rev/java-rev-2 (#21)

* init

* chall

* solvepath

* solvepath fixes

* make nominally easier with a hint

---------

Co-authored-by: mud-ali <[email protected]>

java-rev-2/RevTwo.java

@@ -0,0 +1,30 @@
+import java.util.Scanner;
+
+public class RevTwo {
+    public static void main(String[] args) {
+        System.out.println("Enter the password: ");
+        Scanner scanner = new Scanner(System.in);
+
+        String line = scanner.nextLine();
+
+        if (checkPassword(line)) {
+            System.out.println("That's the right password!");
+        } else {
+            System.out.println("That's the incorrect password!");
+        }
+
+        scanner.close();
+    }
+
+    public static boolean checkPassword(String passwordGuess) {
+        int[] nums = {7267, 6113, 11757, 7152, 7675, 6345, 9823, 11463, 8821, 12339, 8019, 6739, 5983, 11476, 10344, 11057, 11603, 5087, 8791, 11956, 12115, 11982, 4820, 10719, 8787, 6835, 9059, 6901, 11090, 5605, 7677};
+
+        for (int i = 0; i < passwordGuess.length(); i++) {
+            if ((int) passwordGuess.charAt(i) != nums[i] % 128) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+}

java-rev-2/chall.yaml

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+name: Java Rev 2
+categories:
+  - rev
+value: 100
+flag: camp{I_Gu3SS_Th1S_W4SNT_S3cuRe}
+description: |-
+  After your last break-in, my friend informed me that he made it almost impossible to solve.
+  Can you still find the password? 
+hints:
+  - Do you know what ASCII is?
+  - What does the % do?
+files:
+  - src: RevTwo.java
+authors:
+  - Jack Crowley
+visible: true

java-rev-2/solve.md

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+# Java Rev Two
+
+This Java Rev challenge has an array with all of ascii values of the flag, however, they seem a little bit too high to fit into the normal 128 values. 
+
+This is where `modulus` or the `%`, which acts sort of like a `division` statement. However, instead of returning the evaluated results, it gives us the remainder. In this case, it takes `nums[i] % 128`, which means that it gets the number from the array and then takes the remainder of that number after being divided by 128. 
+
+For example, 6113 divided by 128 is 47, remainder 97. As such, 6113 mod 128 = 97
+
+To solve this problem, you must first delete the `return False;` in the `checkPassword`, which enables the program to keep going even if the first character is wrong.
+
+Then you must put a print statement inside the for loop which prints the correct character of the flag, such as:
+
+```
+System.out.print((char) (nums[i] % 128));
+```
+
+Note that `(char)` will display the corresponding character for the number.
+
+Once you run the program, input a long and random input such as:
+
+```
+aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+```
+
+which will produce the correct flag in the terminal.