Beta
×

Welcome to the Slashdot Beta site -- learn more here. Use the link in the footer or click here to return to the Classic version of Slashdot.

Thank you!

Before you choose to head back to the Classic look of the site, we'd appreciate it if you share your thoughts on the Beta; your feedback is what drives our ongoing development.

Beta is different and we value you taking the time to try it out. Please take a look at the changes we've made in Beta and  learn more about it. Thanks for reading, and for making the site better!

Comments

top

eBay Compromised

mattpalmer1086 Re:Would be 100 million as fast as hashcat claims (193 comments)

Hmmm... I got my performance stats from a different web site. But the performance table on oclHashcat's fron page says 11231M c/s for SHA256. That's eleven billion a second, admittedly using 8 GPUs, but in the ballpark of my original post.

If crypt is iterating SHA256 110,000 times, that sounds fairly good. I've been looking at scrypt, which is explicitly designed to resist hardware based attacks.

about 4 months ago
top

eBay Compromised

mattpalmer1086 Re:3,963 years per password (193 comments)

Well, I would dispute those calculations a bit, but I accept that good long per-account salting forces each password to be cracked individually. I assume that the salt is compromised along with the password (or they won't be cracked at all).

Even randomly selected passwords from all alphanumeric characters only gives us about 6 bits of entropy per character. Most passwords are shorter than 10 characters, the average is more like 7. This only gives us 42 bits of entropy per password, assuming complete random selection from that space.

But - users don't randomly select from that space, and modern password crackers don't simply try all possible letter permutations, although they can successfully do this for passwords which are less than 7 characters. They exploit the patterns and techniques which users use to select passwords, using rules engines, password dictionaries, markov chains and all sorts of clever magic.

Run this on GPUs using hashcat, which for SHA256 can check about 3 billion hashes a second. A small cluster of 4 of these machines can then easily check over 10 billion hashes a second. You can now rent Amazon EC2 instances with GPUs. In a minute you can check 600 billion hashes, admittedly for a single password at a time.

Salted hashes are now crackable even for quite reasonable passwords, if the hash algorithm can be run on modern GPUs, and assuming the attacker has the salt as well.

about 4 months ago
top

eBay Compromised

mattpalmer1086 Re:Hash algorithm? Static salt like eBay Japan? (193 comments)

It's not particularly the strength of the hash that worries me, it's the speed of it. If they're using something like SHA256 - strong, but fast - then I'd be worried.

about 4 months ago
top

C++ and the STL 12 Years Later: What Do You Think Now?

mattpalmer1086 Re:Why use it? (435 comments)

Good point. I checked out http://www.stroustrup.com/appl... and I can see they're mostly all quite demanding applications. I guess they deserve a demanding language :) But yes, fair enough. There are plenty of times getting the most out of what you have is going to be important.

I once worked on Java code which ran on the most ludicrously limited hardware. It was like treacle. I spent a lot of time tuning that code. Logging was the worst offendor, but some poor algorithms lurked in there too. Garbage collection was quite noticeable, even after rewriting to minimise it as much as possible.

about 5 months ago
top

C++ and the STL 12 Years Later: What Do You Think Now?

mattpalmer1086 Re:Why use it? (435 comments)

Fair enough... I'm pretty ignorant on how CUDA or OpenCL is programmed. What is it about C++ that makes it a good fit?

about 5 months ago
top

C++ and the STL 12 Years Later: What Do You Think Now?

mattpalmer1086 Re:Computational code (435 comments)

Yes, I can see that sort of code would benefit a lot. Not an area I've done much work in, but I guess a lot of people are. I'm actually really interested in code that performs well - I spend quite a lot of time profiling and tuning. Some of the things Martin Thomson has done in Java land are pretty cool. Check out http://lmax-exchange.github.io... and http://mechanical-sympathy.blo...

about 5 months ago
top

C++ and the STL 12 Years Later: What Do You Think Now?

mattpalmer1086 Re:Why use it? (435 comments)

Sure, resource handling in C++ is one of the examples I do give of the sheer power and beauty of what you can do with the language. I used it extensively even back then. I also remember some of the issues I encountered in passing them around safely were a big lesson in the complexities, pitfalls (and opportunities) that lurk in the language. It was enormous fun, but I think I've probably been more effective in less demanding languages.

about 5 months ago
top

C++ and the STL 12 Years Later: What Do You Think Now?

mattpalmer1086 Why use it? (435 comments)

I had the most fun ever with C++ back when the original story ran. But it was too complex, too big and yet lacking standard ways of doing really very common things. Every library took a different approach. No standard libraries to do pretty much anything you wanted to in the real world. And it was always possible to shoot both feet off at once while doing something you thought was obvious and/or designed to make your code safer. Incredibly slow to compile. Compilers never supported the full C++ spec, or supported different bits of it on different platforms.

The trouble is, I can't see any compelling reason to use it for anything much these days. Maybe the latest C++ is better - but given what I know of the language I suspect the main criticisms I have of it must be still valid.

Use cases where you need that insane low level of power and control while retaining a high level language syntax are not common at all.

Can anyone give an example of where C++ really shines these days over other languages?

about 5 months ago
top

NYU Group Says Its Scheme Makes Cracking Individual Passwords Impossible

mattpalmer1086 Re:Is this different than a "secret salt"? (277 comments)

It looks like a message authentication code, but it isn't. Hash(Key || data) is vulnerable to a length extension attack.

about 5 months ago
top

NYU Group Says Its Scheme Makes Cracking Individual Passwords Impossible

mattpalmer1086 Re:really? (277 comments)

I think we need a "Misleading" category.

Without the salts, the hashes are essentially uncrackable, if the salts aren't incredibly short. So don't waste your time trying to crack these.

Salts are not secrets. They are usually stored right alongside the account details in the password database.

If your solution is to make the salt secret, you're not using salts anymore. Per-account salts protect against pre-computation attacks and do not need to remain secret to provide this protection. They are a cheap and effective defense for this purpose.

If you want to keep your salts secret, they are technically called "keys", and are expensive and difficult to manage securely.

about 5 months ago
top

Is Whitelisting the Answer To the Rise In Data Breaches?

mattpalmer1086 Re:We're adopting this at work... (195 comments)

The software running on the POS is completely known and controlled. In a big organisation there are lots of them, so you want to be able to update over the network. Updates are tested and bundled with any whitelist updates required. It's the perfect environment for whitelisting.

I'm curious why think it won't work on a POS with remote updates?

about 7 months ago
top

It's Not Just the NSA: Police Are Tracking Your Car

mattpalmer1086 Early Warning (201 comments)

I attended a conference on XML back in roughly 2004. A police technical architect was describing the ANPR system. He pointed out that the current deployments of the time were entirely local and not joined up nationally - but went on to say that it wasn't a very big step to do this, allowing the tracking of vehicle movements on a national scale. He looked embarrassed and uncomfortable as he said this.

I got the very strong impression at the time that he was trying to give a warning on where this technology was heading.

about 8 months ago
top

IETF To Change TLS Implementation In Applications

mattpalmer1086 Re:We did it wrong, let's do it wronger still. (80 comments)

I'm no expert on id-based encryption, although I can just about understand how it works. It has some attractive properties as well as some serious downsides.

Pros:
  * An encryptor can pick a public key at random for a recipient known to the decrypting authority.
  * No prior arrangement is required except for knowledge of the public parameters of the authority, and a recipient to send a message to.

Cons:
  * The private key of the recipient can be calculated at any time by the decrypting authority.
  * The recipient must authenticate to the decrypting authority to receive the private key for the sender-chosen public key.
  * All messages in the past and in the future can always be decrypted by the decrypting authority at any time.
  * You have to trust this authority absolutely.

The fact that the private key can be calculated from the public key and the master secrets is actually a pro as well as a con. This is what lets the sender choose a public key of their choosing with no prior arrangement.

I've seen this work quite well in one setting - payment messages from secure pin entry devices to the payment processor. In this case, the payment processor can decrypt all payment messages at any time, but each message is sent using a different key for each transaction, chosen by the low power pin entry device, and requiring no interaction between them and the processor.

On reflection, it's probably not a good candidate for inclusion into a protocol that would replace TLS. I can't really see how it provides anything useful in that setting. Still, it was just an example of some of the cool ideas being realised in more modern cryptography :)

about 9 months ago
top

IETF To Change TLS Implementation In Applications

mattpalmer1086 Re:We did it wrong, let's do it wronger still. (80 comments)

Well, I can't really make out what you're proposing here.

As far as I can see, the client side has three secrets to maintain - the GUID, master password and salt. If the GUID is unique to a computer, your accounts only work from a single machine, and if you lose the GUID then you lose access to all your accounts. Correct?

The nonce is a "number used once" - i.e. randomly generated for each session in a cryptographically sound way.... so how do the server and client negotiate the nonce for each session? Does one pick it and encrypt it to send to the other? Do they both participate in picking it? Do they use something like Diffie-Hellman to arrive at the value?

I really don't understand your point about changing the salt equals changing your logins without affecting your password. Do you mean if I wanted to lose access to all my accounts everywhere and begin again, I wouldn't have to change my password?

And... how do you know you're talking to the right server in the first place? I don't see any server authentication at all in your proposal.

That's enough for now. The one thing I've learned from studying protocols is that it's really, really hard to get right. Not because the people creating them are dumb or have malicious intent. It may well be time to start creating a new protocol to replace TLS eventually, using what we now know about trust, authenticated encryption, protecting the handshake and side channel attacks. And possibly using some new techniques in there, like identity-based encryption...

about 9 months ago
top

Group Thinks Anonymity Should Be Baked Into the Internet Itself Using Tor

mattpalmer1086 Re: I wonder how long (123 comments)

Go for it.

Don't worry - you won't get anywhere close, but I guarantee you will learn a lot.

Start by trying to define what you are protecting from whom, and how two arbitrary endpoints who have never met can know they are talking to each other and not a man in the middle.

about 10 months ago
top

Azerbaijan Election Results Released Before Voting Had Even Started

mattpalmer1086 Inefficiency is a feature (266 comments)

This is a really good point. The inefficiency of physical ballots requiring large numbers of people to participate is a security feature!

about a year ago
top

Stealthy Dopant-Level Hardware Trojans

mattpalmer1086 Re:BTW... (166 comments)

A belief in GW is entirely compatible with having a beach front house. The problem is that it is slow moving but inexorable.

Personally, I'm with the vast, vast majority of scientists who claim it's real and extremely dangerous. From what I've seen of the human race, we won't do anything until we get badly burned.

I guess everyone will know for sure one way or the other in a few decades. I just hope we can live with it.

1 year,6 days
top

Stealthy Dopant-Level Hardware Trojans

mattpalmer1086 Re:BTW... (166 comments)

I thought we already covered this in the linux rdrand story. It's called unauditable because it whitens the raw entropy output using encryption on chip, making even quite non-random source data appear to be random. It is not called unauditable because it's a black box design. The paper states that the design is very well known.

The attack described in this paper is to modify both the entropy source output "c" and the post-processing encryption key "K", undetectably setting a fraction of them to constant bit values. This weakens the effective random number generation to some chosen n bits of entropy, instead of 128 bits. But because the AES encryption post-processing stage does a very good job of making its output appear random, it will still pass random number tests.

If we had access to the raw entropy source, we could see that it was not providing nearly enough entropy to the encryption post-processing stage.

1 year,6 days
top

Ask Slashdot: Are 'Rock Star' Developers a Necessity?

mattpalmer1086 Re:Help them realize they're the asshole, with a b (356 comments)

Interesting. I once managed a very bright and young developer, whose coding was exceptional. He was very often (but not always) right. But he was also rude and completely lacking in any social graces. And it wasn't enough that he was right - he also made everyone else feel stupid and frustrated.

I had to find solo projects for him, as the rest of the team ended up flat out refusing to work with him - and I didn't blame them.

1 year,7 days

Submissions

mattpalmer1086 hasn't submitted any stories.

Journals

mattpalmer1086 has no journal entries.

Slashdot Login

Need an Account?

Forgot your password?

Submission Text Formatting Tips

We support a small subset of HTML, namely these tags:

  • b
  • i
  • p
  • br
  • a
  • ol
  • ul
  • li
  • dl
  • dt
  • dd
  • em
  • strong
  • tt
  • blockquote
  • div
  • quote
  • ecode

"ecode" can be used for code snippets, for example:

<ecode>    while(1) { do_something(); } </ecode>