"PuTTY key format too new" when using ppk file for PuTTY SSH key authentication

Question

I wanted to connect to my Unix server using SSH keys. For that I had converted my id_rsa file from ./ssh directory to a ppk file using PuTTYgen, but after loading my .ppk key I get this warning:

PuTTY key format too new

If I use my default id_rsa file, then I get error:

OpenSSH SSH-2 private key (old PEM format)

Either way I am getting stuck. Can anyone please help me?

Solution 1

Easy way to fix this issue, please follow the pictures.
Step1:
Step2:

Solution 2

If you have a key in the new PPK version 3 format, you can use PuTTYgen to export it to the old PPK version 2 format.

I don't know what Operating System you're using PuTTYgen/PuTTY on, but if it's Microsoft Windows you can set PPK Version 2 by default for PuTTYgen selecting in the app menu:

Key->Parameters for saving key files...->PPK file version: 2.

PuTTYgen: Private Key File Parameters

Solution 3

You have probably used a newer version of PuTTYgen than the version of PuTTY.

There's new PPK format since PuTTY 0.75 (released 2021-05-09). So I guess you have used PuTTYgen 0.75 (or newer) to convert your key. But you are trying to use it in an older version of PuTTY.

Solution 4

Install the Latest version of putty at least 0.75 it will work fine

Solution 5

I've put newer version of puttygen.exe and pageant.exe in TortoiseGit\bin folder and it works

View more solutions

Comments

[Robert]

TortoiseGIt bundles outdated putty executables (0.73/0.74). As you have identified this problem you should really open an Issue in the TortoiseGit tracker: gitlab.com/tortoisegit/tortoisegit/-/issues

[Machavity]

By the time I got here, I had already setup keys. Replacing the outdated Tgit ones worked well.

[Martin Prikryl]

So why would you mess with two versions of PuTTYgen, if you can do it with the new version of PuTTYgen only?

[Black]

I tried to load it in PuTTYgen, but it also says "too new"

[Martin Prikryl]

@Black You need to use the latest version of PuTTYgen. What makes sense only, if you are stuck with old version of PuTTY on some system, where you need to use the new key. You can download the new version of PuTTYgen on another system, convert the key there, and copy it to the system with the old PuTTY. If you are free to use newest software directly, then go for latest version of PuTTY, and you won't have to convert anything. Note that the OP created/converted the key with latest PuTTYgen, but is trying to use it with old PuTTY. See my answer.

[PandaWood]

After getting the same error, then doing this, I now get from Pageant "Couldn't load this key (Open SSH SSH-2 private key (old PEM format) - a rock and a hard place