Skiff: Various Privacy Failures

Skiff: Various Privacy Failures(grepular.com)

60 points by uselpa 2 years ago | 25 comments

cedws 2 years ago |

I see Skiff also advertises itself as "end-to-end" encrypted. This is the same misleading advertising as ProtonMail is guilty of. Traditional email cannot be E2E encrypted because of protocol limitations. You can technically achieve E2E encryption if using PGP, but if the private keys are not in your control then it is effectively pointless.

ProtonMail can only guarantee E2E encryption without PGP if you are sending email to another ProtonMail user. I don't know if Skiff also offers this special kind of encryption. Either way, they should be more upfront about the level of privacy they can offer.

I had a read of Skiff's page on E2EE. It is very carefully worded and, from a skim read, is not upfront about the fact that un-PGP'd email sent and received through Skiff can be read by Skiff.

https://skiff.com/blog/end-to-end-encryption-email

Oh, one more thing. Skiff's SMTP server (inbound-smtp.skiff.com) is running on AWS in the United States which means it will be beholden to US warrants. Skiff does not have a warrant canary. Getting big Crypto AG vibes from this.

mweidner 2 years ago | |

The product page is clearer (https://skiff.com/mail):

> All emails between Skiff users are end-to-end encrypted, including both subject and contents. External mail is encrypted with your keys on receipt, keeping it private.

Doxin 2 years ago | | |

That is however, quite specifically, not end-to-end encryption. The whole entire point of end-to-end encryption is that no intermediary gets to see the unencrypted content.

protonmail 2 years ago | |

Regarding Proton Mail's encryption: Proton's servers don't hold your private key directly — it is generated client-side and stored encrypted with your password. You can also import your own keys: https://proton.me/support/pgp-key-management. That way, you can stay in full control of your keys.

Additionally, Proton Mail uses OpenPGP internally, so Proton-to-Proton messages are always protected by PGP. Even for external messages, contacts don't necessarily have to set up PGP encryption manually; the email client can do so, enabling the use of end-to-end encryption between different providers with minimal hassle.

lcof 2 years ago |

Great read, I have seen this myself in the last 4-5 years with services surfing on the privacy wave - I mean, not just email, but also cloud drive. My conclusion, even regarding established privacy-focused email providers, is that it’s not worth the hassle, really. I use trusted and reliable email providers (according to me), and I just don’t use email for anything sensitive. That’s just right for me.

I know some people do need more privacy and/or security. But a lot of people think they need the same but really, they don’t.

forwardemail 2 years ago |

Forward Email team here (https://forwardemail.net), we have a write-up and comparison @ https://forwardemail.net/en/blog/docs/best-quantum-safe-encr...

We've considered adding a E2EE comparison column as well (with the issues such as Proton rewriting your emails @ http://jfloren.net/b/2023/7/7/0 highlighted).

Privacy Guides Discussion @ https://discuss.privacyguides.net/t/forward-email-email-prov...

Unlike Skiff, Proton, and Tuta... we're _actually_ 100% open-source. Those providers that advertise as open-source really only open-source the front-end, when the back-end is the most sensitive part of an email service.

crimbles 2 years ago |

Interesting read. I will point out that having seen "security audits" done by top tier well known security companies, they aren't worth the paper they are written on. They are selling you a pen test script run, the output of which is farted into a document for the least amount of time they can expend on it.

If you want security, you have to do it in house with competent people who understand your business domain. So when I see people with regular pen tests I know they don't really give a shit because they are doing minimal ass coverage.

mratsim 2 years ago | |

Disagree, their reputation is tied to their audit quality.

But I'm pretty sure in this case the scope was bad. Like they coukd have had audits on "Do I use OpenSSL well?" and then misrepresent that all their privacy claims were audited.

Now it seems like Skiff conveniently didn't allow Trail of Bits to publish their reports, they are usually here: https://github.com/trailofbits/publications/tree/master/revi...

Disclaimer, I have used Trail of Bits service in the past (and 2 other auditors for an security campaign on a blockchain, cryptography + networking product).

jitl 2 years ago | |

Really? That’s not my experience. I’m not denying companies are out there basically selling a rubber stamp like you say, but I’ve worked with sharp folks from Matasano and NCC Group who would go deep, learn from eng about system but also do blind red teaming, do physical pen tests etc. I think you’ll probably get what you pay for and get good results if you put in good effort working with them.

I can’t speak to Cure53 but I feel like I’ve seen that name on a few failed cryptocurrency thingies.

crimbles 2 years ago | | |

I was actually including NCC in that one...