Error: Failure checking encryption consistency

Support
1

I have 2 home PCs (Windows) set up to synchronise both a user “personal files” folder, and a “shared data” folder. This been working well for several months.

I have now installed Linux (KDE Neon, which is Ubuntu-based) on one of the machines, so I wanted to replicate the same simple setup.

This looked ok to begin with but syncing stopped after a few seconds and I am getting the error “Failure checking encryption consistency with device ”

The machines are both on the same home LAN and the shared folders are set to “Send&Receive” at both ends

The problem is similar to the situation reported in Failure to Sync: Failure checking encryption consistency, however in my case the error is persistent and has survived over a couple of days and multiple reboots of the machines

---- Details ----

Machine 1

OS: KDE Neon (Linux 6.11.0-17-generic #17~24.04.2-Ubuntu) Syncthing: syncthing v1.29.2 “Gold Grasshopper” (go1.23.4 linux-amd64)

Machine 2

OS: Windows 11 Pro 64bit Syncthing: v1.29.2, Windows (64-bit Intel/AMD)

Error Info (Machine 1)

Machine 1 shows Machine 2 as “Disconnected”. The address block shows:

dynamic
quic://<local ip>:22000
quic://89.241.217.23:22000
no recent network activity (01:07:33)
tcp://<local ip>:22000
tcp://89.241.217.23:22000
connection refused (01:07:28)

Error Info (Machine 2)

Machine 2 shows Machine 1 as “Disconnected”. Address block:

dynamic
relay://185.148.3.189:22067
quic://<local ip>:22000
tcp://<local ip>:22000
tcp://<local ipv6>:22000
quic://<local ipv6>:22000
quic://89.241.217.23:22000
no recent network activity (03:05:27)
tcp://89.241.217.23:22000
connection refused

Tail of error log (Machine 1)

2025-02-24 12:35:15 Lost primary connection to <machine 1> at <machine 1 ip>:22000-<machine 2 ip>:22000/tcp-server/TLS1.3-TLS_AES_128_GCM_SHA256/LAN-P10-6174K61D1QOJ0597L76664V632: handling cluster-config: remote expects to exchange plain data, but local data is encrypted (folder-type receive-encrypted) (0 remain)
2025-02-24 12:35:15 Connection to <machine 1> at <machine 1 ip>:22000-<machine 2 ip>:22000/tcp-server/TLS1.3-TLS_AES_128_GCM_SHA256/LAN-P10-6174K61D1QOJ0597L76664V632 closed: handling cluster-config: remote expects to exchange plain data, but local data is encrypted (folder-type receive-encrypted)

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Syncthing_20250224_123933565×399 35.8 KB
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Syncthing_20250224_123934451×338 37.9 KB
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Syncthing_20250224_123935451×381 44 KB

2

You appear to have a configuration mismatch where the device expects to be untrusted but the other side is sending plaintext data. Either set the other side to send encrypted data (ie set a password) or set this side to be a regular folder type.

3

Yes. Like you I read that in the error messages.

However, as I said in the description, and showed in the screenshots, all the sync relationships are set to “Send&Receive”.

4

Please make sure that the remote device in question on either side isn’t set to “Untrusted” (in the Advanced tab in the Edit Device window), and also that there are no passwords set for the folder (in the Sharing tab in the Edit Folder window).

5

I ended up clearing down the whole setup. I kept the installations intact but rebuilt the sync pairs from scratch.

The two machines are now talking. Not sure what was wrong, possibly a typo somewhere, but at least now it’s trying.