CODEWITHSUNDEEP
linuxubuntuubuntu-14.04
vher
vher

Reputation: 21

How to convert id_rsa.pub to id_rsa?

basically my computer bug down earlier and can no longer retrieve my files from my SSD HD.

i have my id_rsa.pub with me since I emailed this to our support team before for me to access the servers.

now I execute this command "ssh-keygen -t rsa" to my computer to generate new pub key.

upon checking the file is inside .ssh and i just replace the id_rsa.pub with the file i have on my email and leave id_rsa as it is.

trying out to access the server but always give me an error "Permission denied (publickey)."

it could be because of id_rsa which is still the latest.

any way i could replace the value based on the pubkey i have?

thanks.

Upvotes: 0

Views: 2469

Answers (2)

Zeimyth
Zeimyth

Reputation: 1395

Simply put, no.

The big idea behind public key cryptography is that the private key (in this case, id_rsa) is always hidden and secure, and only one person (or computer) has access to it. The public key (id_rsa.pub) provides just enough information that it is safe for anyone in the world to have access to it. If you could retrieve the original private key from the public key, then your private key would not be secure1.

The new keypair that you generated is totally distinct from your old one. Whatever server you are trying to ssh into is expecting to see the request signed with your old private key. Since you don't have access to it anymore, you can't sign the request with the correct key, and the server is rejecting your ssh attempt with a public key error.

So, basically, because you lost access to your private key, you can no longer ssh using that keypair.

Your administrative team will need to put your new public key onto the server so that you can ssh using the new key.

1 Note: It is theoretically possible to generate a private key that would match an existing public key, but this process is computationally intractable. Digicert estimates that this would take 6.4 quadrillion years for a 2048-bit RSA key.

Upvotes: 5

Bierbarbar
Bierbarbar

Reputation: 1479

normally you have a private part of a rsa key and a public one. You spread the public key out to the internet. Now you can sign with the private key you packages or data, and everyone how knows you public key can check if this data or package is from you. So it's possible to generate a public key from a private, but i is impossible to generate a private key out of a public key in a acceptable time. So you need to generate a new one on you computer and need to put the new generated public key on your server, and you will have access again.

Upvotes: 0

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