![]() ![]() In this process, a user supplied password is automatically converted to all uppercase, padded to fourteen characters (this is the max length for an LM hashed password), and split into two seven character halves. Perhaps the biggest weakness in the LM hash is in the creation of the DES keys. In short, it’s another encryption standard that has fallen victim to modern computing power and can be cracked in no time at all. Since this, DES has been considered insecure and has since been replaced with Triple-DES and AES. This came to a head in 1998 when the Electronic Frontier Foundation was able to crack DES in about 23 hours. DES was considered secure for many years but came under scrutiny in the nineties due to its small key size of only 56-bits. DES originated from a 1970s IBM project that was eventually modified by NIST, sponsored by the NSA, and released as an ANSI standard in 1981. The first of these is that the encryption is based on the Data Encryption Standard (DES). LM stored passwords have a few distinct disadvantages. In practice, the password “PassWord123” would be converted as follows:įigure 1: A password transformed into an LM hash The two 8-byte ciphertext values are combined to form a 16-byte value, which is the completed LM hash.Each DES key is used to encrypt a preset ASCII string ( #$%), resulting in two 8-byte ciphertext values.These values are used to create two DES encryption keys, one from each half with a parity bit added to each to create 64 bit keys.The new password is split into two 7 character halves.The password has null characters added to it until it equals 14 characters.The user’s password is converted into all uppercase letters.The LM hash of a password is computed using a six-step process: However, it is disabled by default for Windows Vista and Windows 7. These newer operating systems still support the use of LM hashes for backwards compatibility purposes. The LAN Manager hash was one of the first password hashing algorithms to be used by Windows operating systems, and the only version to be supported up until the advent of NTLM used in Windows 2000, XP, Vista, and 7. A hash is the result of a cryptographic function that takes an arbitrarily sized string of data, performs a mathematical encryption function on it, and returns a fixed-size string. These are LAN Manager (LM) and NT LAN Manager (NTLM). Windows-based computers utilize two methods for the hashing of user passwords, both having drastically different security implications. After demonstrating how to crack Windows passwords I will provide some tips for ensuring you are not vulnerable to these types of attacks. The purpose of this article is to educate you on how Windows creates and stores password hashes, and how those hashes are cracked. Even if attackers do not have physical access to a machine they can often access a server through the remote desktop protocol or authenticate to a service via an outward facing web application. Passwords tend to be our main and sometimes only line of defense against intruders. ![]() If you would like to read the next part in this article series please go to How I Cracked your Windows Password (Part 2). ![]()
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