As of release 7.8 of openssh the default format of generated keys is the OPENSSH PRIVATE KEY format.
* ssh-keygen(1): write OpenSSH format private keys by default instead of using OpenSSL's PEM format. The OpenSSH format, supported in OpenSSH releases since 2014 and described in the PROTOCOL.key file in the source distribution, offers substantially better protection against offline password guessing and supports key comments in private keys. If necessary, it is possible to write old PEM-style keys by adding "-m PEM" to ssh-keygen's arguments when generating or updating a key.
This means, that the private key looks like this:
-----BEGIN OPENSSH PRIVATE KEY----- b3BlbnNzaC1rZXktdjEAAAAACmFlczI1Ni1jdHIAAAAGYmNyeXB0AAAAGAAAABCnz7UO3z wPva3ZeqAv3Fb3AAAAEAAAAAEAAABoAAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlz dHAyNTYAAABBBKHuAe5N1uLPUpY3t5kyYuISOxUobPZfK8H+CQaJTCALTMFrT63UDDYLyI 2xroS67T2bWHkuhX1BHiTGP6JpwL8AAACwwZ1jHlWJTZUwle+U8cXZx2Od0s4Y71qL9onX /+g+UVxaBeAZq88S8fbIPc1netiue9VVo7Qiw4e4WEPUCWKykQ+mwBX9798q/QUbrK3UZl 509ZLFe/DN41mVGO6rU6NHy+1mVstStgEEle7Dc+JaZwa/iZRVeRNq58MXQ5HBAO8fi4Y5 yhe050OWLkNylLtLOmRffRWo6eFg/DwCK64G5+qsSeTYVrt0nq/ffcvyovc= -----END OPENSSH PRIVATE KEY-----
If you are a user of the java library jsch, which is a java implementation of the ssh protocol, you were not able to use this keys, because it does not support it. you either had to create your keys with a flag or convert them to old pem format.
Now I have implemented support for the “proprietary” key format in the fork of jsch, which you can find at https://github.com/mwiede/jsch
Please upgrade to version 0.1.60 and give it a try.