Unable to decrypt messages received when offline when using only in private/incognito mode

tx1683 commented 5 years ago

Description

When using in only one device in browser in private/incognito mode and using online backup most encrypted messages received when user is offline are undecryptable when logged in.

Steps to reproduce

Log in to Riot Web in browser private mode
Connect to key backup
Normal usage
Log out / close tab / close browser
Someone sends encrypted message
Log in
Connect to key backup
Most or all messages received when offline cannot be decrypted

Messages send to me, when my only device is offline should be encrypted using that device pubkey. When logged in with new key and then to online backup that messages should be decrypted using that key which was restored from backup.

Version information

Platform: web
Browser: Firefox 68.0.2 and earlier, all in private mode
OS: Arch Linux
URL: few self hosted instances and riot.im/app, all 1.3.2 and/or earlier

t3chguy commented 5 years ago

The issue is that when you log in you generate a new set of device keys, and any key rotations which happen while you have no active devices would go unnoticed

tx1683 commented 5 years ago

Key rotation in sender I presume? Shouldn't sender wait with rotating its keys when recipient is offline? Or any other solutions... That issue is making encryption pretty unusable for some people and is very annoying.

t3chguy commented 5 years ago

Key rotation happens whenever the device list changes (to prevent leaking encryption keys) and also periodically to provide forward secrecy

The issue is easily worked around by keeping a session alive on a mobile device

tx1683 commented 5 years ago

I know about this workaround, but in my use case it isn't practical, sadly. Is there any theoretical way to keep FS, and also deliver decryptable messages when recipient is offline?

turt2live commented 5 years ago

Closing in favour of cross-signing, which should address this sort of use case. Tracking issue is https://github.com/vector-im/riot-web/issues/9631

ghost commented 1 year ago

Closing in favour of cross-signing, which should address this sort of use case. Tracking issue is #9631

How does cross-signing help in this scenario?

element-hq / element-web