Cracking Passwords in Forensic Investigations - Scholarly ...

length and is nonsensical in nature. It is derived from the original password by
passing it through a one-way hash function (Raval & Fichadia, 2007).
A one-way hash function can derive the password hash by using the
password as a value for the function. However, after the hash is calculated, it is
impossible for the function to be reversed to derive the original password from the
password hash. Also, the one-way hash function is designed to be ‗collision-free‘,
such that different passwords generate different hash values (Raval & Fichadia,
2007). In order for authentication to take place, the user enters his or her password,
which is passed through the one-way hash function. If the output generated
matches the stored hash value, then the user is allowed access. This mechanism is
demonstrated in Figure 2.1.
Some operating systems generate the password hash by passing the
password along with an additional value called a ‗salt‘ through the hash function
to increase randomness. Thus, a ‗salt‘ is a short, random string of characters that
is appended to the password to increase security (Salomon, 2006). One of the
most common values used as a salt is the username (Raval & Fichadia, 2007).
―world‖
(wrong password)
Generate Hash Password Hash
Store
653DAF!%$!!A1$413 1$%!#15769AAFDS!#$
No
Do
hashes
match? Yes
Access Denied Access Granted
Figure 2.1: Password hashing and verification (Raval & Fichadia, 2007, p. 180)
9