Cannot decode some passwords?

Question

I added a password checker for my program, I thought it works fine since I could save the password in a file (encoded) and could enter the password in the password field and it let me into the main program without problems. However, today I was testing more and I found out that some passwords do not work and I have no idea why that is the case. I included both my methods, one does encode the password, the other one does decode it. The verify method I included is the one that reads from the password file, decodes the password and checks if the entered password equals the saved one. I couldnt find out what types of passwords do not work, its not the length, more like the characters which were used. Thanks in advance

public static char[] encode(int offset, char[] charArray) {

    char[] arrEnc = new char[charArray.length];

    for (int i = 0; i < charArray.length; i++) {

        int verschiebung = (charArray[i] + offset) % 128;

        arrEnc[i] = (char) (verschiebung);

    }
    return arrEnc;

}

public static char[] decode(int offset, char[] charArray) {

    char[] arrEnc = new char[charArray.length];

    int verschiebung;

    for (int i = 0; i < charArray.length; i++) {

        if (charArray[i] - offset < 0) {
            verschiebung = charArray[i] - offset + 128;

        } else {
            verschiebung = (charArray[i] - offset) % 128;

            arrEnc[i] = (char) (verschiebung);
        }
    }
    return arrEnc;

}

private void verify() {
    try {
        FileReader fr = new FileReader(pws);
        BufferedReader br = new BufferedReader(fr);
        char[] arr = br.readLine().toCharArray();
        char[] newArr = decode(arr.length, arr);
        String pw = new String(newArr);
        String masterPw = "Kassa";
        if (passwordField.getText().equals(pw) || 
                  passwordField.getText().equals(masterPw)) {
            setVisible(false);
            starto.setVisible(true);
            br.close();
        }

    } catch (Exception e) {
        e.printStackTrace();
    }
}

Any password should be able to be saved and decoded

Do you have specific examples of what does vs. does not work? — Not a JD, Mar 28 '19 at 17:36
yes, i just tested it with "testtesttest" and it does not work — DJ NoReality TXC_TryhardOne, Mar 28 '19 at 17:49
Please check: "System.out.println(decode(0, encode(0, "testtesttest".toCharArray())));" - yields testtesttest for me. — Not a JD, Mar 28 '19 at 17:51
I just tested changing the verify method, instead of reading the password in the file and decoding it, I encode the entered password and compare it with the saved password, then I printed them in the console and both were equal, however `if (testArr.equals(arr) || passwordField.getText().equals(masterPw)) { setVisible(false); starto.setVisible(true); }` does not do anything — DJ NoReality TXC_TryhardOne, Mar 28 '19 at 17:53
yes correct, what you said is the case, but apparently the if instruction doesnt set the other window to visible — DJ NoReality TXC_TryhardOne, Mar 28 '19 at 17:54
I just tested `Arrays.equals(encPw, arr)` and apparently that seems to work, at least for "testtesttest" — DJ NoReality TXC_TryhardOne, Mar 28 '19 at 18:06
Yep! works, so apparently the normal .equals methode does not work out for arrays, thanks for your help anyway! :D — DJ NoReality TXC_TryhardOne, Mar 28 '19 at 18:08
Yup, see https://stackoverflow.com/questions/8777257/equals-vs-arrays-equals-in-java — Not a JD, Mar 28 '19 at 18:15

score 0 · Answer 1 · answered Mar 28 '19 at 19:10

0

You have a mistake in the code.

if (charArray[i] - offset < 0) {
        verschiebung = charArray[i] - offset + 128;
        ...

Here you forgot to put

arrEnc[i] = (char) (verschiebung);

So you should assign verschiebung to arrEnc[i] in the first condition block in the decode method.

answered Mar 28 '19 at 19:10

Anar Amrastanov

385
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it works fine now and that didnt cause the problem! I took the encode part from another site, didnt change the encode and decode method at all, only problem was what I discussed with the other guy above. Thanks anyway! – DJ NoReality TXC_TryhardOne Mar 29 '19 at 20:46
I didnt use the decode method before, now that I used it, it didnt work so I did what you said and it fixed it, thanks ! – DJ NoReality TXC_TryhardOne Apr 01 '19 at 13:57

Cannot decode some passwords?

1 Answers1