Post B1Ev177hetTTGyJed6 by arcanechat@fosstodon.org
(DIR) More posts by arcanechat@fosstodon.org
(DIR) Post #B1Ev177hetTTGyJed6 by arcanechat@fosstodon.org
2025-12-14T09:39:00Z
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"Tool allows stealthy tracking of #Signal and #WhatsApp users through delivery receipts"https://cyberinsider.com/tool-allows-stealthy-tracking-of-signal-and-whatsapp-users-through-delivery-receipts/Another privacy vulnerability caused by the dependency on phone numbers. In #ArcaneChat (and other #chatmail clients like #DeltaChat) you don't need a phone number (or any private data at all!) to register, so such attacks are simply impossible, keep your family safe, join https://arcanechat.me
(DIR) Post #B1Ev180eMbQW1O1XH6 by david_chisnall@infosec.exchange
2025-12-14T10:09:27Z
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@arcanechat When you post something about a vulnerability in another messenger and completely misrepresent it, in a way that implies that you don’t understand the cause of it at all, it gives me no confidence in your system.The root cause is nothing to do with phone numbers. It depends on two things:Being able to send messages to someone from some public identifier. Any messenger that doesn’t require an interactive flow for pairing devices (as some military systems do) has this feature.Receiving read receipts from messages. Signal allows you to turn off read receipts if you are concerned about information leaks from them.If you actually wanted to convince people your system was better you would:Show that you don’t issue read receipts (which will put some people off because they are useful).Show how you mitigate this kind of attack, by rate limiting this kind of message, adding jitter to responses, and so on.Email-based flows tend to not be vulnerable to this kind of attack because they do most of the processing on the server, so you’d only be able to probe the server. But you wouldn’t bother because email has so little metadata protection that you don’t need to bother with an attack like this. From what I know of DeltaChat’s group chat protocol, I suspect there is a way of triggering a similar attack by sending broadcast invalid messages and timing the error response. If you really wanted to convince people that your system is better, you’d show a security analysis that explains why I’m wrong, rather than just say ‘I don’t understand this attacks but the researchers who published it didn’t bother trying to attack the protocol I use and so I’m sure it is secure!’ That is exactly the attitude to security that makes me distrust DeltaChat.Oh and before anyone jumps in with anything about XMPP: this attack is completely trivial on XMPP. Send an invalid iq stanza to the client’s bare JID and time the response. And this is impossible to fix without redesigning the protocol because unknown iq stanzas must be forwarded to the client to enable future extension and clients must respond with errors.
(DIR) Post #B1Ev198UAxHxVyhJ7w by arcanechat@fosstodon.org
2025-12-14T10:17:43Z
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@david_chisnall by saying "requires phone numbers" I was implying that you can discover people by phone numbers since that is the case in 99% if not 100% of all apps that offer phone number registration, that you can disable this feature is meaningless if it is opt-out and most people will leave it like that, by saying ArcaneChat is immune to this I meant because you can't discover people like that, people must get in contact directly via QR or invite link
(DIR) Post #B1Ev19rrSFaJmhvXqy by david_chisnall@infosec.exchange
2025-12-14T10:22:57Z
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@arcanechat So there is no way for anyone to use a public identifier like an email address or similar to reach you?What do you put on business cards or similar if you want people to contact you? An invite link?
(DIR) Post #B1Ev1AS1HoVZaqqQDI by arcanechat@fosstodon.org
2025-12-14T10:26:49Z
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@david_chisnall #DeltaChat is for private chatting, so you normally don't put your link anywhere publicly, you could create a dedicated profile for public interactions tho, which, unlike in signal, it is super easy to do and you can have as many as you want,and notice the use case I am talking here is family chat, not business and public interactions, that is why I said "keep your family safe" I am talking about family chat solution here
(DIR) Post #B1Ev1B5MvVz3YtFqXw by david_chisnall@infosec.exchange
2025-12-14T12:47:56Z
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@arcanechat #DeltaChat is for private chatting, so you normally don't put your link anywhere publicly, you could create a dedicated profile for public interactions tho, which, unlike in signal, it is super easy to do and you can have as many as you want,Okay, so your use case for 'private chatting' excludes journalists publishing contact information for whistleblowers? It excludes union organisation? It excludes protest organisation?I guess that's fine, but maybe don't claim to be operating in the same space as Signal then.and notice the use case I am talking here is family chat, not business and public interactions, that is why I said "keep your family safe" I am talking about family chat solution hereThen you need to learn about the concept of an anonymity set. If you have one mechanism for talking to your family and another different one for talking to your union rep, it's really easy for a passive adversary to track when you suddenly start using a different mechanism for high-value conversations.
(DIR) Post #B1Ev9H3yaP9KPwSp4S by arcanechat@fosstodon.org
2025-12-14T10:24:28Z
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@david_chisnall > rather than just say ‘I don’t understand this attacks but the researchers who published it didn’t bother trying to attack the protocol I use and so I’m sure it is secure!’ That is exactly the attitude to security that makes me distrust DeltaChat.I don't understand why do you seem so upset, #DeltaChat has received several REAL PROFESSIONAL INDEPENDENT security audits, all listed here: https://delta.chat/en/help#security-auditscan you provide a similar list of REAL sec. audits for Signal?
(DIR) Post #B1Ev9I3IuOCpU99nf6 by david_chisnall@infosec.exchange
2025-12-14T12:51:22Z
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@arcanechat I don't understand why do you seem so upset,Because you're spreading misinformation to score marketing points and spreading misinformation about secure messengers gets people killed.I don't understand why do you seem so upset, #DeltaChat has received several REAL PROFESSIONAL INDEPENDENT security audits, all listed here: https://delta.chat/en/help#security-auSo, none after this particular class of attack was discovered and therefore none that include this in the threat model?