使用Ruby和net-ssh，如何使用Net :: SSH.start中的key_data参数进行身份验证？

I've read the net-ssh documentation, and I am still perplexed. I can authenticate manually (using ssh -i ...), and also by placing the key in a file and using the :keys parameter. However, I dont want to use the :keys parameter, I want to use the :key_data parameter. Can anyone give a working example? For some reason, directly feeding a string into :key_data is not working, and it gives the error: "Neither PUB key nor PRIV key:: nested asn1 error". Of course I googled that, and it basically tells me to make sure the key is in PEM format. And, of course it is. Any ideas? I can provide more detailed info if needed...I've read the net-ssh documentation, and I am s