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algorithmrandomlicense-keyserial-number

Creating a large number of random serial keys

I am developing a application where user is only authenticated if he enters a serial key correctly. This serial key is matched with the serial key already present in database. This serial key should consists of 6 digit and 3 alphabets. Users get these key in written form from me.

How do I generate a large number (100,000,000 approx) of serial keys?

Solution

  • Simplest way in my opinion is:

    1. find a desired number in range [1,10000000), let it be x and it will represent your 6 digits.
    2. Find 3 characters (let's assume in range a-z). Let them be a,b,c.
    3. Your number is (a-'a' + b-'a'*26 + c-'a'*26*26)*10000000 + x

    (Where 'a' is the ascii representation of the character 'a', and a-'a' means the numeric ascii subtraction)

    Note that the generated number can even fit in a long - assuming it is 64 bits.

    Generation of several numbers can be simply done with iteration, start with a=b=c='a', and x=0, and start advancing (increase by 1). Once you reached x=10000000, increase a, if a passed z - increase b, .... (similar to what you would do in normal integer addition arithmetic).