Cracking Passwords in Forensic Investigations - Scholarly ...

This method may be useful for investigators when passwords are
encrypted using weak hashing algorithms.
2.2.2 Brute force
This method of password cracking is used when the encryption algorithm used to
encrypt the password is strong and the password cannot be decrypted. In such a
case, passwords are cracked by guessing. Many tools can be used to guess the
password. Every guess is encrypted by using the same algorithm as the original
password, and the hash value is compared to the hash value of the original
password. If the two match then the guess made is correct and the password has
been recovered (Skoudis, 2007).
In the brute-force password cracking technique, every possible
permutation and combination of the password is tried until the correct password is
found (Dube & Gulati, 2005). Therefore, such an attack will eventually succeed in
guessing the right password. However, this attack is only suitable for short
passwords. For longer passwords, the attack is very time-consuming, since the
sample space of every permutation and combination is extremely large. Thus,
bigger passwords can take many years to recover using this password cracking
technique. Due to these reasons, this form of attack is used as a last resort by
investigators.
2.2.3 Dictionary attacks
This method of password cracking is also used when the encryption algorithm is
strong and the password cannot be decrypted. Therefore, in this case as well, the
password is cracked by guessing. The guess is encrypted and then the output is
compared with the given hash value. If the two match, then the password is
recovered (Skoudis, 2007). In the dictionary attack, the values to be guessed are
taken from the dictionary. Thus, all the words in the dictionary are tried until the
correct match is found (Dube & Gulati, 2005). The dictionary may also be
modified by social engineering or by adding the user‘s personal information. The
personal information could include things such as favourite colour, partner‘s name,
date of birth, place of birth, and any other important information that the user
might use to set their password. Many popular tools such as Password Recovery
Toolkit, John the Ripper, and even L0phtCrack support this password cracking
technique.
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