I am Bojta Lepenye, and first of all, I want to thank the core developers of Hashcat. In my experience, it is quite literally the most capable tool available for offline password cracking across a wide range of use cases.
I have spent the last 4 years (from age 14 to 18) extensively working with Hashcat and the tools surrounding it, and I have documented what I have learned throughout that time (since January 18, 2022) in my first book. During that period, I also had to continuously update and rewrite major sections as the field evolved. One example was the introduction of GPU support for Argon2 and other memory-hard password hashing algorithms, which significantly changed some cracking workflows.
My passion for this book, or its “quick starter,” if you will, came from an ethically conducted penetration test I performed with full authorization at my school. This is something I am both hesitant and quite proud to acknowledge.
At the beginning, I simply wrote down everything I had learned from YouTube videos and online blogs. However, not long after starting my project, I realized I practically knew nothing about password security, and that small 10 to 15 pages I had written would never be enough if someone was looking for a professional guide to cracking passwords.
The other main driving force behind the book was the fact that while researching online, browsing forums, reading academic papers and white papers, watching videos, exploring blogs, inspecting presentations, and examining infographics, I did not find a single source that comprehensively covers and explains everything one needs to understand about offline password cracking. Literally. Not one.
Therefore, I continued my research and learned about password hashing algorithms, the security properties of hash functions, advanced hash cracking techniques, password analysis, attack optimization, and much, much more.
From the very beginning, I wanted to share this knowledge with the community because having access to a resource like this would have helped me tremendously when I first started learning password cracking.
I sincerely hope this work will be useful to both beginners and experienced professionals alike, and I look forward to hearing your thoughts and feedback.
I have also put together a little video to give you a little sneak peek into it. It is on Google Drive. It is the official domain, and you do not need to download anything. Here it is: https://drive.google.com/file/d/13LeysSZO8Mx-LGKt8UQjUGBKOYH...
If you are interested, the book is now publicly available on Amazon, and can be read for free with a Kindle Unlimited subscription: https://www.amazon.com/dp/B0GX36XRCD
Why not put the video on YouTube?
You think this stuff is some kind of secret or illicit knowledge?
The video is just less than half a minute of him flipping through some pages in the book anyway.
Even Claude will help you setup hashcat and co without complaining?
This book is currently not really relevant for me, so I just skimmed the samples on Amazon. I found the technical content to be reasonably accurate and interesting although sometimes a little bit verbose (e.g., the section about 'what is a password') or slightly imprecise. In general, I think this book might have benefited from a thorough copyediting pass. There are quite a few grammar errors and unpolished sentences in the book, e.g.:
> The reason why Linux is imperative is that well, for one, most of the tools we will use, while indeed have builds for other systems, like Windows, in this book we will work with Linux.
Wishing you success and keep on writing!
As for it being imprecise, it doesn't talk about any specific software that has any compatibility issues. It dismisses the topic out of hand.
There being room for improvement is both acceptable and expected.
> "Then there is also the fact that having a fully-fledged graphical desktop environment running in the background at all times is not quite optimal to say the least. 99 percent of the time when cracking passwords, you will be staring at a black terminal filled with white text, so using Windows, which is especially GUI-heavy, is usually impractical unless you are specifically testing something or showcasing some process."
I am reasonably sure that the Windows UI has rather little practical effect on hashcat's speed, and this thread implies the same: https://hashcat.net/forum/archive/index.php?thread-8958.html Also, 99 percent of the time when cracking passwords, I am not staring at a black terminal filled with white text.
(I am generally taking it a little bit personally when the author directly addresses me and tells me what I am probably thinking or doing.)
> "Behind a hash function are a series of complicated mathematical operations that make deriving the input from the output literally impossible."
I'd argue that the mathematical operations themselves are usually not that complicated. More importantly, the whole book seems to be about ways to derive the (probable) input of a hash function from the output. It is not literally impossible.
> "It is important to note, however, that hash functions are not truly random;"
As the author writes elsewhere, hash functions are deterministic and not random at all. Calling them not truly random seems to imply that they are somewhat random.
> "When encrypting a file or any kind of data with AES for example, the program leveraging AES will prompt you for a password. Yes, a password."
Yes, this is a book about password cracking, but there are lots of cases where programs use AES with a computer-generated key and won't prompt you for a password. E.g., TLS.
(Just to reiterate: I am not trying to diminish the author's work, I wanted to suggest ways for improvement. I might be wrong or overly pedantic.)
I think you're not being pedantic enough here. "Probable" is doing some heavy lifting. And the phrasing is "derive the input," which I think is fair to say. The best you can do with a proper hash is discover one or more possible inputs, but you're not deriving them from the output; the output is just used to check the result. The many-to-one nature of a hash precludes determining the exact input.
(It is obvious that one cannot directly derive the exact input - but one can derive potential inputs and then use other means to find the exact one.)
I think it's a canonical way to generalize the audience as in "99 percent of the time when cracking passwords, one will be staring at a black terminal filled with white text" just as in the German "man". So with that in mind maybe you no longer have a reason to be offended :)
Personally, I love abusing commas for comments and shitposting, but they should be avoided in informative resources like books, otherwise, it looks like a word salad. Say your thoughts and ideas with boldness and certainty.
But hey you write better than I did at 18, so I ain't judging. Just trying to provide helpful feedback for you (the op) to improve on.
Too much AI slop, perfect grammar but no substance out there.
This seems like a substance filled book.
Congrats on shipping a book.
I would love to hear more about the process of writing and preparing it for publishing. It's self-published? How did you do the typesetting and the diagrams?
I've hopped through the book and it seems carefully laid out and organized. I may come back at you with questions once I've read further. Cheers.
I work in info sec - I've always been interested in password cracking and hashcat specifically, but have never had the time to devote to really dig into it. I'll check it out.
Well done!
In fact, the people most interested in password cracking are usually criminals.
But good luck with the book. It’s just not a hugely in demand topic.
I'd say that this is a bit relevant to the entire field of cyber security and a good chunk of development roles. If you're not concerned about how password hashing (which is a key component of understanding cracking) works as developer-- I'm not sure what to say. While not all of the in-depth research is probably needed. It's definitely relevant to many technical fields. I work in offensive security and we use tools like this daily in our industry. And no we are not cyber criminals.
Otherwise you do find plenty of people on YT walking you through hashcat. The first YT Video alone has 7 Million views: "how to HACK a password // password cracking with Kali Linux and HashCat"
I wish him luck, great drive to do this, i hope it works out well enough, books are just in general not easy to sell.
People simply didn't /know/ about them/that they existed at all.
I went to a computer/electronics shop in town and asked for them.
The guy told me: "We don't stock them because people don't ask for them."
You mean "lost things" in quotes. Management may have been more concerned about jail time.
probably a lot of ppl lost crypto this way.
Wikipedia states that there were some field unencrypted, sure, but not the critical data.
More people probably lost crypto by forgetting their passwords like a friend of mine. 10k gone
https://en.wikipedia.org/wiki/2022_LastPass_data_breach#Impa...
Many early vaults had an insufficient number of rounds, and though the new account default was upgraded over time, the old vaults never were. So longer time customers were very exposed by this breach. Most impactfully by the incompetence they demonstrated by not upgrading vaults.
Netmux (2019): Hash Crack: Password Cracking Manual¹
James Leyte-Vidal (2024): Ethical Password Cracking: decode passwords using John the Ripper, hashcat, and advanced methods for password breaking²
Daniel W. Dieterle (2024): Password Cracking with Kali Linux³
¹) https://www.amazon.com/gp/product/1793458618
²) https://www.amazon.com/Ethical-Password-Cracking-passwords-a...
³) https://www.oreilly.com/library/view/password-cracking-with/...
online services/anything you can autofill with pw manager:
random generated password as long as possible + MFA like hardware token (UF2)
FDE device/pw manager/anything you can't autofill:
Passphrase containing at least 8 random words (Diceware) + if possible MFA like keyfile or hardware token
Does anyone have a good cloud-hosted password cracker? I can't seem to brute force it, no matter how long I let John the ripper run.
Haven't read the book or used Hashcat, I have a question. Is there anything yet to generate rainbow tables out of password regex?
These are the kinds of real-world constraints where you actually learn how tools like Hashcat work under pressure.
You are going to do big things in the industry!
I have followed a similar path in other technical subjects, and have authored a couple of books on those journeys. I look forward to reading yours.
Some people have brought up style and structure issues with your book.. try to take this in stride. Writing for publication is its own whole thing, and involves a lot more than just putting ideas to print. Creating text that conveys the spirit, personality, and information that you want it to is nontrivial, and it takes time and practice to master. It’s easy, as a reader, to feel the rough spots in a literary work… but that does not mean that the reader would do any better when confronted with writing a book level tome, so hear the critique but don’t overthink the critic.
Even though writing well was a side quest to my otherwise very technical focus, I found a joy in developing my literary voice… and I would encourage you to keep uncovering yours.
Don’t be bullied into writing “correctly”. If you want to ponder the senselessness of life you can read one of millions of “correctly” written papers that will have you wanting to end it all just so you don’t have to go on. In these informative but wasted pages you won’t find a shred of the author, and only find yourself bored by the subject that so enthralled them to spend a thousand hours or more writing about it. What a wasted opportunity. They became so focused on writing correctly that they lost their voice entirely. Their writing may inform, but it will rarely inspire.
In these little bits of your writing I have skimmed so far, there’s plenty of warts but I feel you in the work. Your passion is contagious, and I am encouraged to learn. Sure, work out the warts, but don’t be bullied into writing “correctly” by sticking to formality and convention.
Writing is about informing, inspiring, and guiding the frame of mind of the reader. Your work does that because your voice shines through. Sure, it could be easier to read, sometimes clearer, and you should work on that if you want to, but don’t sacrifice your voice in the process. The best written work has a definite personal opinion on how to write a voice, and it’s usually not the “correct” way.
Humans writing like humans is what makes writing worthwhile in the third industrial age. Frolic in your humanity and keep up the good work. Don’t let the well intentioned bastards keep you down, especially if they have a point.