正确使用方法 php openssl_encrypt

Question

我正在一个项目中使用密码学，我需要一些关于如何使用 openssl_encrypt 和 openssl_decrypt 的帮助，我只想知道最基本和正确的方法它。这是我到目前为止得到的：

// To encrypt a string

$dataToEncrypt = 'Hello World';

$cypherMethod = 'AES-256-CBC';
$key = random_bytes(32);
$iv = openssl_random_pseudo_bytes(openssl_cipher_iv_length($cypherMethod));

$encryptedData = openssl_encrypt($dataToEncrypt, $cypherMethod, $key, $options=0, $iv);

然后我存储 $cypherMethod、$key 和 $iv，以便在解密 $encryptedData 时使用。 （我们不详细说明我是如何存储这些值的，谢谢！）

// To decrypt an encrypted string

$decryptedData = openssl_decrypt($encryptedData, $cypherMethod, $key, $options=0, $iv);

首先，上面的示例代码是如何使用 php openssl_encrypt 的正确示例吗？

其次，我生成 $key 和 $iv 的方法是否正确且安全？因为我一直在阅读，所以密钥应该是加密安全的。

最后，AES-256-CBC 不需要 32-byte 值吗？如果是，那为什么openssl_cipher_iv_length() returns 的长度只有int(16)？不应该是int(32)吗？

Answer 1

First off, is the above example code a correct example of how to use php openssl_encrypt?

您对该函数的使用看起来是正确的，但是您可能需要考虑 CBC 以外的操作模式。 CBC 很难正确处理，因为仅在这种模式下加密数据就会遭到已知的攻击，例如臭名昭著的 CBC bit-flipping attack, which allows an attacker to make meaningful changes to the plaintext by modifying the ciphertext. If possible I would use an authenticated encryption mode like GCM if you can (looks like it's supported in PHP 7.1+ (Example #1)).

如果您使用 CBC 模式，请查看 Example #2 in the docs。请注意，在加密后，MAC（消息验证码）将在密文上计算并存储。这个MAC在解密密文之前需要重新计算，如果与存储的MAC不匹配则密文被修改，无效

Second, is my method to generate the $key and $iv correct and secure? Because I keep on reading, keys should be cryptographically secure.

需要使用加密安全随机数生成器生成密钥。幸运的是，大多数操作系统通过 /dev/urandom 提供了一个开箱即用的功能。 does a good job explaining how to read from /dev/urandom in PHP. openssl_random_pseudo_bytes should also be cryptographically secure but there are times when this is not the case.

初始化向量 (IV) 必须是随机的，绝不能与相同的密钥重复使用。

Lastly, isn't a 32-byte value required for AES-256-CBC? If yes, then why is it that openssl_cipher_iv_length() returns only int(16) as the length? Shouldn't it be int(32)?

AES 是一种适用于 128 位（16 字节）块的块密码，与密钥大小无关。

Answer 2

下面是openssl_encrypt和openssl_decrypt最基本的使用方法。确保创建 32 字节 secret_key 和 16 字节 secret_iv

function encrypt_decrypt($action, $string) 
    {
        $output = false;
        $encrypt_method = "AES-256-CBC";
        $secret_key = 'xxxxxxxxxxxxxxxxxxxxxxxx';
        $secret_iv = 'xxxxxxxxxxxxxxxxxxxxxxxxx';
        // hash
        $key = hash('sha256', $secret_key);    
        // iv - encrypt method AES-256-CBC expects 16 bytes 
        $iv = substr(hash('sha256', $secret_iv), 0, 16);
        if ( $action == 'encrypt' ) {
            $output = openssl_encrypt($string, $encrypt_method, $key, 0, $iv);
            $output = base64_encode($output);
        } else if( $action == 'decrypt' ) {
            $output = openssl_decrypt(base64_decode($string), $encrypt_method, $key, 0, $iv);
        }
        return $output;
    }

Answer 3

// --- Encrypt --- //
$key = openssl_digest("passkey", 'SHA256', TRUE);
$plaintext = "Data to be encrypted";
$ivlen = openssl_cipher_iv_length($cipher="AES-128-CBC");
$iv = openssl_random_pseudo_bytes($ivlen);
// binary cipher
$ciphertext_raw = openssl_encrypt($plaintext, $cipher, $key, OPENSSL_RAW_DATA, $iv);
// or replace OPENSSL_RAW_DATA & $iv with 0 & bin2hex($iv) for hex cipher (eg. for transmission over internet)

// or increase security with hashed cipher; (hex or base64 printable eg. for transmission over internet)
$hmac = hash_hmac('sha256', $ciphertext_raw, $key, true);
$ciphertext = base64_encode( $iv.$hmac.$ciphertext_raw );

// --- Decrypt --- //
$c = base64_decode($ciphertext);
$ivlen = openssl_cipher_iv_length($cipher="AES-128-CBC");
$iv = substr($c, 0, $ivlen);
$hmac = substr($c, $ivlen, $sha2len=32);
$ciphertext_raw = substr($c, $ivlen+$sha2len);
$original_plaintext = openssl_decrypt($ciphertext_raw, $cipher, $key, OPENSSL_RAW_DATA, $iv);
$calcmac = hash_hmac('sha256', $ciphertext_raw, $key, true);
if (hash_equals($hmac, $calcmac))
    echo $original_plaintext."\n";

Answer 4

   // --- Encrypt --- //
function encrypt($plaintext, $secret_key = "5fgf5HJ5g27", $cipher = "AES-128-CBC")
{

    $key = openssl_digest($secret_key, 'SHA256', TRUE);

    $ivlen = openssl_cipher_iv_length($cipher);
    $iv = openssl_random_pseudo_bytes($ivlen);
    // binary cipher
    $ciphertext_raw = openssl_encrypt($plaintext, $cipher, $key, OPENSSL_RAW_DATA, $iv);
    // or replace OPENSSL_RAW_DATA & $iv with 0 & bin2hex($iv) for hex cipher (eg. for transmission over internet)

    // or increase security with hashed cipher; (hex or base64 printable eg. for transmission over internet)
    $hmac = hash_hmac('sha256', $ciphertext_raw, $key, true);
    return base64_encode($iv . $hmac . $ciphertext_raw);
}


// --- Decrypt --- //
function decrypt($ciphertext, $secret_key = "5fgf5HJ5g27", $cipher = "AES-128-CBC")
{

    $c = base64_decode($ciphertext);

    $key = openssl_digest($secret_key, 'SHA256', TRUE);

    $ivlen = openssl_cipher_iv_length($cipher);

    $iv = substr($c, 0, $ivlen);
    $hmac = substr($c, $ivlen, $sha2len = 32);
    $ciphertext_raw = substr($c, $ivlen + $sha2len);
    $original_plaintext = openssl_decrypt($ciphertext_raw, $cipher, $key, OPENSSL_RAW_DATA, $iv);

    $calcmac = hash_hmac('sha256', $ciphertext_raw, $key, true);
    if (hash_equals($hmac, $calcmac))
        return $original_plaintext . "\n";
}

正确使用方法 php openssl_encrypt

Correct way to use php openssl_encrypt

php

encryption

cryptography

aes

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