Dictionary Attack The dictionary attack utilizes wordlists to have a go at our target password. Let’s quickly take a look at some common attack types and techniques. However, John also offers Single crack mode and custom rules. The most commonly used attack type is dictionary attack, which we use to brute force the target password. Uses and Attack Types With John you can also crack Windows Authentication Hashes, /etc/shadow/ hashes, password protected. This is what John leverages to identify the hashes when using a dictionary type attacks, when going through a given list and hashing the words inside it so that it can compare it to our target password. Luckily, it's enough to determine the hashing algorithm that was used (this would be the NP part of the P vs NP problem), and compare that hashed value against the hash of the same input that we have previously calculated using the same algorithm, and check to see if they are equivalent. We can’t use the calculated hash value – output, to reverse the hash value. To explain this we would need a mathematician, specifically a cryptographer nevertheless, the basic idea is that the hash algorithm is intended to operate one way only. What makes them secure, and computationally impossible to reverse, is the underlying mathematical (cryptographic) background, at the core of the concept, known as the P vs NP problem. įrom this we can infer that we will always get an output of 64hexadecimal characters, or 32 bytes which is exactly 256 bits of data. Īs an example, take my name – acephale as an input string and pass it through a SHA256 algorithm, and we get the following string of characters:ī10a0dd841ddffef3c0e8aa683c7d9c97bdc048f8183ed41274e64e4faa3899d.
Some more popular examples are: NTLM, MD4, SHA512. We do so by passing our original data through an algorithm – hashing algorithm. Hashes Hashing, most simply put, is the act of taking a piece of data (of any length) and representing it in another shape, that is of fixed length. For Windows, there’s also the Hash Suite, developed by a John the Ripper Contributor. It is also worth mentioning that John will work on all of the three most common operating systems – Windows, MacOS, and Linux-based distros. John is extremely versatile, most importantly, it is extremely fast, with a really big range of compatible types of hashes, not just the most common ones like SHA1, SHA256, MD5, etc. Intro John The Ripper, or John for short, is one of the most well known password and hash cracking tools out there.
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