The role of public key in Git is to encrypt the contents of the transfer.

It is well known that SSH is a cryptographic transmission.

There are many algorithms for encrypting transmission, GIT can use Rsa,rsa to solve a core problem is how to use a pair of specific numbers, so that one of the numbers can be used for encryption, and another number can be used to decrypt. These two numbers are the public key that you encounter when you use Git and GitHub, which is also the private key.

Where the public key is the number that is used to encrypt, which is why you have to upload it to GitHub after the local public key is generated. Sent back from the GitHub, with the public key encrypted data, you can use the local private key to restore.

If your key is lost, whether it's a public key or a private key, you can't use the missing one, the solution is simple, regenerate again, and then set it again in the github.com.