对称加密

相关资料

https://en.wikipedia.org/wiki/Symmetric-key_algorithm
https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation

# man enc

对称加密：symmetric-key encryption

Symmetric-key algorithms are algorithms for cryptography that use the same cryptographic keys for both encryption of plaintext and decryption of ciphertext.

Symmetric-key encryption can use either stream ciphers or block ciphers.

常用对称加密算法

DES、AES

加密模式

Electronic Codebook(ECB) 电子密码本

The simplest of the encryption modes is the Electronic Codebook (ECB) mode.
The message is divided into blocks, and each block is encrypted separately.

Cipher Block Chaining(CBC) 密码分组链接

In CBC mode, each block of plaintext is XORed with the previous ciphertext block before being encrypted.
To make each message unique, an initialization vector must be used in the first block.

CBC has been the most commonly used mode of operation. Its main drawbacks are that encryption is sequential (i.e., it cannot be parallelized), and that the message must be padded to a multiple of the cipher block size.

openssl

# openssl des3 -salt -in file.txt -out file.des3
# openssl des3 -d -salt -in file.des3 -out file.txt

# openssl aes-256-cbc -in file.txt -out file.aes

PHP

# openssl_get_cipher_methods
# openssl_encrypt
# openssl_decrypt

密钥生成

你所使用的密钥应该越随机越好，它不能是一个普通的文本字符串，经过哈希函数处理过也不行。
为了生成一个合适的密钥，你应该使用下面提供的 create_key() 方法：

// $key will be assigned a 16-byte (128-bit) random key
$key = create_key(16);
$key = hex2bin($key);

function create_key($length)
{
    if (function_exists('random_bytes'))
    {
        try
    {
        return random_bytes((int) $length);
    }
    catch (Exception $e)
    {
        log_message('error', $e->getMessage());
        return FALSE;
    }
    }

    $is_secure = NULL;
    $key = openssl_random_pseudo_bytes($length, $is_secure);
    return ($is_secure === TRUE) ? $key : FALSE;
}

加密解密

$data = 'hello,world!';
$method = 'aes-128-cbc';
$key = create_key(16);
$iv = ($iv_size = openssl_cipher_iv_length($method)) ? create_key($iv_size) : '';
$cipherText = openssl_encrypt($data,$method,$key,1,$iv);
$plainText = openssl_decrypt($cipherText,$method,$key,1,$iv);
echo base64_encode($cipherText);echo "<br />";echo $plainText;