Lets say you have a private/public key pair that you use to login to your server via SSH and you lose the public key, either it was deleted or corrupt and you don’t want to have to regenerate a new pair what options do you have? In this post I will demonstrate how to regenerate a public key from the corresponding private key that you still have.

Generate public key and store into a file

Depends on the algorithm. Armies of exigo key generator. With RSA, you cannot, with EC you can. However, the public key is usually always stored together with the private key (not the other way around, though, of course), so this is not really a problem (if you have the private key, the same file also includes the public key). In a nutshell, you will generate a public and private key pair. The public key will be placed on the server by your system administrator, giving you access. You will keep the file containing the private key in a safe place. You’ll login by simply by providing that private key file to your SSH or SFTP supporting client. The.pub file is your public key, and the other file is the corresponding private key. If you don’t have these files (or you don’t even have a.ssh directory), you can create them by running a program called ssh-keygen, which is provided with the SSH package on Linux/macOS systems and comes with Git for Windows. Nov 01, 2018  A private key can be use to sign a document and the public key is use to verify that the signature of the document is valid. The API we use to generate the key pairs is in the java.security package. That’s mean we have to import this package into our code. The class for generating the key pairs is KeyPairGenerator.

Generate Public Key From Private Key

It is a simple one liner command to generate a public key from a private key, so lets say our private key is named ‘user@myserver.key’ and we want to generate the public key and name it ‘authorized_keys’. Below is the command to do this.