Key-Pair to Bastion EC2 instance

Hello,

The .pem key is given to you when you create the key. If you lose the key, you may need to generate another key.

Please follow this documentation: How can I connect to my Amazon EC2 instance if I lost my SSH key pair after its initial launch?

You can look into alternatives like EC2 Instance Connect and System manager. Below blogs provide a detailed information on each

1. You can use AWS Systems Manager Session Manager to securely connect to your private instances in your virtual private cloud (VPC) without needing an intermediary bastion host, open ports, or a key pair assigned to the instances - Reference : https://aws.amazon.com/blogs/infrastructure-and-automation/toward-a-bastion-less-world/
2. How you can improve the security of your existing bastion hosts by using Amazon Elastic Compute Cloud (Amazon EC2) Instance Connect - Reference : https://aws.amazon.com/blogs/infrastructure-and-automation/securing-your-bastion-hosts-with-amazon-ec2-instance-connect/