Generating a 10 digit random confirmation string php

Question

I am trying to create a 'confirmation code' for every user account created on my website and storing it in the db along with their personal information. As you can see in the example below, I tried to generate a random string factoring in the time variable, however, the string is unneccessarily long.

I would like the string to be shorter than the one produced by md5 I was wondering if there is a relatively easy way to generate 10 digit (max) alphanumeric string that has an extremely low collision rate?

What I tried:

  md5(mt_rand(10000,99999).time() . 'example@domain.com');

Output:

0dd6854dba19e70cfda0ab91595e0376

Why are you concerned with the length of the string? What's wrong with a longer string? — tkone, Jul 02 '12 at 20:05
If a user needs help with their account and I ask for their confirmation number, it would be easier to not have a 30+ character string, especially if they got 1 character wrong... — AnchovyLegend, Jul 02 '12 at 20:06
@MHZ: I guess you could just use your existing MD5 string, and take the first 10 chars? — houbysoft, Jul 02 '12 at 20:07
@houbysoft I thought about that:) Not sure if that is the best solution though... — AnchovyLegend, Jul 02 '12 at 20:09
@MHZ: see my answer for another solution, using `openssl_random_pseudo_bytes`. — houbysoft, Jul 02 '12 at 20:15
I'd take the first 10 chars of `md5()`. Good hash functions such as this ripple even a small change in input throughout the whole of its output, so your collision rate is effectively 1/2^40; that's pretty good. — halfer, Jul 02 '12 at 20:32

houbysoft · Accepted Answer · 2012-07-02T20:21:16.097

5

PHP provides the openssl_random_pseudo_bytes function that can be made to securely do what you want.

Do something like:

bin2hex(openssl_random_pseudo_bytes(5))

The above will give you something like e9d196aa14, for example.

Alternatively, just take the first 10 chars of your existing MD5 string.

edited Jul 02 '12 at 20:21

answered Jul 02 '12 at 20:14

houbysoft

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This method is pretty nice. Thanks for the help! I am trying to decide if I should go with the first 10 characters of the long string generated in my initial post, or this method... – AnchovyLegend Jul 02 '12 at 20:20
1

@MHZ This is technically probably the most correct answer, but might be overkill for non-cryptographic use. Since you aren't basing security on the hash code, taking the first ten characters of MD5 is probably fine. – Jazz Jul 02 '12 at 20:22
1

Overkill in what sense? It creates a relatively short random string with negligibly low collision rates, right? Wouldn't I be better off with this method? Considering it accomplishes the task with less code:) – AnchovyLegend Jul 02 '12 at 20:27

score 1 · Answer 2 · answered Jul 02 '12 at 20:07

1

http://php.net/manual/en/function.uniqid.php

+

http://br.php.net/manual/en/function.substr.php

answered Jul 02 '12 at 20:07

Rodolfo Bandeira

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score 0 · Answer 3 · answered Sep 22 '12 at 02:42

This will generate you any random output string from Aa-Zz and 0-9 characters.

function genString($length) {
    $lowercase = "qwertyuiopasdfghjklzxcvbnm";
    $uppercase = "ASDFGHJKLZXCVBNMQWERTYUIOP";
    $numbers = "1234567890";
    $specialcharacters = "{}[];:,./<>?_+~!@#";
    $randomCode = "";
    mt_srand(crc32(microtime()));
    $max = strlen($lowercase) - 1;
    for ($x = 0; $x < abs($length/3); $x++) {
        $randomCode .= $lowercase{mt_rand(0, $max)};
    }
    $max = strlen($uppercase) - 1;
    for ($x = 0; $x < abs($length/3); $x++) {
        $randomCode .= $uppercase{mt_rand(0, $max)};
    }
    $max = strlen($specialcharacters) - 1;
    for ($x = 0; $x < abs($length/3); $x++) {
        $randomCode .= $specialcharacters{mt_rand(0, $max)};
    }
    $max = strlen($numbers) - 1;
    for ($x = 0; $x < abs($length/3); $x++) {
        $randomCode .= $numbers{mt_rand(0, $max)};
    }
    return str_shuffle($randomCode);
}

Usage

$str = genString(10);

score 0 · Answer 4 · answered Jul 22 '14 at 13:59

0

I think the best way is

$random = substr(number_format(time() * rand(),0,'',''),0,10); // you can increase the digits by changing 10 to desired digit

Please check it out

answered Jul 22 '14 at 13:59

Suneel Kumar

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score -1 · Answer 5 · answered Jul 02 '12 at 20:09

-1

Try using http://php.net/manual/en/function.str-split.php

answered Jul 02 '12 at 20:09

Andrey

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How is this relvant or useful? :) – AnchovyLegend Jul 02 '12 at 20:21
You could do something similar to `$short = str_split($long,10);` then get the first value in array $short. Of course, you could use somebody else's suggestion. :) – Andrey Jul 02 '12 at 20:38

Generating a 10 digit random confirmation string php

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