Os formatos de chave RSA parecem muito semelhantes a mim.
bash-4.1$ openssl genrsa 4096 > whoble
...
bash-4.1$ ssh-keygen -t rsa -N '' -f bobble
...
bash-4.1$ head -c 123 whoble ; echo
-----BEGIN RSA PRIVATE KEY-----
MIIJJwIBAAKCAgEAw22KzezlaVt6/lAkuTeLNVyrPIK8rjMchGPmUBp6Gx1Bkcjk
zjoWNNH1d0gxVd0Yw2RmpJVVnH
bash-4.1$ head -c 123 bobble ; echo
-----BEGIN RSA PRIVATE KEY-----
MIIEoQIBAAKCAQEA1tUSesz83DwMiQj6aWDMRd/5DISMBnp9jXZVzWwmD61FqlO/
ZhbmdBFMvNUIZNcHVQjqL/Gso0
bash-4.1$