A simple java program to search password dumps for SHA-1 Hashed passwords from https://haveibeenpwned.com/passwords

PasswordFinder.java

import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;

/**
 * To run this you need the password dump of SHA-1 hashed passwords
 * 
 * Found at the bottom of this page https://haveibeenpwned.com/passwords
 * 
 * Set LOCATION_OF_PASSWORD_DUMP to the location of the EXTRACTED txt file
 * 
 * Set INPUT_PASSWORDS as your passwords to search for, or pass them as arguments on the command
 * line
 */
public class PasswordFinder {

    private static final String LOCATION_OF_PASSWORD_DUMP = "";

    private static final String[] INPUT_PASSWORDS = {"1234", "abcd"};

    public static void main(String[] args) {
        long start = System.nanoTime();
        if (args.length > 0) {
            new PasswordFinder().run(args);
        } else {
            new PasswordFinder().run(INPUT_PASSWORDS);
        }
        long end = System.nanoTime();
        System.out.println("Execution time: " + (end - start) / 1_000_000 + "ms");
    }

    private void run(String[] passwords) {
        var hashes = getHashes(passwords);
        System.out.println("Your hashed passwords: ");
        hashes.forEach(System.out::println);
        System.out.println();

        var foundHashes = findHashes(hashes);
        if (foundHashes.isEmpty()) {
            System.out.println("Your passwords were not found.");
        } else {
            System.out.println("Some passwords have been found!");
            for (String s : foundHashes) {
                int index = s.indexOf(":");
                System.out.println(s.substring(0, index) + " was found "
                        + s.substring(index + 1) + " times");
            }
        }
    }

    private List<String> findHashes(List<String> hashes) {
        System.out.println("Searching for hashed passwords, please wait ...");
        List<String> list = new ArrayList<>();
        try (Stream<String> stream = Files.lines(Paths.get(LOCATION_OF_PASSWORD_DUMP))) {
            list = stream.filter(e -> hashes.contains(e.substring(0, e.indexOf(":"))))
                    .collect(Collectors.toList());
        } catch (IOException e) {
            e.printStackTrace();
        }
        return list;
    }

    private List<String> getHashes(String[] passwords) {
        var list = new ArrayList<String>();
        MessageDigest md = null;
        try {
            md = MessageDigest.getInstance("SHA-1");
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        }

        for (String s : passwords) {
            byte[] hash = md.digest(s.getBytes(StandardCharsets.UTF_8));
            list.add(bytesToHex(hash));
        }
        return list;
    }

    private static String bytesToHex(byte[] hash) {
        StringBuilder hexString = new StringBuilder();
        for (int i = 0; i < hash.length; i++) {
            String hex = Integer.toHexString(0xff & hash[i]);
            if (hex.length() == 1) {
                hexString.append('0');
            }
            hexString.append(hex);
        }
        return hexString.toString().toUpperCase();
    }
}