这篇文章主要介绍了使用openssl实现rsa非对称加密算法的示例，大家参考使用吧

<?php
/**
 * 使用openssl实现非对称加密
 * @since 2010-07-08
 */
class Rsa
{
    /**
     * private key
     */
        private $_privKey;

        /**
         * public key
         */
        private $_pubKey;

        /**
         * the keys saving path
         */
        private $_keyPath;

        /**
         * the construtor,the param $path is the keys saving path
         */
        public function __construct($path)
        {
                if(empty($path) || !is_dir($path)){
                        throw new Exception('Must set the keys save path');
                }

                $this->_keyPath = $path;
        }

        /**
         * create the key pair,save the key to $this->_keyPath
         */
        public function createKey()
        {
                $r = openssl_pkey_new();
                openssl_pkey_export($r, $privKey);
                file_put_contents($this->_keyPath . DIRECTORY_SEPARATOR . 'priv.key', $privKey);
                $this->_privKey = openssl_pkey_get_public($privKey);

                $rp = openssl_pkey_get_details($r);
                $pubKey = $rp['key'];
                file_put_contents($this->_keyPath . DIRECTORY_SEPARATOR .  'pub.key', $pubKey);
                $this->_pubKey = openssl_pkey_get_public($pubKey);
        }

        /**
         * setup the private key
         */
        public function setupPrivKey()
        {
                if(is_resource($this->_privKey)){
                        return true;
                }
                $file = $this->_keyPath . DIRECTORY_SEPARATOR . 'priv.key';
                $prk = file_get_contents($file);
                $this->_privKey = openssl_pkey_get_private($prk);
                return true;
        }

        /**
         * setup the public key
         */
        public function setupPubKey()
        {
                if(is_resource($this->_pubKey)){
                        return true;
                }
                $file = $this->_keyPath . DIRECTORY_SEPARATOR .  'pub.key';
                $puk = file_get_contents($file);
                $this->_pubKey = openssl_pkey_get_public($puk);
                return true;
        }

        /**
         * encrypt with the private key
         */
        public function privEncrypt($data)
        {
                if(!is_string($data)){
                        return null;
                }

                $this->setupPrivKey();

                $r = openssl_private_encrypt($data, $encrypted, $this->_privKey);
                if($r){
                        return base64_encode($encrypted);
                }
                return null;
        }

        /**
         * decrypt with the private key
         */
        public function privDecrypt($encrypted)
        {
                if(!is_string($encrypted)){
                        return null;
                }

                $this->setupPrivKey();

                $encrypted = base64_decode($encrypted);

                $r = openssl_private_decrypt($encrypted, $decrypted, $this->_privKey);
                if($r){
                        return $decrypted;
                }
                return null;
        }

        /**
         * encrypt with public key
         */
        public function pubEncrypt($data)
        {
                if(!is_string($data)){
                        return null;
                }

                $this->setupPubKey();

                $r = openssl_public_encrypt($data, $encrypted, $this->_pubKey);
                if($r){
                        return base64_encode($encrypted);
                }
                return null;
        }

        /**
         * decrypt with the public key
         */
        public function pubDecrypt($crypted)
        {
                if(!is_string($crypted)){
                        return null;
                }

                $this->setupPubKey();

                $crypted = base64_decode($crypted);

                $r = openssl_public_decrypt($crypted, $decrypted, $this->_pubKey);
                if($r){
                        return $decrypted;
                }
                return null;
        }

        public function __destruct()
        {
                @ fclose($this->_privKey);
                @ fclose($this->_pubKey);
        }

}

//以下是一个简单的测试demo，如果不需要请删除
$rsa = new Rsa('ssl-key');

//私钥加密，公钥解密
echo 'source：我是老鳖<br />';
$pre = $rsa->privEncrypt('我是老鳖');
echo 'private encrypted:<br />' . $pre . '<br />';

$pud = $rsa->pubDecrypt($pre);
echo 'public decrypted:' . $pud . '<br />';

//公钥加密，私钥解密
echo 'source:干IT的<br />';
$pue = $rsa->pubEncrypt('干IT的');
echo 'public encrypt:<br />' . $pue . '<br />';

$prd = $rsa->privDecrypt($pue);
echo 'private decrypt:' . $prd;
?>

需要注意的是apache要支持OpenSSL