md5($nstr . $name);
// Format and return UUID
return sprintf('%08s-%04s-%04x-%04x-%12s',
// 32 bits for "time_low"
substr($hash, 0, 8),
// 16 bits for "time_mid"
substr($hash, 8, 4),
// 16 bits for "time_hi_and_version",
// four most significant bits holds version number 3
(hexdec(substr($hash, 12, 4)) & 0x0fff) | 0x3000,
// 16 bits, 8 bits for "clk_seq_hi_res",
// 8 bits for "clk_seq_low",
// two most significant bits holds zero and one for variant DCE1.1
(hexdec(substr($hash, 16, 4)) & 0x3fff) | 0x8000,
// 48 bits for "node"
substr($hash, 20, 12)
);
}
public static function v4() {
return sprintf('%04x%04x-%04x-%04x-%04x-%04x%04x%04x',
// 32 bits for "time_low"
mt_rand(0, 0xffff), mt_rand(0, 0xffff),
// 16 bits for "time_mid"
mt_rand(0, 0xffff),
// 16 bits for "time_hi_and_version",
// four most significant bits holds version number 4
mt_rand(0, 0x0fff) | 0x4000,
// 16 bits, 8 bits for "clk_seq_hi_res",
// 8 bits for "clk_seq_low",
// two most significant bits holds zero and one for variant DCE1.1
mt_rand(0, 0x3fff) | 0x8000,
// 48 bits for "node"
mt_rand(0, 0xffff), mt_rand(0, 0xffff), mt_rand(0, 0xffff)
);
}
public static function v5($namespace, $name) {
if(!self::is_valid($namespace)) return false;
// Get hexadecimal components of namespace
$nhex = str_replace(array('-','{','}'), '', $namespace);
// Binary Value
$nstr = '';
// Convert Namespace UUID to bits
for($i = 0; $i < strlen($nhex); $i+=2) {
$nstr .= chr(hexdec($nhex[$i].$nhex[$i+1]));
}
// Calculate hash value
$hash = sha1($nstr . $name);
// Format and return UUID
return sprintf('%08s-%04s-%04x-%04x-%12s',
// 32 bits for "time_low"
substr($hash, 0, 8),
// 16 bits for "time_mid"
substr($hash, 8, 4),
// 16 bits for "time_hi_and_version",
// four most significant bits holds version number 5
(hexdec(substr($hash, 12, 4)) & 0x0fff) | 0x5000,
// 16 bits, 8 bits for "clk_seq_hi_res",
// 8 bits for "clk_seq_low",
// two most significant bits holds zero and one for variant DCE1.1
(hexdec(substr($hash, 16, 4)) & 0x3fff) | 0x8000,
// 48 bits for "node"
substr($hash, 20, 12)
);
}
public static function is_valid($uuid) {
return preg_match('/^\{?[0-9a-f]{8}\-?[0-9a-f]{4}\-?[0-9a-f]{4}\-?'.
'[0-9a-f]{4}\-?[0-9a-f]{12}\}?$/i', $uuid) === 1;
}
}
Do not use uniqid() in any context where security is involved. It is too predictable to be used in such context.
Upvotes: 6
Reputation: 12087
this will create a unique id for you which is at least 20 chars long
$id = '';
while(strlen($id) < 20)
{
$id .= uniqid();
}
Upvotes: 0
Reputation: 2027
Use uniqueid()
string uniqid ([ string $prefix = "" [, bool $more_entropy = false ]] )
Although if it's unique, I don't know why you have a minimum length requirement.
Upvotes: 1
Reputation: 17817
Try uniqid() http://php.net/manual/en/function.uniqid.php
If you can use pecl you can try this module: http://pecl.php.net/package/uuid
Theres also something if you use Ubuntu in your web server: http://code.google.com/p/php-uuid/
Upvotes: 5