CODEWITHSUNDEEP
java
Nathan Kim
Nathan Kim

Reputation: 21

How do I change my encryption code so that it will only encrypt the given string, and not encrypt what was previously encrypted?

My code encrypts the previously encrypted phrase in an inputted sentence. I want it so that it encrypts only the letters v, m, g, and b in the original string, not the previously encrypted letters, if that makes any sense. So with a string such as "Very good", it would encrypt the letter v into the correct phrase, but then it would find the letter 'b' within that encrypted phrase, then further encrypt it, which is want I don't want. And obviously the decryption wouldn't work as well, because it needs the specific phrase to turn it back into the correct letter, but it can't because the phrase has been encrypted even further than it should have.

I've tried to change the order of what letter gets encrypted first, hoping that it would avoid conflicts, but that hasn't worked at all.

Crypto Class

public String encryptdSntnc;
public String decryptdSntnc;
public String sntnc;
public String encrypt(String sntnc)
{
    String encrypt1 = sntnc.replace("v", "ag',r");
    String encrypt2 = encrypt1.replace("V", "ag',r");
    String encrypt3 = encrypt2.replace("m", "ssad");
    String encrypt4 = encrypt3.replace("M", "ssad");
    String encrypt5 = encrypt4.replace("g", "jeb..w");
    String encrypt6 = encrypt5.replace("G", "jeb..w");
    String encrypt7 = encrypt6.replace("b", "dug>?/");
    encryptdSntnc = encrypt7.replace("B", "dug>?/");
    return encryptdSntnc;
}

public String decrypt(String encryptdSntnc)
{
    String decrypt1 = encryptdSntnc.replace("dug>?/", "B");
    String decrypt2 = decrypt1.replace("dug>?/", "b");
    String decrypt3 = decrypt2.replace("jeb..w", "G");
    String decrypt4 = decrypt3.replace("jeb..w", "g");
    String decrypt5 = decrypt4.replace("ssad", "M");
    String decrypt6 = decrypt5.replace("ssad", "m");
    String decrypt7 = decrypt6.replace("ag',r", "V");
    decryptdSntnc = decrypt7.replace("ag',r", "v");
    return decryptdSntnc;
}

Tester Class

    Scanner kbReader = new Scanner(System.in);
    System.out.print("Enter a sentence that is to be encrypted: ");
    String sntnc = kbReader.nextLine();

    Crypto myCryptObj = new Crypto();
    String encryptdSntnc = myCryptObj.encrypt(sntnc);
    System.out.println("Encrypted sentence = " + encryptdSntnc);

    String decryptdSntnc = myCryptObj.decrypt(encryptdSntnc);
    System.out.println("Decrypted sentence = " + decryptdSntnc);

What I expect is if you type in "Very good", the encrypted sentence would be "ag',rery jeb..wood", and the decrypted sentence would be "Very good".

But instead, I get "ajedug>?/..w',rery jedug>?/..wood" for the encryption, and "ajeB..w',rery jeB..wood" for the decryption, using the same "Very good".

Upvotes: 2

Views: 127

Answers (1)

dave
dave

Reputation: 11985

Your approach to your encryption will not give you what you desire. You want the modifications to affect the original string. However, your step-by-step approach means you get something different. Let's consider just the first two changes:

Very good

becomes

ag',rery good

based on the first pair of rules for replacing v or V.

So encrypt2 has this value and then you apply the next pair of rules for replacing g or G to this value. This has the effect of replacing the first g which is not from the original string, but has been added by the first step. Thus encrypt5 has the value:

ajeb..w',rery good

Your encryption will continue in this fashion and you get the undesired result.

You might want to try a loop over your original string instead. Something like:

public String encrypt(String sntnc) {
    StringBuilder encryptdSntnc = new StringBuilder();
    for (char c : sntnc.toCharArray()) {
        c = Character.toLowerCase(c);
        switch (c) {
            case 'v' :
                encryptdSntnc.append("ag',r");
                break;
            case 'm' :
                encryptdSntnc.append("ssad");
                break;
            case 'g' :
                encryptdSntnc.append("jeb..w");
                break;
            case 'b' :
                encryptdSntnc.append("dug>?/");
                break;
            default :
                encryptdSntnc.append(c);
                break;
        }
    }
    return encryptdSntnc.toString();
}

Decryption will be more complicated as you need to match strings and replace them with a character. However a similar approach using a loop should be possible. Instead of a switch statement, you could search for each string that can be replaced by a character.

Upvotes: 1

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