This document discusses developing a multi-threaded program to perform a brute force attack to discover a secret key. It will distribute the work across multiple threads, each assigned to try all combinations of a specific key length. It provides sample code for the main classes needed - SecretKey to hold the key, BruteForce as the main class, and WorkerThread to crack combinations for an assigned length in parallel. Students are to implement and submit this password cracking program by the given deadline.

2. ●
An exhaustive search that tries all possible
combinations to discover the secret key.

3. ●
The resources required for a brute-force attack grow
exponentially with increasing key size, not linearly.
# of combinatio ns  number of possible values lengthof key

4. Characters
# Values
Length 2
Length 3
Length 4
Numeric
10
100
1,000
10,000
Alphabet (case
insensitive)
26
676
17,576
456,976
Alphabet (case
sensitive)
52
2704
140,608
7,311,616
Alphanumeric
62
3884
238,328
14,776,336
Alphanumeric +
symbols
92
8464
778,688
71,639,296

5. ●
●
Our task is to develop a multi-threaded program that will
distribute the work load into multiple threads.
Each thread will be assigned to a specific length to
break.

6. TIME
Thread 1
Thread 2
Length = 1
Length = 2
Length = 3
Length = 4
Length = 5
Length = 6
Length = 7
Length = 8
Length = 9
Length = 10

7. 1. Main Thread will create Thread 1 and Thread 2
2. Main Thread will assign odd-numbered lengths to
thread 1, even-numbered to thread 2
3. Main Thread will start Thread 1 and Thread 2
1. Threads 1 and 2 will search from shortest length.
4. Main thread waits for both threads. (use join)
5. Main Ends

8. ●
Use the following template as your guide.
– The SecretKey class will be your shared object
– The BruteForce Class will be your main class
– The WorkerThread will try all possible combinations for its
assigned key size

9. public class SecretKey {
private String key;
public SecretKey(String key) {
this.key = key;
}
public boolean verify(String query){
return query.equals(key);
}
}

10. public class BruteForce {
public char characters[] =
+
("ABCDEFGHIJKLMNOPQURSTUVWXYZabcdefghijklmnopqurstuvwkyz"
""" +
"1234567890" +
"~!@#$%^&*()_+|`[]{};:,.<>/?'|")
.toCharArray();
SecretKey key;
public void initializeKey(){
key = new SecretKey("H!ndiM0Alam"); //sample
}
}

11. public class WorkerThread extends Thread {
SecretKey key;
int keylengths[];
WorkerThread(key, int[] keylengths){
this.key = key;
this.keylengths = keylengths;
}
public void run(){
for(int i = 0; i< keylengths.length; i++){
if(crack(key,keylengths[i])){
break;
}
}
}
public boolean crack(SecretKey key,int length){
//generate all possible keys of length
//code here -- use key.verify();
//if key is verified, print key
}

12. ●
Submit your ME to isubmitmycode@gmail.com with the
following details
– Subject : CS140 ME: Password
– Name, and section
●
Specifications
– The limit for key size is 4 (alphanumeric+symbols);
●
Deadline: Feb 4, 2014