Messages cannot be decrypted [DC 1.2.15, failed: PGP: MissingKey]

[csb0730]

Delta Chat version

1.2.15

Expected behavior

Messages from another Deltachat should be decrypted and shown.

Actual behavior

1. Text-messages from another Deltachat (encrypted) are not shown.
   Instead following standard message appears:

   […] – [Diese Nachricht kann nicht entschlüsselt werden.
   • Es könnte bereits helfen, einfach auf diese Nachricht zu antworten und die/den AbsenderIn zu bitten, die Nachricht erneut zu senden.
   • Falls Delta Chat oder ein anderes E-Mail-Programm auf diesem oder einem anderen Gerät neu installiert wurde, kann von dort aus eine Autocrypt Setup-Nachricht gesendet werden.]

   When replying on this message my reply on opposite Deltachat is not shown!

2. When sending a picture from another Deltachat this is shown as required !

This behaviour came up around Feb 13th. Maybe this is a hint for finding root cause.

As I can see that unencrypted messages are received at my device I suspect an issue in autocrypt processing. Unfortunately I cannot workaround this behaviour in disabling autocrypt setting “prefer end to end encryption”.
In the moment it’s not possible for me to send any message to another Deltachat client any more.

Steps to reproduce the problem

Use current Deltachat version and send a text messge in a 1:1 chat to an older Deltachat like mine?

Debug logs

04-07 20:05:08.786 4230 4363 I DeltaChat: ThreadId(5) src/dc_receive_imf.rs: 42: => Receiving message INBOX/84323…
04-07 20:05:08.856 4230 4363 I DeltaChat: ThreadId(5) src/e2ee.rs : 277: Detected Autocrypt-mime message
04-07 20:05:08.856 4230 4363 W DeltaChat: ThreadId(5) src/mimeparser.rs : 135: decryption failed: PGP: MissingKey

Conclusion:

As debug log shows a PGP fault I think somewhere in autocrypt process there is an issue in newer Deltachat versions than Feb 13th or a little bit earlier.
I see this misbehaviour at all messages from all my friends using current Deltachat version!

Any help required.

[csb0730]

When I open a replied message from a current Deltachat in Thunderbird now please see picture:

Please excuse but I have only a german environment available!

Before Feb 13th these messages has been decrypted as required.

[anedroid]

Yeah, same problem here - which forced me to upgrade DC on all my fellow’s devices. Unfortunately, upgrade didn’t cause the previous messages to decrypt - only new ones, which is especially troublesome for WebXDC stuff we relied on. Waiting for devs to respond on Resend webxdc sent by another user [to fix group that became plaintext on 2.46] - #4 by anedroid

[ian]

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[link2xt]

The message in the screenshot is showing that incoming message has anonymous Key IDs (0x000…000). Old Delta Chat cannot decrypt such messages:

PSA: Known interoperability problem in chatmail core <1.160.0

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