What's the best way to create a short hash, similar to what tiny Url does?

Question

I\'m currently using MD5 hashes but I would like to find something that will create a shorter hash that uses just [a-z][A-Z][0-9]. It only needs to be around 5-

Answer 1

Is your goal to create a URL shortener or to create a hash function?

If your goal is to create a URL shortener, then you don't need a hash function. In that case, you just want to pre generate a sequence of cryptographically secure random numbers, and then assign each url to be encoded a unique number from the sequence.

You can do this using code like:

using System.Security.Cryptography;

const int numberOfNumbersNeeded = 100;
const int numberOfBytesNeeded = 8;
var randomGen = RandomNumberGenerator.Create();
for (int i = 0; i < numberOfNumbersNeeded; ++i)
{
     var bytes = new Byte[numberOfBytesNeeded];
     randomGen.GetBytes(bytes);
}

Using the cryptographic number generator will make it very difficult for people to predict the strings you generate, which I assume is important to you.

You can then convert the 8 byte random number into a string using the chars in your alphabet. This is basically a change of base calculation (from base 256 to base 62).