Shorter hash strings without compromising security [duplicate]

This question already has answers here: Closed 11 years ago.

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php short hash

MD5 hashes are long and inconvenient to use. How can I further encode a md5 string to produce a shorter string using a subset of characters, for example a-z, A-Z and 0-9? jsfiddle.net is doing som开发者_如何学编程ething like this on their website to produce short links easy to copy and paste and look like this: http://jsfiddle.net/uY7Pk/

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1. Generate a random N-character string.
2. See if anything else already has that string as its shorturl in the database.
3. If yes, go to 1. If no, store that string as the shorturl for the resource in the database.

There's no need to use hashing for url shorteners when you have a persistent datastore, because you're not actually encoding the long url, you're just associating a token with it.

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JSFiddle is using an algorithm to shorten the URL, that has not much to do with MD5 hashing.

Since hash algorithms usually generate a certain length of Hex Data...

echo md5("Hello World");    
-> b10a8db164e0754105b7a99be72e3fe5

...there might be algorithms to compress those hashes slightly further, but they will certainly result in a binary blob - which ain't a specific subset of characters, for example a-z, A-Z and 0-9.

Sidenote: PHPass is currently a solid way to use hashes in php.

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I think you're getting confused between encryption and URL-shortening.

What you see on JSfiddle isn't encryption, it's a unique id that refers to the page. Instead of using solely numerical IDs, they're using letters too which allows many more combinations from the same number of characters.

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use base64_encode($hash). It will produce an encode version which usualy is shorter.

Another way is to compute a crc32 which is a 32bit integer

But it depends on whether you need to recover your have afterwards.