Your country is at war and your enemies are using a secret code to communicate w
ID: 3710746 • Letter: Y
Question
Your country is at war and your enemies are using a secret code to communicate with each other. You have managed to intercept a message that reads as follows:
:mmZdxZmx]Zpgy
The message is obviously encrypted using the enemy's secret code.You have just learned that their encryption method is based upon the ASCII code. Individual characters in a string have encoded using this system. For example, the letter "A" is encoded using the number 65 and "B" is encoded using the number 66, and so on.
Your enemy's secret code takes each letter of the message and encrypts it as follows:
If (OriginalChar + Key > 126) then
EncryptedChar = 32 + ((OriginalChar + Key) - 127)
Else
EncryptedChar = (OriginalChar + Key)
For example, if the enemy uses Key = 10 then the message "Hey"would be encrypted as:
ASCII Conversion
H --> 72
e --> 101
y --> 121
Encrypted H = (72 + 10) = 82 = R in ASCII
Encrypted e = (101 + 10) = 111 = o in ASCII
Encrypted y = 32 + ((121 + 10) -127) = 36 = $ in ASCII
Consequently, "Hey" would be transmitted as "Ro$."
Write a java program that decrypts the intercepted message. You only know that the key used is a number between 1 and 100. Your program should try to decode the message using all possible keys between 1and 100. You can assume that the original message consists entirely of ASCII codes that represent only printable characters. Your program should try to decode the message using all printable characters. Your program should try to decode the message using all possible keys between 1 and 100. When you try the valid key, the message will make sense.For all other keys, the message will appear as gibberish. Since there are only 100 keys this would obviously be a pretty crummy encryption system. This programming Project will require you to explore a bit on your own how to convert from char to a number, process the number, then convert it back to a char. See Chapter 2 for Strings methods. You will want to use charAt().
Important: Note that the secret code has a so you will need to escape encode it by using \ if you hard-code it in your program.
Explanation / Answer
package hashcode;
public class decrypted
{
public static int Main()
{
final String EncryptedChar = ":mmZ\dxZmx]Zpgy";
int key;
byte OriginalChar;
if (OriginalChar + key > 126)
{
EncryptedChar = 32 + ((OriginalChar + key) - 127);
}
else
{
EncryptedChar = (OriginalChar + key);
}
for (key = 0; key <= 100, key++)
{
System.out.print("Key: ");
System.out.print(key);
System.out.print(" Decoded Message: ");
System.out.print(EncryptedChar);
}
system("Pause");
return 0;
}
}
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