Private Key Format when using
ssh-keygen -t rsa -b 4096 -f ~/.ssh/check
-----BEGIN OPENSSH PRIVATE KEY-----
b3BlbnNzaC1rZXktdjEAAAAACmFlczI1Ni1j
...
-----END OPENSSH PRIVATE KEY-----
This format is not accepted some of applications.
Command for generating Private Key in correct RSA Format
ssh-keygen -m PEM -t rsa -b 4096 -f ~/.ssh/check
-----BEGIN RSA PRIVATE KEY-----
Proc-Type: 4,ENCRYPTED
DEK-Info: AES-128-CBC,1CD1F5D28E9D7ACD1334BA78B00E7646
oxfZCcieJ2T2gNTv1f1nRQVOc129VUr+MZEEUNE6LFVmuP6gTBVUmr6chiD4cfK7
...
-----END RSA PRIVATE KEY-----
Command for correcting the already generated Private Key to RSA Format
ssh-keygen -p -m PEM -f ~/.ssh/check