How does John the Ripper (John) guess passwords?

Question

John sends passwords to the remote server and waits for a response.
John guesses one letter at a time until it has the full password
John hashes the guess and compares it to the list of password hashes to be cracked
John breaks the hashes by reverse engineering the algorithms

Answer 1

John the Ripper (often abbreviated as "John") primarily guesses passwords by hashing the guesses and comparing them to the list of password hashes to be cracked. Here’s a breakdown of how it works:

1. Password Hashing: When users create passwords, those passwords are often hashed using cryptographic algorithms and stored in a secure manner. John the Ripper takes known password hashes and attempts to find the original passwords that created those hashes.

2. Guessing Mechanisms: John utilizes various methods to generate password guesses. This includes dictionary attacks (using a list of common passwords), brute-force attacks (trying all possible combinations), and more sophisticated techniques like incremental mode or using rules to modify existing guesses based on patterns.

3. Comparison: For each guessed password, John hashes the guess using the same algorithm that was used to create the original hashes. It then compares the newly generated hash with the stored hashes. If there’s a match, John has successfully cracked that password.

4. Utilizing Algorithms: John does not reverse-engineer algorithms; rather, it relies on knowing the hashing algorithms used (e.g., MD5, SHA1) to generate the corresponding hashes for guessed passwords.

So, the correct option is: John hashes the guess and compares it to the list of password hashes to be cracked.