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HomeBackend DevelopmentPHP TutorialDetailed explanation of php Bcrypt password encryption mechanism

Detailed explanation of php Bcrypt password encryption mechanism

Jul 05, 2017 am 09:43 AM
bcryptphpDetailed explanation

这篇文章主要给大家介绍了关于PHP更安全的密码加密机制Bcrypt的相关资料,文中介绍的非常详细,对大家具有一定的参考学习价值,需要的朋友们下面来一起学习学习吧。

前言

我们常常为了避免在服务器受到攻击,数据库被拖库时,用户的明文密码不被泄露,一般会对密码进行单向不可逆加密——哈希。

常见的方式是:

哈希方式 加密密码
md5(‘123456') e10adc3949ba59abbe56e057f20f883e
md5(‘123456' . ($salt = ‘salt')) 207acd61a3c1bd506d7e9a4535359f8a
sha1(‘123456') 40位密文
hash(‘sha256', ‘123456') 64位密文
hash(‘sha512', ‘123456') 128位密文

密文越长,在相同机器上,进行撞库消耗的时间越长,相对越安全。

比较常见的哈希方式是 md5 + 盐,避免用户设置简单密码,被轻松破解。

password_hash

但是,现在要推荐的是 password_hash() 函数,可以轻松对密码实现加盐加密,而且几乎不能破解。

$password = '123456';
 
var_dump(password_hash($password, PASSWORD_DEFAULT));
var_dump(password_hash($password, PASSWORD_DEFAULT));

password_hash 生成的哈希长度是 PASSWORD_BCRYPT —— 60位,PASSWORD_DEFAULT —— 60位 ~ 255位。PASSWORD_DEFAULT 取值跟 php 版本有关系,会等于其他值,但不影响使用。

每一次 password_hash 运行结果都不一样,因此需要使用 password_verify 函数进行验证。

$password = '123456';
 
$hash = password_hash($password, PASSWORD_DEFAULT);
var_dump(password_verify($password, $hash));

password_hash 会把计算 hash 的所有参数都存储在 hash 结果中,可以使用 password_get_info 获取相关信息。

$password = '123456';
$hash = password_hash($password, PASSWORD_DEFAULT);
var_dump(password_get_info($hash));

输出

array(3) {
 ["algo"]=>
 int(1)
 ["algoName"]=>
 string(6) "bcrypt"
 ["options"]=>
 array(1) {
 ["cost"]=>
 int(10)
 }
}

注意:不包含 salt

可以看出我当前版本的 PHP 使用 PASSWORD_DEFAULT 实际是使用 PASSWORD_BCRYPT

password_hash($password, $algo, $options) 的第三个参数 $options 支持设置至少 22 位的 salt。但仍然强烈推荐使用 PHP 默认生成的 salt,不要主动设置 salt。

当要更新加密算法和加密选项时,可以通过 password_needs_rehash 判断是否需要重新加密,下面的代码是一段官方示例

$options = array('cost' => 11);
// Verify stored hash against plain-text password
if (password_verify($password, $hash))
{
 // Check if a newer hashing algorithm is available
 // or the cost has changed
 if (password_needs_rehash($hash, PASSWORD_DEFAULT, $options))
 {
  // If so, create a new hash, and replace the old one
  $newHash = password_hash($password, PASSWORD_DEFAULT, $options);
 }
 // Log user in
}

password_needs_rehash 可以理解为比较 $algo + $optionpassword_get_info($hash) 返回值。

password_hash 运算慢

password_hash 是出了名的运行慢,也就意味着在相同时间内,密码重试次数少,泄露风险降低。

$password = '123456';
var_dump(microtime(true));
var_dump(password_hash($password, PASSWORD_DEFAULT));
var_dump(microtime(true));
 
echo "\n";
 
var_dump(microtime(true));
var_dump(md5($password));
for ($i = 0; $i < 999; $i++)
{
 md5($password);
}
var_dump(microtime(true));

输出

float(1495594920.7034)
string(60) "$2y$10$9ZLvgzqmiZPEkYiIUchT6eUJqebekOAjFQO8/jW/Q6DMrmWNn0PDm"
float(1495594920.7818)

float(1495594920.7818)
string(32) "e10adc3949ba59abbe56e057f20f883e"
float(1495594920.7823)

password_hash 运行一次耗时 784 毫秒, md5 运行 1000 次耗时 5 毫秒。这是一个非常粗略的比较,跟运行机器有关,但也可以看出 password_hash 运行确实非常慢。

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