4 ms·
Break Me If You Can: Exploiting PKO and Relay Attacks in 3DES/AES NFC
- 1970-01-01 8mo ago3DES has been broken for a decade. Nice job putting it all together though.
- tptacek 8mo agoIt has? What exactly do you mean by that?
- zxcvasd 8mo agoif i were to guess, they are referring to CVE-2016-2183, which lead to deprecation of 3DES by NIST in 2019 (announced in 2017) and disallowing all uses in 2023. openssl also stopped including it in default builds starting in 2016 because it is considered weak.
- tptacek 8mo agoThis is Sweet32, an attack on any block cipher with an 8-byte block size. We don't consider those ciphers "broken"; they just can't be used safely in some common modes. You shouldn't use 3DES or IDEA or Blowfish, of course, but I don't think they're considered "broken", not in the same sense that, say, RC4 is.
- zxcvasd 8mo agoto any non-cryptographer, i think that's a distinction without a difference. it's disallowed from use by the major standards institute due to a vulnerability where people can recover the plain text. that sounds "broken" to me, but i'm not a cryptographer. so, i'll defer to you when you say it's not broken. (i dont know what the cryptographer-specific definition of broken is -- it'd be great if you would shed some light on that)
- tialaramex 8mo agoIt's true that 64 bits was known not to be enough when DES shipped decades ago, but there is some difference between "We know that's a bad idea" and a demo showing why, and so I think I'm OK with the word "broken" in that context. There's a reason POCs matter right? Why you feel comfortable (even though I don't agree) saying multi-threaded Go doesn't have a memory safety problem and yet you wouldn't feel comfortable making the same claim for C++.
- fc417fc802 8mo agoI'm not a cryptographer but to me "broken" seems to imply that the core algorithm itself can be attacked. If merely applying it in certain ways as part of some larger system can fail then aren't most (possibly all) ciphers broken? It's entirely possible to do all sorts of stupid things. Granted, a 2^32 block limit is pretty severe by modern standards.
- upofadown 8mo agoSi (2^32)*8 works out to 34GB for TDES. How many applications involve encrypting that much data in one go?
- fc417fc802 8mo agoSorry, calling that a block limit was an error by omission on my part. 2^32 yields a 50% chance of reuse. If we pick a sane security margin it's a lot smaller. Assuming I did the math correctly just now, 2^-32 only gives you ~2^17 blocks; dropping that to 2^-24 yields ~2^21 blocks.
- upofadown 8mo agoOff the top of my head, NIST was suggesting something like 8GB as the working limit. It would depend on your risk tolerance and the application in practice I guess. For something like video you might not really care about exposing a few 8 byte blocks here and there where the exposure is one block XORed with the other.
- _tk_ 8mo agoNot to be rude, but it seems to me that you are engaging in some hairsplitting. In general, security people do not recommend to use 3DES or RC4 - even if RC4 is broken in other ways than 3DES.
- tptacek 8mo agoRC4 is actually broken. It's fundamentally broken. As you run it, it's face melts off like the guy at the end of Raiders. It's genuinely weird nobody noticed how bad it was, in a practical sense, until the late aughts. The 64 bit block size in 3DES (and Blowfish and IDEA) limits how much data you can encrypt under a single key. I think the real "tell" that this isn't hair-splitting is that people don't ever generally talk about Blowfish being "broken", just obsoleted.
- 1970-01-01 8mo agoIt means you should not use it for anything important, because it can be decrypted by the public with little effort. If you look back, it has been this way for quite awhile. My gripe is with the clickbait title 'Break Me If You Can' https://nvd.nist.gov/vuln/detail/cve-2016-2183 https://nvd.nist.gov/vuln/detail/cve-2016-2183
- tptacek 8mo agoHow exactly would you decrypt a 3DES ciphertext "with little effort"?
- 1970-01-01 8mo agoIt's supported in hashcat
- some_furry 8mo agoIs this a bit?
- 1970-01-01 8mo agoHave you tried it?
- some_furry 8mo agoWe're talking about symmetric ciphers and you're talking about password cracking software. Triple-DES has 168 bit keys. Even if you use a meet-in-the-middle attack, your attack cost has an exponent of 112 (with an associated memory cost with an exponent of 88). That's not practically exploitable today. If you think I'm wrong, here's a single block message encrypted with 3DES, then hex-encoded. Have fun: 924db449f52ea976 But really, the bigger problem is Sweet32.
- tostrstrudel 8mo agoBREAKMEIFYOUCAN! is the default factory key programmed into every MIFARE Ultralight C chip by NXP.
- gjurhgd 8mo agoSurely someone who has been here as long as you have understands that this type of behavior is not compatible with the guidelines. > Converse curiously; don't cross-examine. You could have just corrected them and not goaded them into further revealing their ignorance. Yes, they underestimated how difficult it is to crack 3DES. You could have simply told them that.
- tptacek 8mo agoI have no idea who they are or what they were talking about. I think they're thinking about 3DES used as a password hash. I never in 100 years would have guessed that's where they were coming from. The thread that ensued, a discussion of what it means for a cipher to be obsoleted or unsafe versus "broken", is an actually-interesting question. I feel pretty OK about how this went.
- gjurhgd 8mo agoYou could never, in a million years, have guessed by "broken" they meant "it can be decrypted by the public with little effort?" I doubt that. I see no evidence they are talking about a password hash. Here's what they actually cited: > The DES and Triple DES ciphers, as used in the TLS, SSH, and IPSec protocols and other protocols and products, ... They're clearly talking about it's use as a cipher. Again, someone who has been here as long as you have should understand that you shouldn't put words in their mouth or be evasive in this way. The conversation would still have touched on these interesting topics, and would likely have done so more immediately.
- tptacek 8mo agoDo we have conflicting premises about what Hashcat is? I'm pretty sure you're just wrong here.
- gjurhgd 8mo agoDo we have conflicting premises about what SSH is? I'm pretty sure you're dodging and deflecting from the actual issues here. They were clearly suggesting that there exists a publicly available tool to attack this algorithm. They clearly didn't care one way or the other about whether it was used in passwords. What they actually cited was vulnerabilities in network services. You are being disingenuous. Cut it out.
- moribvndvs 8mo ago> Is this a flaw in the cryptography itself? No. The underlying cryptographic algorithms (3DES and AES-128) remain secure. The vulnerabilities arise from: Protocol design choices that allow unauthenticated memory writes after initial authentication Lack of atomicity when writing cryptographic keys across multiple memory pages Widespread misconfiguration in real-world deployments (unlocked memory, static keys) Non-NXP compatible chips with severely flawed random number generators
- arkwin 8mo agoLooks awesome! I see some Flipper Zero apps were already created. When will you be releasing this for the Chameleon? Also, any plans to port this over to the Proxmark?
- noproto 8mo agoAll of the attacks are released for the three platforms (Proxmark3, Flipper Zero, and Chameleon Ultra). Our goal was day 1 support for RFID testing devices.
- redbell 8mo ago> Break Me If You Can This, somehow, triggered my mind to recall LifeLock's CEO Todd Davis’s public marketing campaign where he displayed his Social Security number on the company website and advertisements to demonstrate the security of his platform, however, the challenge backfired dramatically and he becomes a victim of identity theft on at least 13 separate occasions.