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What iteration rules apply to crypt () using CRYPT_EXT_DES?

My test file is as follows:

echo crypt('string', '_....salt');//error echo crypt('string', '_A...salt');//fast echo crypt('string', '_AAAAsalt');//slow

Explanation specified at http://www.php.net/manual/en/function.crypt.php :

CRYPT_EXT_DES - an extended DES-based hash. "Salt" is a 9-character string consisting of an underscore followed by 4 bytes of iteration count and 4 bytes of salt. They are encoded as printable characters. First, 6 bits per character, the least significant character. Values ​​0 through 63 are encoded as "./0-9A-Za-z". Using invalid characters in the salt will cause crypt () to crash.

A dot is a printable character, so why does it return an error? And what "order" applies to the characters used, resulting in "AAAA" more iterations than "A ..."?

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This question is a bit outdated, however I found it trying to wrap my head around how to create a hash class for internal use here, and I came up with this little function that will base64 encode an integer with the corresponding characters / value, which should be used as an iteration count 4 character. Possible values: from 1 to 16 777 215

 private function base64_int_encode($num){ $alphabet_raw = "./0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"; $alphabet = str_split($alphabet_raw); $arr = array(); $base = sizeof($alphabet); while($num){ $rem = $num % $base; $num = (int)($num / $base); $arr[]=$alphabet[$rem]; } $arr = array_reverse($arr); $string = implode($arr); return str_pad($string, 4, '.', STR_PAD_LEFT); }

Hope this helps someone!

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It says everything in the cited paragraph: - the least significant character - Values ​​from 0 to 63 are encoded as "./0-9A-Za-z"

So, in your example, “_.... salt” will mean 0 rounds, which obviously can't work. and "_A ... salt" is less than "_AAAAsalt", given that the least significant character comes first.

"_... Asalt" will also be more than "_A ... salt"

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Klathmon code is good, but has some bugs:

The first is the alphabet

 It is: ./0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ Should be: ./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz

Second order of characters / numbers

 It generates for example: ...z But it should generate: z...

Improved code:

 function base64_int_encode($num) { $alphabet_raw='./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'; $alphabet=str_split($alphabet_raw); $arr=array(); $base=sizeof($alphabet); while($num) { $rem=$num % $base; $num=(int)($num / $base); $arr[]=$alphabet[$rem]; } $string=implode($arr); return str_pad($string, 4, '.', STR_PAD_RIGHT); }
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The number system used in extended DES:

 .... - 0 (Extended DES error) /... - 1 0... - 2 1... - 3 2... - 4 3... - 5 4... - 6 5... - 7 6... - 8 7... - 9 8... - 10 z... - 63 ./.. - 64 //.. - 65 0/.. - 66 1/.. - 67 Y/.. - 100 61.. - 200 g2.. - 300 E4.. - 400 o5.. - 500 M7.. - 600 w8.. - 700 UA.. - 800 2C.. - 900 cD.. - 1000 zz.. - 4095 ../. - 4096 /./. - 4097 0./. - 4098 1./. - 4099 xzzz - 16 777 213 yzzz - 16 777 214 zzzz - 16 777 215

And in connection with salt:

 _/...salt - 1 _0...salt - 2 _1...salt - 3 _2...salt - 4 _3...salt - 5 _4...salt - 6 _5...salt - 7 _6...salt - 8 _7...salt - 9 _8...salt - 10 _z...salt - 63 _./..salt - 64 _//..salt - 65 _0/..salt - 66 _1/..salt - 67 _Y/..salt - 100 _61..salt - 200 _g2..salt - 300 _E4..salt - 400 _o5..salt - 500 _M7..salt - 600 _w8..salt - 700 _UA..salt - 800 _2C..salt - 900 _cD..salt - 1000 _zz..salt - 4095 _../.salt - 4096 _/./.salt - 4097 _0./.salt - 4098 _1./.salt - 4099 _xzzzsalt - 16 777 213 _yzzzsalt - 16 777 214 _zzzzsalt - 16 777 215
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