PHP - Generate an 8 character hash from an integer

Question

Is there a way to take any number, from say, 1 to 40000 and generate an 8 character hash?

I was thinking of using base_convert but couldn't figure out a way to force it to be an 8 character hash.

Any help would be appreciated!

With `base_convert`, you could go down to a maximum of 3 characters (!) for your range of numbers. If you always need 8, you probably want [`(new Id())->encode($id)`](https://github.com/delight-im/PHP-IDs). You may have to prepend leading zeros (or other characters), but even substrings of MD5 can have leading zeros (though with lower probability). — caw, Nov 20 '19 at 15:10

score 23 · Accepted Answer · edited Mar 26 '10 at 02:24

23

Why don't you just run md5 and take the first 8 characters?

Because you are wanting a hash, it doesn't matter whether portions are discarded, but rather that the same input will produce the same hash.

$hash = substr(md5($num), 0, 8);

edited Mar 26 '10 at 02:24

nickf

520,029
197
633
717

answered Mar 26 '10 at 02:22

Nathan Osman

67,908
69
250
347

3

Thanks to whoever fixed that. I must be asleep. – Nathan Osman Mar 26 '10 at 02:25
3

Is there any chance of a collision in my number range? – doc Mar 26 '10 at 02:31
Better instinct tells me no... but you might want to run a test. Since 40,000 is not a huge number, you could easily test that. – Nathan Osman Mar 26 '10 at 02:44
1

Thanks, I'm testing this now with a random hash associated with a session. – doc Mar 26 '10 at 02:46

score 4 · Answer 2 · answered Mar 26 '10 at 02:27

4

>>> math.exp(math.log(40000)/8)
3.7606030930863934

Therefore you need 4 digit-symbols to produce a 8-character hash from 40000:

sprintf("%08s", base_convert($n, 10, 4))

answered Mar 26 '10 at 02:27

Ignacio Vazquez-Abrams

740,318
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1,296
1,325

score 1 · Answer 3 · answered Jun 12 '12 at 12:29

1

For php:

$seed = 'JvKnrQWPsThuJteNQAuH';
$hash = sha1(uniqid($seed . mt_rand(), true));

# To get a shorter version of the hash, just use substr
$hash = substr($hash, 0, 10);

http://snipplr.com/view.php?codeview&id=20236

answered Jun 12 '12 at 12:29

Ariel

11
1

score 0 · Answer 4 · answered Mar 26 '10 at 02:23

0

there are many ways ...

one example

$x = ?
$s = '';
for ($i=0;$i<8;++$i)
{
    $s .= chr( $x%26 + ord('a') );
    $x /= 26;
}

answered Mar 26 '10 at 02:23

SteelBytes

6,806
1
25
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isn't this just effectively changing the base of the number? – nickf Mar 26 '10 at 02:25
sure. but the request was pretty vague - it just asked for an 8char hash. – SteelBytes Mar 26 '10 at 02:26
Sorry about how vaguely I asked the question :( I'm trying to generate an 8 character hash from any integer but don't just want to pad the remaining length of the hash with something. Any ideas? – doc Mar 26 '10 at 02:34

score 0 · Answer 5 · answered Mar 26 '10 at 02:26

0

$hash = substr(hash("sha256",$num), 0, 8);

answered Mar 26 '10 at 02:26

ghostdog74

307,646
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250
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How does this differ from mine? `md5` is pretty strong. Why `sha256`? – Nathan Osman Mar 26 '10 at 02:28
@GeorgeEdison: md5 is pretty weak. It just takes hours to create collisions. – neo Mar 26 '10 at 16:02
Hey, this can clear u which one is best [link](https://stackoverflow.com/questions/2948156/algorithm-complexity-security-md5-or-sha1) – Anurag pareek Mar 14 '18 at 06:49

score 0 · Answer 6 · answered Mar 26 '10 at 12:47

So you want to convert a 6 digit number into a 8 digit string reproducibly?

sprintf("%08d", $number);

Certainly a hash is not reversible - but without a salt / IV it might be a bit easy to hack. A better solution might be:

substr(sha1($number . $some_secret),0,8);

C.

PHP - Generate an 8 character hash from an integer

6 Answers6

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