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Bug #52989 the mcrypt_encrypt and mcrypt_decrypt functions are not accurate working.
Submitted: 2010-10-05 06:24 UTC Modified: 2010-10-13 12:44 UTC
From: info at wtovn dot com Assigned:
Status: Not a bug Package: *Encryption and hash functions
PHP Version: 5.3SVN-2010-10-05 (snap) OS: WIN32
Private report: No CVE-ID: None
 [2010-10-05 06:24 UTC] info at wtovn dot com
the mcrypt_encrypt and mcrypt_decrypt functions are not accurate working. 
please see script below.

Test script:
    $data = "Cộng hòa xã hội chủ nghĩa việt nam, độc lập tự do hạnh phúc";   
    $iv_size = mcrypt_get_iv_size(MCRYPT_3DES, MCRYPT_MODE_ECB);   
    $iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);   
    $key = "01";
    $crypttext = mcrypt_encrypt(MCRYPT_3DES, $key, $data, MCRYPT_MODE_ECB, $iv);   
    $key = "10";   
    $decrypt = mcrypt_decrypt (MCRYPT_3DES, $key , $crypttext , MCRYPT_MODE_ECB, $iv) ;  

then result are :

    $data = $decrypt ????


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 [2010-10-13 04:01 UTC] uramihsayibok at gmail dot com
Not a bug. It's due to the nature of DES.

The least significant bit of each byte in the key is NOT USED, and the only difference between the characters '0' and '1' is that least significant bit. You can see the same behavior swapping 'B' and 'C', 'P' and 'Q', and 'x' and 'y' (to give some examples). Generically, any even-numbered ASCII character can be swapped with its n+1 neighbor, and vice versa.

Separately: ECB mode does not use IVs so $iv is pointless.
 [2010-10-13 12:44 UTC]
-Status: Open +Status: Bogus
 [2010-10-13 12:44 UTC]
Thank you for taking the time to write to us, but this is not
a bug. Please double-check the documentation available at and the instructions on how to report
a bug at

Thanks for the explanation uramihsayibok; I did not know this.
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