when I do an apt-get update I get the following error message:
An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: https://apt.z.cash jessie Release: Die folgenden Signaturen waren ungültig: F1E214037E94E950BA8577B263C4A2169C1B2FA2
Seems that the signature is not valid anymore?
Do you have this problem too? Any idea what I can do to fix it?