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1. Embed this notice
   Harry Sintonen (harrysintonen@infosec.exchange)'s status on Saturday, 23-May-2026 08:25:10 JST Harry Sintonen

   #Signalapp doesn't actually delete messages when they're deleted (either manually or by automation). The message deletion is written to Write-ahead Log, and the data is only truly deleted once Signal is restarted or threshold of 1000 pages is reached. For macOS Signal application, extra complication arises from the fact that the signal message database can be backed up before the database consolidation occurs. Large amount of the supposedly already deleted messages could be recovered from the device or backups.

   This concerns use cases where deleting messages actually getting removed in timely manner is of high importance and recovery of the deleted messages could lead to grave consequences.

   TL;DR: If you don't care about deleted messages being actually deleted you don't need to worry.

   Full advisory at: https://sintonen.fi/advisories/signal-deleted-but-not-forgotten.txt

   #fulldisclosure #infosec #cybersecurity

   • Embed this notice
     clacke (clacke@libranet.de)'s status on Saturday, 23-May-2026 13:22:55 JST clacke

     in reply to

     • feld

     @feld @harrysintonen Who has been conflating cryptographic guarantees and message deletion?

     Genuine question; I haven't been following mass media or social media discourse over secure messengers. Has Signal been saying that their disappearing messages are better than those of other messengers because of how they are encrypted in transit?

   • Embed this notice
     feld (feld@friedcheese.us)'s status on Saturday, 23-May-2026 13:22:56 JST feld

     in reply to
     @harrysintonen
     
     > This concerns use cases where deleting messages actually getting removed in timely manner is of high importance and recovery of the deleted messages could lead to grave consequences.
     
     > TL;DR: If you don't care about deleted messages being actually deleted you don't need to worry.
     
     But this is the main selling point of Signal's Perfect Forward Secrecy that everyone says is so important and nobody should use a messenger without it...
     
     PFS isn't really about security in the normal sense, it's about the data transmitted being ephemeral and irrecoverable through cryptographic guarantees. That's why DeltaChat's upcoming implementation will not use the PFS terminology but will be called "reliable deletion".
     
     So now we have another case of Signal's PFS being broken: first through the iOS notification database not being cleared properly, now through MacOS not actually removing the deleted messages from the database.
     
     I think people need to stop trusting Signal's word and start demanding detailed proof that their security promises hold up on every platform.
   • Embed this notice
     svans (svans@mastodon.social)'s status on Thursday, 28-May-2026 15:10:46 JST svans

     in reply to

     @harrysintonen
     My schtick isn't "look how great Signal is" it's "why the fuck do you clowns keep trying to recommend shitty apps that cannot measure up to Signal?"

     Those aren't the same positions to take. I'm not putting Signal on a pedestal or declaring it infallible. I'm calling Signal the minimum bar to clear to be worth considering as secure end-to-end encryption.

     The attack that you're demanding I answer to is a local device attack.

     clacke likes this.