2014-01-01 03:11
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i want to use mcrypt to create a 256 bit token to set as the cookie for the user.

I have read a number of articles suggesting to use mcrypt DEV_RANDOM

I am using the code

$size = mcrypt_get_iv_size(MCRYPT_CAST_256, MCRYPT_MODE_CFB);
$iv = mcrypt_create_iv($size, MCRYPT_DEV_RANDOM);

But the result i get when i output the token is


Is this what it is supposed to look like? iF not, what do i have to do to generate a proper token.


图片转代码服务由CSDN问答提供 功能建议


我已阅读了许多建议使用mcrypt DEV_RANDOM的文章


  $  size = mcrypt_get_iv_size(MCRYPT_CAST_256,MCRYPT_MODE_CFB); 
 $ iv = mcrypt_create_iv($ size,MCRYPT_DEV_RANDOM); 



这是它应该是什么 看起来像? 我没有,我该怎么做才能生成一个合适的令牌。


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1条回答 默认 最新

  • dthjnc306679 2014-01-01 03:20

    Use bin2hex to get a more "friendly" representation of the data. bin2hex will convert the bytes you have generated into an ASCII encoded hex representation of the original string.

    $size = mcrypt_get_iv_size(MCRYPT_CAST_256, MCRYPT_MODE_CFB);
    $iv = mcrypt_create_iv($size, MCRYPT_DEV_RANDOM);
    $hexIv = bin2hex($iv);

    The reason you are getting the strange output is because you are taking a random sequence of bytes and trying to represent them at some kind of human readable text by treating it as a string encoded in whatever is the default encoding for the application you are viewing the string in (e.g you web browser).


    $size = mcrypt_get_iv_size(MCRYPT_CAST_256, MCRYPT_MODE_CFB);
    $iv = mcrypt_create_iv($size, MCRYPT_DEV_RANDOM);
    echo "RAW IV: ";
    echo $iv;
    echo "
     Hex: ";
    echo bin2hex($iv);


    RAW IV: ª£2æ|%ì­E½ßy²ý
    Hex: 0aaaa332e67c25ecad45bddf7919b2fd

    In addition you should note the following things:

    • MCRYPT_DEV_RANDOM will block if the entropy pool is depleted.
    • MCRYPT_DEV_URANDOM is most likely a better choice as it won't block. The output is less random, but this is fine for most purposes.
    • An alternative function is openssl_random_pseudo_bytes which, for your use-case, performs the same function as the two mcrypt_ function calls (with MCRYPT_DEV_URANDOM). It does not require the mcrypt extension, only that PHP was compiled with OpenSSL support.
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