How to convert SSH keypairs generated using PuTTYgen (Windows) into key-pairs used by ssh-agent and Keychain (Linux)

user_212942 0
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I've generated key pairs using PuTTYgen and been logging in using Pageant, so that I have to enter my pass-phrase only once when my system boots.

How do I achieve this in Linux? I've heard of keychain but I hear that it uses a different key pair format - I don't want to change my Windows keys and it would be nice if I could seamlessly connect in the same manner in both Windows and Linux.

pageant ssh-keys keychain putty git
10 Answers

puttygen supports exporting your private key to an OpenSSH compatible format. You can then use OpenSSH tools to recreate the public key.

  1. Open PuttyGen
  2. Click Load
  3. Load your private key
  4. Go to Conversions->Export OpenSSH and export your private key
  5. Copy your private key to ~/.ssh/id_dsa (or id_rsa).

  6. Create the RFC 4716 version of the public key using ssh-keygen

    ssh-keygen -e -f ~/.ssh/id_dsa > ~/.ssh/id_dsa_com.pub

  7. Convert the RFC 4716 version of the public key to the OpenSSH format:

    ssh-keygen -i -f ~/.ssh/id_dsa_com.pub > ~/.ssh/id_dsa.pub

See this and this for more information.

user_1038420

If all you have is a public key from a user in PuTTY-style format, you can convert it to standard openssh format like so:

ssh-keygen -i -f keyfile.pub > newkeyfile.pub

References

Copy of article

I keep forgetting this so I'm gonna write it here. Non-geeks, just keep walking.

The most common way to make a key on Windows is using Putty/Puttygen. Puttygen provides a neat utility to convert a linux private key to Putty format. However, what isn't addressed is that when you save the public key using puttygen it won't work on a linux server. Windows puts some data in different areas and adds line breaks.

The Solution: When you get to the public key screen in creating your key pair in puttygen, copy the public key and paste it into a text file with the extension .pub. You will save you sysadmin hours of frustration reading posts like this.

HOWEVER, sysadmins, you invariably get the wonky key file that throws no error message in the auth log except, no key found, trying password; even though everyone else's keys are working fine, and you've sent this key back to the user 15 times.

ssh-keygen -i -f keyfile.pub > newkeyfile.pub

Should convert an existing puttygen public key to OpenSSH format.

user_1468210

It's probably easier to create your keys under linux and use PuTTYgen to convert the keys to PuTTY format.

PuTTY Faq: A.2.2

user_2689070

PPK → OpenSSH RSA with PuttyGen & Docker.

Private key:

docker run --rm -v $(pwd):/app zinuzoid/puttygen private.ppk -O private-openssh -o my-openssh-key

Public key:

docker run --rm -v $(pwd):/app zinuzoid/puttygen private.ppk -L -o my-openssh-key.pub

See also https://hub.docker.com/r/zinuzoid/puttygen

user_16691650

Even faster than reopening puttygen, what I have often done is:

  1. Duplicate the public key file.
  2. In the copy, place the word "ssh-rsa " at the beginning.
  3. Remove the begin/end comment lines and all other line breaks.
  4. Save. The result is a one line key that works for openssh.
user_39107490
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