serf supports one key can encrypt a message, but many keys can decrypt a message.?

For serf encryption/decryption using keyring file,
Let's have we have Node1 , Node 2, Node 3 with primary key k1.
Now Node 3 goes down.....In the meantime,,Node1 did (keygen,install,use) operations..
So Node 1, Node 2 are with K2(Primary key),K1(Secondary key)....Now Node 3 comes up..

1) Node 3 is unable to decrypt the messages coming from Node 1/Node 2 and he is creating a new cluster. How can we solve it?

2) How do we say serf supports one key can encrypt a message, but many keys can decrypt a message.

Serf version : 0.8.2