PHP 使用非对称加密算法（RSA）

非对称加密算法需要两个密钥：公开密钥（publickey）和私有密钥（privatekey）。公开密钥与私有密钥是一对，如果用公开密钥对数据进行加密，只有用对应的私有密钥才能解密；如果用私有密钥对数据进行加密，那么只有用对应的公开密钥才能解密。
因为加密和解密使用的是两个不同的密钥，所以这种算法叫作非对称加密算法。

创建私钥、公钥

openssl genrsa -out rsa_private_key.pem 1024
//生成原始 RSA私钥文件
openssl pkcs8 -topk8 -inform PEM -in rsa_private_key.pem -outform PEM -nocrypt -out private_key.pem
//将原始 RSA私钥转换为 pkcs8格式
openssl rsa -in rsa_private_key.pem -pubout -out rsa_public_key.pem
//生成RSA公钥
//我们将私钥rsa_private_key.pem用在服务器端，公钥发放给android跟ios等前端。

服务端代码

class Rsa {    
    private static $PRIVATE_KEY = '-----BEGIN RSA PRIVATE KEY-----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-----END RSA PRIVATE KEY-----';    
    private static $PUBLIC_KEY = '-----BEGIN PUBLIC KEY-----MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCoZZ8iUBprOIc0kGckr5ax6/Fd9IKKMc/XHayKEAvqpS0oz0b1ojEkpkdZBk0OWNhp73YNV+YLKBwwxOwb3u3hl8nBLoG/RilEbBMdCf55cUzNsfn/XF5CiLr/aci/OHuTe6ULvXs280T5M+nUh3iKdiT6z9XrFbH69C+xFoNInwIDAQAB-----END PUBLIC KEY-----';   
 
    /**     
     * 获取私钥     
     * @return bool|resource     
     */    
    private static function getPrivateKey() 
    {        
        $privKey = self::$PRIVATE_KEY;        
        return openssl_pkey_get_private($privKey);    
    }    

    /**     
     * 获取公钥     
     * @return bool|resource     
     */    
    private static function getPublicKey()
    {        
        $publicKey = self::$PUBLIC_KEY;        
        return openssl_pkey_get_public($publicKey);    
    }    

    /**     
     * 私钥加密     
     * @param string $data     
     * @return null|string     
     */    
    public static function privEncrypt($data = '')    
    {        
        if (!is_string($data)) {            
            return null;       
        }        
        return openssl_private_encrypt($data,$encrypted,self::getPrivateKey()) ? base64_encode($encrypted) : null;    
    }    

    /**     
     * 公钥加密     
     * @param string $data     
     * @return null|string     
     */    
    public static function publicEncrypt($data = '')   
    {        
        if (!is_string($data)) {            
            return null;        
        }        
        return openssl_public_encrypt($data,$encrypted,self::getPublicKey()) ? base64_encode($encrypted) : null;    
    }    

    /**     
     * 私钥解密     
     * @param string $encrypted     
     * @return null     
     */    
    public static function privDecrypt($encrypted = '')    
    {        
        if (!is_string($encrypted)) {            
            return null;        
        }        
        return (openssl_private_decrypt(base64_decode($encrypted), $decrypted, self::getPrivateKey())) ? $decrypted : null;    
    }    

    /**     
     * 公钥解密     
     * @param string $encrypted     
     * @return null     
     */    
    public static function publicDecrypt($encrypted = '')    
    {        
        if (!is_string($encrypted)) {            
            return null;        
        }        
    return (openssl_public_decrypt(base64_decode($encrypted), $decrypted, self::getPublicKey())) ? $decrypted : null;    
    }
}

来源：简书