SSH (Secure Shell) keys are used for secure authentication and access to Oracle Cloud Infrastructure (OCI) instances. Here are the key aspects of using SSH keys in OCI:

1. SSH Key Pair: To access OCI instances securely, you typically use an SSH key pair consisting of a public key and a private key. The public key is placed on the target instance, and the private key is kept securely on your local machine.
2. Key Generation: You can generate an SSH key pair using tools like OpenSSH on your local machine. The private key should be kept confidential, and the public key should be uploaded to your OCI account.
3. Adding SSH Public Key to OCI:

• • In the OCI Console, navigate to the “Identity” section.
  • Click on “Users” and select the user for whom you want to add the SSH key.
  • Under the “Resources” tab, locate the “API Keys” section.
  • Click on “Add Public Key” and paste your SSH public key.
  • The SSH key is now associated with the user, allowing them to access instances.

1. SSH Key Authentication: When you launch or access an OCI instance, you specify the SSH private key file as part of the authentication process. The private key is used to verify your identity, and if it matches the public key on the instance, access is granted.
2. Instance Metadata: OCI instances have instance metadata accessible via HTTP. You can retrieve the SSH public key for an instance from its metadata to enable secure access.
3. SSH Bastion Host: For enhanced security, OCI recommends using a bastion host (also known as a jump host) to access instances in a private subnet securely. This involves SSHing into the bastion host first and then accessing other instances from there.
4. Key Rotation: It’s essential to periodically rotate SSH keys for security reasons. You can remove old SSH keys from the OCI Console and add new ones.
5. IAM Policies: You can use Identity and Access Management (IAM) policies to control who can access instances and manage SSH keys. IAM policies help enforce the principle of least privilege.
6. SSH Tunneling: SSH keys can also be used to set up SSH tunnels for secure data transfer between your local machine and OCI resources.
7. SSH Key Management: Properly manage and secure your SSH private keys, as they provide access to your OCI resources. Use passphrase protection for added security.