If I use ssh-agent instead of seahorse, it works. Seahorse never even asks for a passphrase for the key. Hence, I think it's a seahorse bug.
You can use ssh-agent instead by editing /etc/X11/Xsession.d/60seahorse and adding unset SSH_AUTH_SOCK -- ssh Agent admitted failure to sign using the key https://bugs.launchpad.net/bugs/201786 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
