ssh-keygen does not create RSA private key

Solution 1:

I faced the same problem recently (after upgrade to mojave 10.14.1), here are 2 possible solutions for this issue.

• Downgrade your ssh-keygen binary (you can easily get old version from any linux/docker image)

OR

• Add option -m PEM into your ssh-keygen command. For example, you can run ssh-keygen -m PEM -t rsa -b 4096 -C "[email protected]" to force ssh-keygen to export as PEM format.

It seems like in the current ssh-keygen version in mojave, the default export format is RFC4716 as mentioned here

Solution 2:

New keys with OpenSSH private key format can be converted using ssh-keygen utility to the old PEM format.

ssh-keygen -p -m PEM -f ~/.ssh/id_rsa

There is no need to downgrade to older OpenSSH just to achieve this result.