Question

When comparing passwords, there is always an issue of keeping them in memory. Instead, the moment a password is introduced, i’d like to replace it with its md5 snapshot (or any other hash producing function)

Assuming you have a Key Value pair String password = "Secret";, what is the simplest way to scramble “secret” to something unique?

Answer 1

Use a MessageDigest. Something like this:

MessageDigest algorithm = MessageDigest.getInstance("MD5");
algorithm.reset();
algorithm.update(password.getBytes());
byte bytes[] = algorithm.digest();
StringBuffer sb = new StringBuffer();
for (byte b : bytes) {
    String hex = Integer.toHexString(0xff & b);
    if(hex.length() == 1)
        sb.append('0');
    sb.append(hex);
}
result = sb.toString();

Also, watch out of the NoSuchAlgorithmException that can be thrown by the getInstance method if the MD5 algorithm is somehow not available.