How to generate possible password combinations fro

Question

I am trying to generate a list of strings (possible passwords) that I can then hash (SHA-256) to compare to an already existing password hashes that I have.

I know that the password must be a popular boys or girls name, with no specified case, followed by a number ranging from 0 to 9999, e.g BoB167, AliCE1000, conNor99, tHe9329

How can I go about generating the possible password strings that the password can be so that I can then hash them to compare with my hashes

Does anyone know where I can start I was thinking to just create a method that takes in all possible characters add every combination to a string but im unsure as to how to do this

Answer 1

Your question is a little bit too broad, but since you indicated in the comments that your issue is coming up with the lowercase/uppercase combinations of the names, I'll just address that part in my answer.

• For a given name with n characters, there are 2ⁿ possible combinations of upper and lowercase letters.
  E.g. for bob there are 2³ = 8 possible combinations.

• Looping from 0 to 2ⁿ will yield 2ⁿ consecutive integers.
  E.g. for bob, that would be 0, 1, 2, 3, 4, 5, 6 and 7.

• The bit patterns of those integers can be used to determine whether a character needs to be uppercase or lowercase.
  E.g. for bob, the bit patterns would be 000, 001, 010, 011, and so on.
• You can then use a little bit of bit shifting magic (borrowed from here) to determine whether the n^th bit in an integer is set to generate the actual name combinations.

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Example code

public class Test {
    public static void main(String[] args) {
        combinations("bob");
    }

    private static void combinations(String name) {
        char[] chars  = name.toCharArray();

        for (int i = 0; i < Math.pow(2, chars.length); i++) {
            char[] result = new char[chars.length];

            for (int n = 0; n < chars.length; n++) {
                result[n] = isBitSet(i, n) ? Character.toUpperCase(chars[n])
                                           : Character.toLowerCase(chars[n]);
            }

            System.out.println(result);
        }
    }

    private static boolean isBitSet(int i, int n) {
        return ((i & (1 << n)) != 0);
    }
}

Output

This yields the following output:

bob
Bob
bOb
BOb
boB
BoB
bOB
BOB