Which of the below mentioned options can be a possible reason for rejection?
The private key file has the wrong file permission
The ppk file used for SSH is read only
The public key file has the wrong permission
The user has provided the wrong user name for the OS login
Explanations:
The Unprotected Private Key File error occurs when the permissions on the private key file are too open. For SSH to accept the key, it must be set to read/write for the user only (typicallychmod 600on Linux). If the permissions are more permissive (e.g., readable by group or others), SSH will reject it for security reasons.
A read-only.ppkfile (PuTTY private key) does not cause the Unprotected Private Key File error. While the file needs to be accessible for the SSH client to read it, being read-only does not affect its usability for authentication purposes as long as the permissions allow the user to read it.
The public key file’s permissions do not affect the ability to connect via SSH using a private key. The public key is typically placed in the~/.ssh/authorized_keysfile on the server, and its permissions do not need to be restricted like those of the private key.
Providing the wrong username can result in authentication failure, but it does not cause the Unprotected Private Key File error. This error specifically relates to the private key’s file permissions, not the username used for the connection.
I calculate that the answer is:
The private key file has the wrong file permission