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StringObfuscator.java

import java.util.Scanner;

import javax.xml.bind.annotation.adapters.HexBinaryAdapter;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;

public final class StringObfuscator {

    public static boolean matchesHash(String str, String hash) {
        return getHash(str).equals(hash);
    }

    public static String getHash(String str) {
        if(str != null)
            try {
                MessageDigest md = MessageDigest.getInstance("SHA-256");
                return new HexBinaryAdapter().marshal(md.digest(dontRainbowTableMeOrMySonEverAgain(str).getBytes()));
            } catch (NoSuchAlgorithmException e) {
                e.printStackTrace();
            }
        return "";
    }

    private static String dontRainbowTableMeOrMySonEverAgain(String str) {
        str += reverseString(str);
        SecureRandom rand = new SecureRandom(str.getBytes());
        int l = str.length();
        int steps = rand.nextInt(l);
        char[] chrs = str.toCharArray();
        for(int i = 0; i < steps; i++) {
            int indA = rand.nextInt(l);
            int indB;
            do {
                indB = rand.nextInt(l);
            } while(indB == indA);
            char c = (char) (chrs[indA] ^ chrs[indB]);
            chrs[indA] = c;
        }

        return String.copyValueOf(chrs);
    }

    private static String reverseString(String str) {
        char[] chars = new char[str.length()];
        for(int i = 0; i < chars.length; i++)
            chars[i] = str.charAt(str.length() - 1 - i);
        return String.copyValueOf(chars);
    }

    public static void main(String[] args) {
        Scanner br = new Scanner(System.in);
        String buf;
        try {
                while((buf = br.nextLine()) != null) {
                        System.out.println(buf + " " + getHash(buf));
                }
        } catch(Exception e) {}
    }
}