how to decrypt the crypt("name")

how开发者_如何学JAVA to decrypt the crypt("name")

---

You can't. From the documentation:

Note: There is no decrypt function, since crypt() uses a one-way algorithm.

Reading documentation helps ;)

---

crypt is one way hashing, you can't decrypt it.

If you want to compare it against another string you could crypt that too and then compare the two crypted strings.

---

crypt — One-way string hashing

---

use two way hashing

try with mcrypt

tutorial

---

Since crypt() produces a hash decrypting is not possible. If you need to guess the original data ("name") you can use a combination of a brute force algorithm and a huge dictionary.

---

I have find an example for mcrypt and create the two functions, for text or for binary files:

function MyDecrypt($input,$key){    
        /* Open module, and create IV */
        $td = mcrypt_module_open('des', '', 'ecb', '');
        $key = substr($key, 0, mcrypt_enc_get_key_size($td));
        $iv_size = mcrypt_enc_get_iv_size($td);
        $iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
        /* Initialize encryption handle */
        if (mcrypt_generic_init($td, $key, $iv) != -1) {
            /* 2 Reinitialize buffers for decryption */
            mcrypt_generic_init($td, $key, $iv);
            $p_t = mdecrypt_generic($td, $input);
                return $p_t;
            /* 3 Clean up */
            mcrypt_generic_deinit($td);
            mcrypt_module_close($td);
        }
} // end function Decrypt()


function MyCrypt($input, $key){
    /* Open module, and create IV */ 
    $td = mcrypt_module_open('des', '', 'ecb', '');
    $key = substr($key, 0, mcrypt_enc_get_key_size($td));
    $iv_size = mcrypt_enc_get_iv_size($td);
    $iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
    /* Initialize encryption handle */
    if (mcrypt_generic_init($td, $key, $iv) != -1) {
        /* 1 Encrypt data */
        $c_t = mcrypt_generic($td, $input);
        mcrypt_generic_deinit($td);
            return $c_t;
        /* 3 Clean up */
        mcrypt_generic_deinit($td);
        mcrypt_module_close($td);
    }
}

For Example Crypt a string :

    $original_text = "Hello world !";
    $password = "abc123";
echo '<p>Original_text: '.$original_text.'</p>';
    $crypted_text = MyCrypt($original_text,$password);
echo '<p>Crypted_text: '.$crypted_text.'</p>';
    $decrypted_text= MyDecrypt($crypted_text,$password);
echo '<p>Decrypted_text: '.$decrypted_text.'</p>';

echo '<p>And if I try with a wrong password?</p>';
    $wrong_decrypted_text= MyDecrypt($crypted_text,"wrong_pw");
echo '<p>Decrypted with wrong password: '.$wrong_decrypted_text.'</p>';

I hope helpful

---

You can't truly decrypt it, because there are (infinitely) many strings such that crypt($input) == crypt("name") -- but you can, via brute-force trial-and-error, find some of those strings.

If you know or suspect that the original string is a short dictionary word, and you find a short dictionary word that produces the same output, chances are you have "decrypted" the original string.

md5 and many weaker hash functions are attacked in this way routinely.

---

<?php

$hashed_password = crypt('mypassword'); // let the salt be automatically generated

/* You should pass the entire results of crypt() as the salt for comparing a
   password, to avoid problems when different hashing algorithms are used. (As
   it says above, standard DES-based password hashing uses a 2-character salt,
   but MD5-based hashing uses 12.) */
if (hash_equals($hashed_password, crypt($user_input, $hashed_password))) {
   echo "Password verified!";
}

?>