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Comment by dr_hooo | Hacker News Reader

Hmm, I don't really see any really convincing points, or workable alternatives that your linked article provides.

Nevertheless I would like to read more about this claim:

> It [PGP] was designed in the 1990s, and in the 20 years since it became popular, cryptography has advanced in ways that PGP has not kept up with. So, for example, it recently turned out to be possible for eavesdroppers to decrypt messages without a key, simply by tampering with encrypted messages. Most technologists who work with PGP don’t understand it at a low enough level to see what’s wrong with it.

(I admit I am one of these technologists)

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My best guess is that they really meant EFAIL but didn't want to actually mention it because EFAIL had nothing to do with any weakness in the OpenPGP standard or the GnuPG implementation. Instead it was a HTML email horror story where someone figured out how to forward entire decrypted messages using image links.

So just more pointless anti-PGP innuendo...

That is not in fact a good description of EFail, which was indeed caused by a failure both of the PGP protocol and of GPG, its reference implementation.

>...a failure both of the PGP protocol ...

No. There were some changes in the actual protocol document that came out of EFAIL but no actual changes to the protocol other than a depreciation that was happening anyway.

>...and of GPG, ...

This also seems to be false. GPG didn't have to change anything as the result of EFAIL...

>...its reference implementation.

Also false. OpenPGP does not have a reference implementation.

There were no changes in TLS after Bleichenbacher '98; instead, implementations just incorporated increasingly hacky workarounds. The PGP post upthread details the problems with the MDC, and the compounding implementation flaw in GPG that released unauthenticated plaintext to callers.

That MDC-era PGP remains the global standard, and that GPG continues to release unauthenticated plaintext to callers, just calls out further the impossibly compromised position PGP-based cryptosystems are in. You can try to do things like Sequoia that modernize PGP, but nobody in the installed base will be compatible with you, and the most popular and important "driver" of the protocol (again, GPG) is disinterested in mitigating the flaws of legacy PGP.

You can choose not to call GPG the PGP reference implementation, and there's no formal declaration anywhere saying that, but, it obviously is.

It is odd you bring up MDC in the context of EFAIL as the EFAIL researchers were unable to come up with an exploit that MDC did not detect. Even if you feel that GPG should of anticipated EFAIL that means that OpenPGP as a protocol was secure against EFAIL.

It is entirely accurate to say that EFAIL in not applicable to OpenPGP. You might not like MDC but you have to admit that EFAIL is not an example of any sort of a weakness in MDC.

I feel like we're not reading the same paper. The EFail paper I'm reading has a prominent chart showing which implementations it was possible to break the MDC in, and a section detailing how the MDC can be straightforwardly stripped off messages.

I note that you didn't respond to the rest of my comment.

Yeah, the paper did not claim that the MDC was in any sense "stripped off messages". They instead claimed that the mail clients ignored the MDC error.

>I note that you didn't respond to the rest of my comment.

The TLS stuff? We are just quibbling here. You have an irrational hate of things called PGP. Nothing I can say is going to change that.

Added: You are the one that brought up the MDC stuff but that really is beside the point. The problem here is with the leakage that HTML emails allow. EFAIL would still have nothing to do with PGP even if MDC did not exist.

Search the Enigmail forums for people who couldn't open their emails after GnuPG made MDCs mandatory (as a reaction of Efail). Especially people with old PGP keys were receiving non-MDC (SE) ciphertexts since ever. Mozilla's bugzilla (and a bank I heart of) were using non-MDC encryption. Reading the OpenPGP RFC, this is perfectly fine behaviour.

The Efail paper also describes a way to downgrade MDC ciphertexts to SE ciphertexts. This was known since 2015, but not addressed in OpenPGP.

So OpenPGP according to RFC 4880 allows SE packets with no MDC, and the MDC can be stripped away in a standard conforming way (tho with some guessing of bytes). If that isn't a problem with the OpenPGP standard, I don't know what is.

Just weeks after Efail, they made SE packets (those with no MDC) deprecated in the current RFC 4880bis. They were careful to not mention Efail, because it wasn't OpenPGP's fault. For some, it's never OpenPGP's fault.

Interesting. I was not aware of this particular issue. Is this it?

* https://dev.gnupg.org/T3981

As mentioned in the discussion:

>Actually this is not related to the mentioned CVE because the issue we are talking about has not been tested by them.

So it appears that the EFAIL people could of prevented MDC from thwarting their attack if they had used a really old cypher. So, OK I will concede that EFAIL at least inspired a change in GPG. My original statement that GPG required no changes as a result of EFAIL is still correct as stated though.

We are still quibbling here. I don't think that S/MIME was deficient in any way with respect to EFAIL either. So all this discussion about MDC is still pointless to me.

It is talking about things like efail.

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