Tptacek's Review of "Practical Cryptography With Go"

https://gist.githubusercontent.com/anonymous/3cc34251e501c2c8ffb7/raw/cf9ff4e7ce13985458b240980e91202ac732b4e6/Practical+Cryptography+in+Go+

by babawere • 12 years ago

284 250 12 years ago

gist.githubusercontent.com

zurn• 12 years ago

This is a good illustration of how, 1) crypto is hard 2) real-world cryptosystem design & implementation is hard and 3) teaching the aforementioned is hard.

I read Schneier's & Ferguson's Practical Cryptography years ago, the only thing I remember about it is the "don't try this at home" message.

Nursie2• 12 years ago

I recommend Dan Boneh's coursera course, Crypto I, to get a good (basic) grounding in how some of this stuff works. He shows just how easy it is to break bad crypto systems in unexpected ways, and he does it by leading you through 5he attacks and getting you to implement some.

Was rather impressed...

mehrdada2• 12 years ago

I read Schneier's & Ferguson's Practical Cryptography years ago

I cannot take anyone who advocated MAC-then-Encrypt, in 2010, seriously (in the book Cryptography Engineering: Design Principles and Practical Applications by Niels Ferguson, Bruce Schneier, Tadayoshi Kohno).

The school of cryptography they subscribe to seems to be "crypto is black magic; this is tried and it works and it is pretty much secure because I feel it is secure; experience is everything; proofs can have bugs too" as opposed to a more principled, analytical, methodical, provable security.

This is especially problematic in pedagogical contexts, because the learners, by definition, do not have much experience or calibrated feelings, so they'll be lost or have to copy the design decisions of the authors without taking into account the contexts or that they might be flat wrong. That approach indeed implies the natural advice to someone who wants to learn will be "don't try it at home".

icambron• 12 years ago

"Don't try this at home" is good practical advice for building real systems that have real users. It's terrible pedagogy, though. You have to learn somehow, and trying it at home is actually how you do that.

stcredzero10• 12 years ago

Well, the message should be, do try this at home, as an exercise, but don't put it into production!

VMG• 12 years ago

Coursera's "Cryptography I" pays off again -- I know most of the words!

StavrosK7• 12 years ago

Still waiting for Crypto II :(

Nursie2• 12 years ago

Me too. How long overdue now? 2 years? Crypto 1 was awesome, am impatient to do more!

smackfu• 12 years ago

It says it is scheduled for July 21. Don't know how accurate that is.

jacquesm4• 12 years ago

I'll take it on faith that Thomas really wrote this (it's his style), but would the real Thomas 'H' Ptacek please acknowledge that he indeed wrote this (it is labeled 'anonymous').

nairteashop• 12 years ago

He actually posted this link yesterday as a comment: https://news.ycombinator.com/item?id=7581868

jacquesm4• 12 years ago

Ah cool! Thanks. It seemed a little strange to have his name used so prominently in the title here linked to something that did not have his name attached to it or in any other way easily associated. Call me paranoid ;)

dbaupp• 12 years ago

From the original discussion: https://news.ycombinator.com/item?id=7581868

dylz• 12 years ago

'anonymous' just means that the user was not logged into github when posting the gist.

zatkin2• 12 years ago

For those of you who don't know what the acronyms stand for, I've compiled a list, in order by their appearance:

  AES   - Advanced Encryption Standard
  CBC   - Cipher Block Chaining
  PKCS  - Public Key Cryptography Standards
  SHA   - Secure Hashing Algorithm
  MAC   - Message Authentication Code
  PBKDF - Password-Based Key Derivation Function
  NIST  - National Institute of Standards and Technology
  FIPS  - Federal Information Processing Standard
  KDF   - Key derivation function
  CTR   - Counter Mode
  RSA   - Rivest Shamir Adleman (last names of each creator of the RSA algorithm)
  OAEP  - Optimal Asymmetric Encryption Padding
  PSS   - Probabilistic Signature Scheme
  ECDSA - Elliptic Curve Digital Signature Algorithm
  PS3   - Playstation 3?
  DH    - Diffie-Hellman key exchange
  ECDH  - Elliptic curve Diffie-Hellman key exchange
  TLS   - Transport Layer Security

eproxus• 12 years ago

I usually make it a habit to spell out abbreviation the first time I use them and include the abbreviation in parentheses, like Transport Layer Security (TLS). Later, after the first introduction I can safely assume people know it, like TLS.

Even for technical documents, if you expect your target audience to be familiar with the domain, nobody remembers every abbreviation every time. It also helps new readers to quickly familiarize themselves with the material (and might even help a few understand more than they would have done without expanded abbreviations).

tomp• 12 years ago

This hardly makes any sense:

  - for the readers who already know the abbreviation, it's a waste of space and time
  - for readers who don't, the words won't tell them much either - Transport Layer Security tells you about nothing about what TLS really is - besides, for those who are really interested, they can always look it up on Wikipedia (that way, they will actually understand it).

mnordhoff• 12 years ago

What I have trouble with is the spelled out versions. Every time I see some stupid newspaper article that says "HyperText Markup Language" or whatever, it takes my brain two or three seconds to process it and go "oh, duh, HTML".

dfc• 12 years ago

Welcome to HN. I see that you are new here so I would like to give you a little friendly advice. If you have to make a long list like this on HN use the pre/code formatting (two spaces at begining of line). Long lists like this take up a ton of space. I have a sneaking suspicion this is the a deliberate design choice so that people link to reference resources and use the comments for discussion. Compare:

AES - Advanced Encryption Standard

CBC - Cipher Block Chaining

PKCS - Public Key Cryptography Standards

SHA - Secure Hashing Algorithm

MAC - Message Authentication Code

PBKDF - Password-Based Key Derivation Function

  AES - Advanced Encryption Standard
  CBC - Cipher Block Chaining
  PKCS - Public Key Cryptography Standards
  SHA - Secure Hashing Algorithm
  MAC - Message Authentication Code
  PBKDF - Password-Based Key Derivation Function

zatkin2• 12 years ago

You. I like you. Thank you! I've updated the list. I didn't see anything on the posting help page about putting two spaces in front to make it pre/code formatting. (Or maybe there was a second page I didn't look over.)

Edit: I just double-checked the help page and saw the note about code formatting. My apologies for overlooking that!

simonw• 12 years ago

The one problem with doing this is that it causes people reading HN on an iPhone to have to scroll from side to side for every line of text, since preformatted text doesn't word-wrap on small screens.

JonnieCache• 12 years ago

PS3 is correct. That was a particularly amusing episode, well worth looking up the full story.

EricDeb• 12 years ago

http://vimeo.com/18274128#t=28m28s

exDM69• 12 years ago

Nice that you composed this list but quite honestly, it isn't very helpful to know what the letters in the acronyms stand for without knowing what these things actually are.

Take AES for example, "Advanced Encryption Standard" doesn't really mean anything. AES is a block cipher, also known as Rijndael. CTR and CBC are block cipher modes. RSA is a public key cryptosystem, etc. The same applies for most of these things in the list.

So if someone doesn't know what these things stand for, they're going to have to go to Wikipedia to check it out anyway, the words behind the acronym are almost as confusing as the acronyms themselves.

mhaymo2• 12 years ago

"Message Authentication Code" is a lot easier to google for than MAC, and more meaningful in itself too. I found the list helpful.

Rubikan• 12 years ago

Yeah, but searching for the actual word is much easier than searching the acronym. Take MAC for example (tried out with german google, so your experience may vary).

I get a cosmetics site, apple.com and store.apple.com, wikipedia article about the mac adress and a clothing site. Message Authentication Code is nowhere to be found.

Yes, I took one of the harder ones, AES is on the first position, but still it is nice to know the words behind an acronym.

jensC• 12 years ago

I think the list was helpful as well. I know quite a few of those acronyms and what hey mean, but a few I did not know.

austinz2• 12 years ago

I see the implementation of cryptosystems as an engineering endeavor little different than designing, for example, a commercial airplane, a bridge, or a radiation therapy machine. In all cases you have a system whose failure can result in anything from monetary loss to death (for an example of the latter, faulty cryptographic software used by dissidents in repressive countries). In all cases you use a combination of rigorous testing and analysis from first principles to try and isolate potential weaknesses. In all cases you want to ensure the people who worked on the system knew what they were doing and put the right amount of due diligence into ensuring the system works correctly.

Unfortunately, not even widely used, highly trusted implementations work right all the time. A out-of-bounds memory bug introduced by an insufficiently vetted commit opened up a serious flaw in OpenSSL. On a much, much smaller scale, I once had the misfortune of working with an old version of Microchip's PIC18 AES library, which had some serious issues that made it nonfunctional for anything more complex than the toy sample app it shipped with. But with enough exposure these problems are eventually exposed and fixed. Would a world where everyone rolled their own bespoke, ad-hoc SSL implementations be more secure? I doubt it.

In the end, I think there needs to be a cultural shift. People shouldn't be discouraged from building their own crypto for fun and learning, but they should be discouraged from deploying it for any application where real security is required - at least not before undergoing rigorous analysis. One of the first things Dan Boneh teaches in his Crypto I class is that you should think very long and hard before implementing your own cryptosystems (i.e. don't do it), because getting it right is hard, and getting it even the slightest bit wrong tends to make it useless. And when you consider that people's livelihoods (their personal information, their money) and even lives might be jeopardized, taking responsibility as an engineer becomes of paramount importance. Crypto just doesn't lend itself to a "build an MVP, get it working, move fast and break things" mindset.

lkozma• 12 years ago

The reason why crypto might be even harder than the other engineering tasks you mention is that in those the "adversary" is indifferent, not actively trying to exploit every loophole you might have left. You might build a bridge that has some small weakness, but no-one will come and stack weights in the exact pattern that exploits the weakness and makes the bridge collapse.

dasil003• 12 years ago

Beyond that, failure of a bridge or an airplane is not likely to go unnoticed. Every failure will be investigated, documented and studied. Crypto failure by contrast can just easily be silent, deadly, and continuously unnoticed for extended periods of time.

jasonlotito• 12 years ago

Engineering does have to deal with real adversarial threats.

Just on example I've found: https://www.nae.edu/Publications/Bridge/Terrorism/AnEngineer...

"The second relates to the design of structures. It is time for engineers and architects to get together to devise new structural forms that offer a higher degree of protection not only against terrorist attack, but also against other hazards. There is much to be learned from what happened in Nairobi and Dar es Salaam, in Oklahoma City, and at the World Trade Center. Similarly, retrofitting of existing structures needs to be studied systematically, as it can reduce, at modest or virtually no cost, the potential for damage."

jessaustin• 12 years ago

Yes gravity and metal are more predictable than a creative adversary:

http://wondermark.com/406/

rkangel2• 12 years ago

I see the implementation of cryptosystems as an engineering endeavor little different than designing, for example, a commercial airplane, a bridge, or a radiation therapy machine.

Couldn't agree more. The problem is that for any bridge that gets used, every structural engineer signing off is going to have been educated and experienced to the extent that they are Chartered (or equivalent), the plans for the bridge have to be approved by planning authorities and a thorough documentation and review process has been gone through, before the first drop of concrete has been poured. And once its up, it's tested, and inspected regularly. As every engineer on the project has necessarily been educated they know how hard it is and what the pitfalls are.

Bad crypto results from the fact that there is no need for any of the above requirements to be met. Any old engineer might think they can produce a good implementation, design it, put it into production and have systems secured by it, without being aware of the potential problems they're causing.

The free world of the internet is a wonderful thing, but regulation isn't entirely a bad thing either.

jacquesm4• 12 years ago

How will regulation take care of bad crypto? Even experts get it wrong with some regularity (of course not as often as noobs, but still).

logicallee2• 12 years ago

I see the implementation of cryptosystems as an engineering endeavor little different than designing, for example, a commercial airplane, a bridge, or a radiation therapy machine.

I disagree with you completely and absolutely. Your bridge in Boston isn't going to collapse the moment a researcher sitting in his bathtub in Tel Aviv has a eureka moment.

But if that eureka moment results in a preimage collision in a secure hashing algorithm, that hashing algorithm is broken for everyone all over the world forever. (Practically, as soon as the collision is public knowledge). Cryptographers have to actively seek out this information.

That's why MD5 is deprecated, even though the weakness is weaker than the one I've just stated. (It's just a chosen prefix collision that can be done today - a preimage [chosen hash] attack still takes nearly the full search space.)

Security is applied mathematics, the way engineering is applied physics. But the laws of physics don't change on an annual basis, or the way in which they change is too low-level to apply to engineering, whereas the laws of applied mathematics do.

Systems administrators have to keep up to date on an even more active basis, in some cases needing to patch any system within 48 hours of a public disclosure.

So I simply disagree that as an engineering endeavor implementation of cryptosystems is in any way similar to any other form of engineering.

In fact, for the particular example I used in the above case (a hash), the very existence of the operation is an open problem. ("The existence of such one-way functions is still an open conjecture", Wikipedia.)

What other branch of engineering relies on laws that may well be false?

izacus• 12 years ago

Well, the lack of good documentation for libraries is also hugely problematic.

For example, I'd call OpenSSL documentation "criminally bad" to the point where it actively tries to coax the user into making a mistake - there is no central point of good practices for common use cases (e.g. sending a AES256-CBC encrypted block of data securely with shared key, using pub/private key, etc.) and the docs regulary don't mention the proper way of initializing different datastructures and modules (like RNGs) when they're mentioned. Even finding out how to properly initialize everyting to do a standard PBKDF#2 password derivation is a huge chore that requires reading through tons of badly formatted documents (or copying a random piece of code from StackOverflow which may or may not be secure). That makes even highly secured libraries a minefield where you can easily introduce huge security flaws without even knowing that you did so.

And as long as the excuse for that is "well, you just need few years of studying all crypto background" we'll be seeing security breaches everywhere - developers mostly just aren't prepared to spend so much time learning the crypto field or spend alot of money on security experts. In the big picture that's a huge issue - too many devs just opt to copy random pieces of code from StackOverflow, which can have very glaring security flaws or are simply not secure for the devs usecase.

a80002• 12 years ago

What I don't understand why most crypto libraries are then implemented in an inherently unsafe language. I feel something like the secure subset of Ada would have been much more apropriate.

phpnode• 12 years ago

Because to be usable it needs to be fast (and portable), and for a long time those constraints basically meant C - possibly not any more.

But let's not kid ourselves, reimplementing a library the size of OpenSSL in a new language, or even the same one, is not a trivial matter. We're talking about a $10m+ investment, who's going to pay?

laichzeit0• 12 years ago

Does Tptacek have a list of books/articles he would recommend to the Crypto neophyte? I'm talking about books which could be considered de facto standards like Knuth's TAOCP or Steven's TCP/IP books.

duongkai• 12 years ago

Let check the profile of tptacek. In his profile, there is a his reading list. Grab some book about cryptography.

Or you can browse his blog, Practical Cryptography or Cryptography Engineering may be a good start.

olalonde• 12 years ago

He replied to this question here: https://news.ycombinator.com/item?id=7581885 (http://sockpuppet.org/blog/2013/07/22/applied-practical-cryp...)

obilgic• 12 years ago

How do we know that this is written by tptacek?

adamnemecek• 12 years ago

He posted it in a comment yesterday, read the rest of this thread.

GuiA• 12 years ago

From tptacek's comment, it sounds like the author of the book may just be an inexperienced practitioner of cryptography who's only crime is to be too eager to spread what they've learned.

Someone who picked up the basics from a few Wikipedia articles here, a few papers there, a couple open source projects here and there... they're smart, so they're not completely clueless about the field, but they just don't have the experience to see where they fall short, the industry know-how, and so on.

I feel like instances of this in the tech community are not too rare, and it's a consequence of the internet: anyone can publish a book and distribute it all over the world now. It's worth keeping in mind that while harm is being done through the spread of false information, what's most important is to educate them, see this as a teachable moment, so they can become productive experts and modify their message to be fully correct. Of course, it requires them to be open minded of their shortcomings: but it can be done.

PS: I have no clue who the author of Practical Cryptography With Go is.

zura• 12 years ago

At least I got an impression that Tptacek's most points are easily accountable so lets wait for Practical Cryptography With Go, 2nd Ed. :)

dsymonds• 12 years ago

An "inexperienced practitioner of cryptography" should not be writing a book about cryptography. It's great that such a person is learning, but you shouldn't be trying to pass on such information at that stage.

(I don't know the author either)

chipaca• 12 years ago

Remember that being wrong about something feels exactly the same as being right about something, so (extending "being wrong" to "being ignorant") unless somebody tells them they won't know they still have stuff to learn.

Spooky23• 12 years ago

An experienced publisher shouldn't be printing said book either.

mrhonza• 12 years ago

I have no clue who the author of Practical Cryptography With Go is.

https://leanpub.com/gocrypto

yukichan2• 12 years ago

As bad as it may seem I've found that saying incorrect things results in more learning than staying quiet so I often say incorrect things but things I think are true. I'm embarrassed when I'm wrong but I always learn from it. I also ask "why?" a lot and "what is that?" if it makes sense to (or just Google it later). I learn this way. It helps solve ignorance. It doesn't make me a faster thinker which is something I may not be able to fix, and it doesn't help improve my motivation to learn more which I need to do more of instead of playing video games or creating things.

kbenson• 12 years ago

Writing a book to teach other people should not be considered first and foremost a way to learn a subject. You may learn when corrected, but at the expense of the readers that read the mistakes and did not see corrections. This is more important the more advanced or important the subject.

I would not write a book on structural engineering to learn the subject or become an expert. The stakes for the misinformation being spread are high.

tptacek30• 12 years ago

I am exactly the same way.

gojomo2• 12 years ago

Brutal but also in some ways a gift to the author/publisher. Paired with the 1st edition, it cures the major defects.

And, if the criticisms can be addressed, in both specifics and perspective, for a future edition, they'll have a hardened book... almost sure to earn another updated expert review ("is it fixed?") at that time.

vacri• 12 years ago

Brutal, but definitely a godsend to the author. Ptacek writes mostly neutrally, concisely, and clearly, pointing out errors and often putting in how to fix them. There's a very small amount of "I can't believe..." statements in there, but they're pretty soft and quite reasonable given his background. A publisher would love to have this kind of technical review done on their manuscripts.

oinksoft• 12 years ago

The last paragraph of this review is in poor taste. The most cursory research into the author's "CryptoBox" shows that indeed this project is inspired by NaCL.

appleflaxen• 12 years ago

I found the last paragraph helpful. It's great that NaCL inspired him, but why use the same name for something different? Libraries and packaging are hard enough without sound-alikes.

riffraff• 12 years ago

can someone explain this?

    * This book, I am not making this up, contains the string: "“We can use ASN.1 to make the format easier to parse".

Last time I had something to do with ASN.1 was years ago but it seemed to work well, libraries were full featured and cross-language interop was ok. What am I missing that makes ASN.1 bad ?

Or is the critique to an attempt to write a custom ASN.1 serializer/parser?

_pmf_• 12 years ago

Last time I had something to do with ASN.1 was years ago but it seemed to work well, libraries were full featured and cross-language interop was ok. What am I missing that makes ASN.1 bad ?

Didn't you know? If a web developer out of high school cannot read a format at first glance, it's obviously over-engineered and useless and anyhow everybody should always use JSON anyways.

slavak• 12 years ago

tptacek is hardly a web developer straight out of high school.

_delirium3• 12 years ago

ASN.1 parsers have been the source of a decent number of exploits, producing a bad reputation. Although doing a little looking through CVEs that mention ASN.1, it looks like the vast majority come from one specific ASN.1 parser, the one in OpenSSL, so it might just be that OpenSSL's code is a mess.

ff_• 12 years ago

This is the best feedback the author could receive: a violent but objective review of every weak spot. Well done.

runn1ng2• 12 years ago

The book actively recommends public key cryptography, because of concerns about key distribution. Again: bad strategy. Cryptographers use public key crypto only when absolutely required. Most settings for cryptography don't need it! Public key cryptography multiplies the number of things that can go wrong with your cryptosystem.

Can I ask why? What is so dangerous with asymmetric crypto compared to symmetric crypto?

mehrdada2• 12 years ago

There's one, admittedly theoretical difference, at least: there is such a thing as perfectly (information theoretically) secure symmetric encryption scheme (regardless of the computational power of the adversary), but asymmetric crypto, by definition, relies on being computationally infeasible, not information theoretically impossible.

Even though it's theoretical, the side effects of this fact surface from time to time as engineering issues in asymmetric crypto: all information that the attacker might need to break asymmetric crypto is more or less in the ciphertext, intuitively suggesting it's easier for asymmetric crypto to catastrophically go wrong.

runn1ng2• 12 years ago

No, I still don't get it. How is information about the private key in the ciphertext?

It's great that one-time pad exists, but it's not really relevant in actual crypto code, right?

The only actual reason I can think of is that symmetric crypto is easier to write and understand - you just mangle and xor some text back and forth, while in asymmetric crypto, you need to understand fairly complex algebra. But again, that's not that important if you use existing primitives, right?

a80002• 12 years ago

One symmetric cryptography method are one-time pads. Essentially you generate a truly random key (for example by observing some decay process) that has the same length as the maximum length of a message you might want to send and distribute the key to the receiver in advance. You encrypt the message by modular vector addition and decrypt it by subtracting the key. If you use the key only once and it is random, there can't be any attack on this method.

jimktrains2• 12 years ago

Possibly speed? Symmetric crypto is fast, and is often hardware accelerated. Asymetric is slow and not accelerated.

Not as big an issue with ECC, but RSA also has much larger block sizes, increasing the size of small payloads.

It's been my experience that Asymmetric is used for kex (key exchange) or key agreement or signing, but encryption is done using a symmetric algorithm.

yread• 12 years ago

But you would be using asymmetric only for exchanging keys for symmetric encryption.

tptacek30• 12 years ago

The biggest reason is that public-key crypto is "just a math problem" to an extent that isn't true of symmetric crypto. Diffie Hellman, for instance, is just an RNG and a couple modexps. There's no machinery of repeated substitutions and permutations and nonlinearities to hide your mistakes.

Another big reason is that public-key algorithms are parameterized to an extent symmetric systems aren't. Two random numbers is all you need to safely encrypt something with AES. Diffie Hellman, the simplest of the public key algorithms, needs a prime, a generator, and random private keys with particular relationships to those parameters.

jgrahamc• 12 years ago

I happen to know the author of this. This was a really tough thing for him to read, but he's taking it as constructive criticism.

I would add to the people commentating here on HN: tptacek's review is tough; you do not need to lay into the author of this book any more.

nailer• 12 years ago

It's a tough thing for anyone to read: it's browserWidth wide and monospaced.

Here's a readable version: https://gist.github.com/mikemaccana/10847077

andor• 12 years ago

it's browserWidth wide

I like that, because my browser window is resizable.

jacquesm4• 12 years ago

I think the tone is what makes it tougher than it needs to be, not the factual content. Props to the author for just looking at the content and not at the way in which it was delivered. Props to Thomas for taking the time to review the book.

znowi• 12 years ago

This condescending tone seems to be mandatory for karmic users of over 100K points :)

stavros• 12 years ago

You're being downvoted, but I agree that a greater amount of tact would have been warranted. Phrases like "I am not making this up", "argh!" and "huh?" add nothing to the review, but only serve to make it more personal, and I say this as a guy who also has very little tact.

VeejayRampay• 12 years ago

Well tell him that's a great reaction to have in that situation. I find it mature and I wish more people would act that way.

Jabbles• 12 years ago

It's unfortunate that it was too big for an HN comment, which would probably have prevented it being posted again as a topic. People who are genuinely interested in the book could have searched HN and found the original review. This thread just exists to bash/watch further bashing of the author/book.

shocks• 12 years ago

Agreed. I don't often flag submissions but I'll be flagging this one.

Most of us already read the review anyway.

dvanduzer2• 12 years ago

This is an incisive criticism, but it's extremely educational in its own right. I would not have read it otherwise.

When working through basic knowledge to mastery of a topic, attempting to teach someone else is an extremely effective way to organize your thoughts and learn yourself. This is why graduate students teach undergraduate students.

The author of the original book shouldn't feel shame for making the mistake of working toward mastery of the topic. But racing to publish is dangerous when the topic is as serious as (heart surgery or) cryptography. A stern warning is worth repeating.

mikeash10• 12 years ago

It's fortunate that it was posted again as a topic, as I didn't see the original comment thread and wouldn't have read this review otherwise, and I learned things from it.

rbanffy• 12 years ago

I have faith the next edition of the book will withstand tptacek's criticism much better.

conformal• 12 years ago

DISCLAIMER: i know and have worked with kyle (the author).

while the factual content of tptacek's review may be spot on, his overall tone is very negative and smacks of "only experts allowed" logic. while he could have easily helped improve kyle's book and shared these comments privately, he instead chose to lambast kyle publicly, which doesn't really help anybody: tptacek looks like a total jerk and kyle now has a lot of negative attention on (this version of) his book.

this pervasive "experts only" attitude is a big part of why "secure" open source projects have hard times getting and keeping contributors. it is par for the course for people to be super rude and negative to new participants instead of trying to encourage them to improve and learn. this lack of contributors then has a whole array of negative secondary effects, like less people reading the code for the project.

dvanduzer2• 12 years ago

Open source security projects have a hard time getting and keeping contributors because the expertise for this particular kind of work is difficult to develop.

Publishing a book like this sends a strong public signal of deep expertise.

I have not found tptacek to be overly rude or negative when offering advice to journeyman cryptologists. But a journeyperson should not necessarily be publicizing their how-to guides yet.

nuser• 12 years ago

I firmly believe that you shouldn't author a book in something if you lack the appropriate expertise. If you do so, you risk disseminating misinformation at scale, causing enormous harm.

Sometimes expertise is actually required.

ominous_prime2• 12 years ago

I understand where you're coming from, but the author is the one who put this out in public. Publishing a book like this sends a strong message of "I am an expert, take what is written here as fact".

Maybe the tone could have been a little softer, but this should not have been done privately. The criticism of the work needs to be just as public as the work itself, so that people who might have been misled have a chance to see why.

MattRogish2• 12 years ago

The "experts only" attitude is because, well, as we've seen with HeartBleed, this is VerySeriousStuff.

If the author instead put together a book on how a layperson could perform open-heart surgery, you're damn right that actual surgeons would jump all over it.

There is some strange pervasive attitude/arrogance in tech that all it takes to be good at something is to be smart and give it a try. Why learn the theory/fundamentals when you can just start coding?

For building a web app, sure. But security is not one of those things. You actually need to learn the fundamentals and theory, and even then, need lots of experience.

mikeash10• 12 years ago

Publicly discussing the flaws of a technical book actually helps a lot of people. I don't understand how it could possibly be better to have kept these comments private. By making them public, there are people who would have taken this bad advice who now know that it's bad advice. That makes us all more secure.

I really truly cannot understand the critique of an "experts only" attitude when it comes to technical books that make important recommendations for building critical systems. By all means, non-experts should experiment and build and learn. But non-experts definitely should not be giving out large quantities of advice in an authoritative tone.

mathattack2• 12 years ago

If you're writing a book on a serious topic like security, you are presenting yourself as an expert and need to be able to stand up to the criticism. It goes with the territory.

philh2• 12 years ago

he instead chose to lambast kyle publicly, which doesn't really help anybody

It helps people who might have read the book and learned to do things the wrong way.

We can model this as "Kyle has disseminated harmful material, and tptacek is trying to contain the damage". Kyle's feelings, intentions, and hard work aren't irrelevant; but they're not what we should be focusing on.

JunkDNA• 12 years ago

I'm sure the author is a nice guy. It is hard to put yourself out there like he has done. That said, when you put your name on something and put it in the public space, you have to be prepared for people to write these kinds of things. Furthermore, I think tptacek's blunt and at times snarky style is necessary to make his point. It is extremely hard to write clear critiques that don't sound harsh while at the same time clearly conveying the gravity of the situation. In short, tptacek can't afford the risk that softening his natural style means a major point will be missed. It's a bit like the old quote, "Sorry this letter is so long, I didn't have the time to make it short.". Politeness is a luxury one can't really afford when a book that has factual errors is already out there (and to be clear, I'm not qualified to assess whether this is true, I'm just speaking about the approach here). It is far better to write precisely what you're really thinking, than to couch it in all sorts equivocation and self-censorship.

Academic researchers get these kinds of critiques of their publications all the time. It's extremely useful to the whole academic process despite being infuriating and depressing. That said, most of those critiques happen before publication and in private. But as a book author, that's something one can control. If I were writing a book like this, my #1 worry would be that I was making claims or errors that would be held up on HN by folks like tptacek as evidence of my incompetence. I would therefore made it the highest priority to approach the most likely people to have an opinion to get them to review my draft ahead of publication. That's what people writing serious publications that have real world consequences do. Make no mistake: crypto is in this category. It's not like writing "The 4-hour Work Week", "Web Design for Programmers", or "JavaScript for Aspiring Ninjas".

raverbashing5• 12 years ago

"this pervasive "experts only" attitude is a big part of why "secure" open source projects have hard times getting and keeping contributors. "

Exactly

Not to mention the need to have to filter through all the BS criticism. I've read people arguing that there was no issue in having the e in RSA (the public exponent) equals to 1. Really.

tptacek30• 12 years ago

It's good to stick up for people. It's less good to be thin-skinned on someone else's behalf.

Here, your attitude causes two problems.

First, you know and apparently like Kyle Isom, and so I presume you're also ready to tell me that he's an adult and a professional. Professionals do one of three things with criticism: ignore it, rebut it, or learn from it. My assumption has been that Kyle is choosing options (1) and (3) from that list. But here you are, inventing option (4): "get indignant about it". I wonder if you've thought about the extent to which people will attribute that response not to you, but to Isom.

Second, whatever you might think about the tone of my feedback, it's clear that Isom needs additional technical review for his book. Whipping up a totally unproductive us-versus-them narrative about "jerks" versus "open source" does the opposite: it generates drama. Even if you think my review was itself dramatic, piling more drama on doesn't make Isom's work more attractive to experts.

I'm not sure how big of a deal either of these issues are, but they're a bad habit for message board denizens. The exact same thing happened to Willem when he wrote his critique of the Akamai allocator, and Hacker News had a totally unproductive drama storm for a couple hours before Akamai (a) thanked Willem and (b) acknowledged that he was absolutely correct. Read the Akamai comments on the HN thread, and apply them here, substituting "Kyle Isom" for "Akamai", and I think you'll see that they apply.

Finally, I'll admit to being personally irritated by the claim that I operate from "experts only" logic with regards to cryptography. There are at last count something like twelve thousand people who have reached out to us for our free crypto challenges, and thousands of those people have gone on to solve multiple sets of challenges (something like 60 people have finished the first 6). Every damn one of those people is an email exchange that me, Sean, or Marcin had to have directly, on our own time, with no compensation --- the opposite of compensation, in fact, because we donate to charity when people finish them.

There are a lot of people on the Internet to whom you could direct the "experts only elitism" criticism regarding crypto. I am not one of them.

What's more annoying about that bogus critique is how it muddles a real issue. I'd like many more people to understand crypto and, particularly, what goes wrong when it's implemented naively. But I'd like far fewer people to plow ahead and implement their own broken stuff. The track record on amateur cryptography is bad, and what developers don't like to acknowledge is that the badness that work generates is an externality to them. People have in the real world been hurt, physically, because of broken amateur crypto. It is hard for me to take the hurt feelings of developers all that seriously by comparison.

mbrameld• 12 years ago

Your assertion that tptacek's review doesn't really help anybody is patently false. It helped me by preventing me from making the mistake of purchasing this book.

0xdeadbeefbabe2• 12 years ago

How many books has he authored? This is very valuable data, and he stands to make an even better book even if all he does is change diffie hellman to appease tptacek and perhaps other readers.

nichochar• 12 years ago

I don't think he liked the book

mac1175• 12 years ago

After reading this, could anyone recommend a good intro to crypto book? I see a lot of good reviews of Bruce Schneier's Applied Cryptography.

scintill76• 12 years ago

Apparently the same reviewer says it's worse[0], unless he's talking about a different book. This surprises me based on Schneier's popularity, but having not read the book and not being an expert on crypto, I wouldn't know.

[0] https://news.ycombinator.com/item?id=7597970

floatboth• 12 years ago

"S->C nonce, C->S HASH(pw, nonce), HEAD->DESK smash" :D

raverbashing5• 12 years ago

Those with glass ceilings shouldn't throw stones

While criticism is good, the condescending way it is presented, as well as being overly critical are bad. Example:

"Total undue reverence for NIST and FIPS standards; for instance, the book recommends PBKDF2 over bcrypt and scrypt (amusingly: the book actually recommends against scrypt, which is too new for it) because it's standardized."

I know people love scrypt and bcrypt, and have been proven safe so far, but there are advantages to use standardized methods. An implementation can make something less safe than the standard.

tptacek30• 12 years ago

This is silly. There is no advantage to using PBKDF2 other than to placate PHBs. PBKDF2 (as commonly implemented, with HMAC-SHA2) is faster than bcrypt and scrypt and particularly straightforward to implement in GPU crackers.

bcrypt is also approximately the same age as PBKDF2.

And, finally, standardization is a very poor substitute for security analysis. PKCS1v1.5 is also a standard. If you want to argue against bcrypt, you'll have to marshal actual arguments.

raverbashing5• 12 years ago

I'm not arguing against bcrypt/scrypt per se.

I'm arguing that there may be advantages in using standardized methods (for interoperability) and especially implementations.

Which one is safer, using PBKDF2 from a known implementation or the "bcrypt library" for Ruby/Node that someone just posted to github? Oh what do you mean that's not how you read secure random numbers?

nkozyra4• 12 years ago

As someone finishing the final edits of a technical book (on Golang, at that) this is the kind of thing that horrifies me.

I want to go through every single chapter and rewrite it to stave off the imaginary critics in my head who will undoubtedly tear it apart.

karmajunkie3• 12 years ago

Friendly advice, find a few people you respect on the subject and ask them to review it. Wards off a lot of the anxiety and will generally make your work a lot better.

nkozyra4• 12 years ago

I'm sure that's great advice, but I don't respect anyone. :(

berdario2• 12 years ago

Can someone explain me this?

In considering RSA, the book recommends /dev/random, despite having previously advised readers to avoid /dev/random in favor of /dev/urandom. The book was right the first time.

From "man 4 urandom":

A read from the /dev/urandom device will not block waiting for more entropy. As a result, if there is not sufficient entropy in the entropy pool, the returned values are theoretically vulnerable to a cryptographic attack on the algorithms used by the driver.

In fact, using /dev/urandom is one of the causes of the creation of weak ssh key, found in this research: https://factorable.net/

So: Why is /dev/urandom the correct choice over /dev/random ?

natdempk• 12 years ago

Here's the blog post that always gets linked when this comes up: http://sockpuppet.org/blog/2014/02/25/safely-generate-random...

berdario2• 12 years ago

Thanks, I never read it before.

Anyhow, its conclusions seem to be mistaken to me:

It’s also a bug in the Linux kernel. But it’s also easily fixed in userland: at boot, seed urandom explicitly. Most Linux distributions have done this for a long time.

If you're an application developer (of something that runs very early in the boot process) but you're not making your own distro, and you can't trust your distro (I guess that since a lot of factorable keys existed, "Most Linux distributions have done this" might not actually hold true or count to a good enough percentage) you don't really have anything else that you can rely on to seed /dev/urandom explicitly

I'd think that the correct approach is to use urandom on everything but linux (after all, as long as your application isn't a blocker for the boot of the system, it doesn't seem terrible to wait for /dev/random)

Also, reading and blocking from /dev/random seems akin to failing early and explicitly (in the case where blocking on read is actually a problem), while reading urandom when not initialized seem to be a silent failure.

But I'm not going to write software that has to read from either device anytime soon, so don't panic if I'm mistaken :)

_delirium3• 12 years ago

Has anyone attempted to get any of these man pages (on any of the OSs) updated? I can't find any threads offhand of someone proposing a patch and having it rejected, but I haven't searched too diligently either.

solipsism• 12 years ago

I wonder who the intended audience of this review is. The book is clearly geared toward beginners. It would seem a review of such a book should be geared toward those who might read it to learn about cryptography. This review is obviously geared toward some other audience, however. Otherwise a criticism like The book writes its own Diffie-Hellman implementation and recommends it to readers would be backed up and explained, instead of being expected to stand on its own.

Is the audience for this review intended to be cryptography experts, who would not read such a book except to praise or trash it? If that's the case, it seems rather mean spirited. More "wow check this loser out" than "I don't recommend this book to beginners or anyone and here's why."

mti• 12 years ago

tptacek makes a number of good points but I find it hard to agree with this one:

there is concern that the NIST curves are backdoored and should be disfavored and replaced with Curve25519 and curves of similar construction.

Of course, "there is concern" is pretty vague, but it should be made clear that such concerns are in the realm of pure speculation at this point. There is simply no known way of constructing a "backdoored" elliptic curve of prime order over a prime field (in particular, the closest thing resembling such a backdoor, namely Teske's key escrow technique based on isogenies from GHS-weak curves, cannot work over a prime field). Scientifically speaking, I don't see more reasons to believe the assertion that "NIST parameters are backdoored because they aren't rigid" than the (equally unfounded) speculation that "Curve25519 may be weak because it has small parameters/a special base field/composite order/etc.".

Moreover, to say that the NSA has backdoored the NIST curve parameters is to assume that they have known, for quite a long time now, a serious weakness affecting a significant fraction of all elliptic curves of prime order over a given base field that has so far escaped the scrutiny of all mathematicians and cryptographers not working for a TLA. Being leaps and bounds ahead of the academic community in an advanced, pure mathematical subject doesn't quite align with what we know about NSA capabilities.

Don't take this the wrong way: there are good reasons to favor Curve25519 and other implementation-friendly elliptic curves (namely, they are faster, and they are fewer ways of shooting yourself in the foot if you implement them), but "NIST curves are backdoored" is not a very serious one.

tptacek30• 12 years ago

I actually agree with most of this.

The issue with the NIST P- curves is that there's no good reason to trust them. And, for what it's worth, being ahead of academia on pure math isn't science fiction; NSA employs a lot of mathematicians. But the notion of a backdoor in the NIST curves is totally speculative.

Here's what I was trying to capture:

http://www.hyperelliptic.org/tanja/vortraege/20130531.pdf

Despite its very weird submission as a story to HN, what you'd been reading was just a very long HN comment; I wrote it in a single draft and in the style I would use when writing a comment.

pbsd• 12 years ago

For the sake of historical accuracy, the NIST backdoor argument goes back to 1999 and Michael Scott [1]. I don't really buy it: if the NIST curves can't be trusted purely by association, then I find it very hard to trust the other curves as well.

[1] https://groups.google.com/forum/#!msg/sci.crypt/mFMukSsORmI/...

mikeash10• 12 years ago

After I finished reading this review, I came to check out the HN comments knowing that the tone would be the subject of the top comments.

When did this community become more concerned with tone than correctness? The top of this thread is filled with people saying that the tone is bad, it's unproductive, it's unnecessary, etc. Yet nobody seems concerned about the published book filled with bad information that a lot of people are going to "learn" from. What gives?

m0a0t0• 12 years ago

Perhaps the reason people are not commenting on the correctness as much is that it is, broadly, correct. It's quite difficult to add to a discussion when it's already right - there's no debate to be had.

mikeash10• 12 years ago

In which case, in a sane technical community, I would expect this thread to contain few comments.

mindslight• 12 years ago

The tech "community" (if you can even call it that anymore) has jumped a fucking pyramid of sharks.

Being right used to be the ultimate trump over social dynamics, which is what made tech a breath of fresh air to so many. Now that the field has become socially popular, it's been mired in the same vapid talking heads as everywhere else. And the people who actually know things are much quieter, as they generally have better things to do than compete for airtime.

_delirium3• 12 years ago

When did this community become more concerned with tone than correctness?

There's been a pretty strong concern about tone on HN from the early days, mainly (afaict) driven by Paul Graham having an interest in and repeatedly commenting about it. It's not the only concern, but avoidance of flaming and mean-spirited comments, in addition to avoidance of vapid or dumb comments, is one of the openly and repeatedly stated design goals of the community. I.e. it should be intelligent discussion, conducted in a collegial tone.

(This is a general comment on whether tone is and/or should be important on HN, not an evaluation of tptacek's review or implication that this comment/gist in particular would fall afoul of the intended HN standards.)

mikeash10• 12 years ago

I have no problem with that. Avoiding flame wars is a noble goal.

The problem I have is that people are freaking out over extremely minor matter of tone while ignoring important technical problems. Worrying about tone is fine. Worrying about it to such an extreme degree in preference to other things is not.

tptacek30• 12 years ago

If I had written a book on implementing cryptography in Golang, I assure you that someone else would have reviewed it harshly too. It's simply a difficult subject to get right.

jvehent• 12 years ago

It's not specific to cryptography. There is a hierarchy in all fields:

1. Top researchers come up with algorithms and techniques

  - The research corpus reviews them

2. Top programmers implements these techniques

  - The programmers communities review them

3. Top engineers write books to explain these techniques

  - which everybody else relies on in their tools

1 knows more than 2 which knows more than 3. But each group needs the two others, and the rest of the worlds needs all of them. People who write books are rarely the same people who come up with cryptographic breakthrough. Instead, they are engineers, and they can use a bit of help to get things right.

Your review was harsh, because you know more. What, I think, was missing from it is a bit of "This is a great first step, let me help you make it better so we can move everybody else forward. Here are my comments."

MattRogish2• 12 years ago

When you see someone repeatedly walking up the down escalator you don't give them an attaboy when they reach the top. You tell them to use the right escalator.

Varcht• 12 years ago

How can publishing a book purporting to be the way to do security be considered a first step? A first step would be to get some feed back from experts prior to publishing. This is the real world where this information is critical to our future, not something to be taken lightly. On a human level I have some sympathy for the writer but professionally I think Tptacek's response is completely acceptable and am glad I read it.

mathattack2• 12 years ago

Perhaps blogs are better for testing ideas than books?

sillysaurus32• 12 years ago

If I had written a book on implementing cryptography

I've been throwing $20 bills at my monitor so that your book will start downloading, but it doesn't seem to be working.

But really, you should write one.

tptacek30• 12 years ago

No, I'm not even close to qualified to write that book.

MetaCosm• 12 years ago

Most of your review seemed to be utilitarian and useful for a second edition. That is awesome, the way you structured it means the author could use a ton of it, and it gives readers specific things to be aware of. Sincere thanks for that.

That said, you first point seemed silly. Simplified, partial and building block examples are used in almost all fields to facilitate teaching (including among medical students and surgeons). They are useful because they keep people moving along the process, teaching them terms, skills and concepts they will need to get to the next step in the process.

What is your alternative method for teaching someone unfamiliar with these concepts in a way that won't just put them out to sea without a paddle?

tptacek30• 12 years ago

The author doesn't demand that his readers implement AES or SHA2 directly. So, what I would do is start with a simple, secure design based on an AEAD like AES-GCM, which is also in the Golang standard library. I would accompany that design with very strong warnings that substituting AES-GCM for anything else is likely to destroy the security of the design. Then, when I wanted to teach about generically composed MACs, my HMAC example would involve replacing AES-GCM with AES-CTR+HMAC. At no point in the book would the focus of one of my chapters be a design that was dreadfully insecure.

I would also divide the book into two parts, the "easy" part and the "hard" part. The "easy" part would get readers to the point where they can safely use TLS, reliably PGP-encrypt something, hash a password, and invoke NaCl (which is part of the go.crypto package). I would probably spend a whole chapter on how to use Golang's TLS library, for instance. Most readers that are picking the book up so they can solve some business problem would probably never need to get past the "easy" part, and I would encourage them not to.

I would remove from the "hard" half of the book protocols that were insecure. An unauthenticated DH exchange is a poor basis for a cryptographic transport. Slash, cut, gone. A naive password challenge-response protocol doesn't solve anyone's business problems. Slice, snip, gone. In their place, I'd probably add more discussion of key exchange algorithms, with particular attention paid to how easy they are to get wrong.

archgoon• 12 years ago

While reading your review, one of the main criticisms seems to be that the it's not made sufficiently clear that the code as written is insecure.

In keeping with the philosophy of being hands on; would the book be improved if after introducing the code in the first section, have the reader implement an exploit for the same code?

tptacek30• 12 years ago

I feel comfortable with the idea of writing a book showing people how to break badly-implemented crypto designs, so much so that Sean, Alex, and I are in fact writing that book; it'll be a "pay-what-you-want" directly to a preferred charity. If anyone can point us to someone who will take our money to expertly typeset a giant text file, that would be helpful.

I do not feel remotely comfortable with the idea of writing a book containing prescriptions on how to design a cryptosystem. We're wary of doing that even for our clients, where we know all of the context and the threat model that the proposed system would face, and who will actually build it, and that we'll get paid to review the resulting implementation. I don't know how to solve that problem for strangers.

Other people do. They are much better than I am. When Trevor and Moxie write the book on why they chose the TextSecure primitives that they chose, I'll be first in line to buy.

pronoiac• 12 years ago

Reading this makes me think that the Go crypto primitives could use a lot more plumbing; it would make them more useful, and avoid some pitfalls by making it easier to do the right thing.

tptacek30• 12 years ago

Strong agree. I like Go's crypto library, but wish it had higher-level interfaces.

feralchimp• 12 years ago

This is a great review for two reasons:

a) it provides readers with a laundry list of things to go study independently

b) the book author can, given time and inclination, do the same study and improve the book

uuid_to_string• 12 years ago

The author is a systems engineer at Cloudflare.

Tptacek's Review of "Practical Cryptography With Go"

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