add explanation about putty for windows

content/en/guides/register.md

@@ -66,6 +66,28 @@ The public key is what ~vern uses to verify its you, and you can send it to anyo
 
 It's absolutely important that you do not **ever** leak your private key otherwise anyone will be able to impersonate you and listen in to your communication with ~vern.
 
+### Windows 8 or below
+
+If you are using Windows 8 or below, ssh is not available directsly on the system, so you have to use another ssh implementation, there are multiple options for this, the most common one is Putty which is a Windows implementation of ssh client, sftp and ssh key management.
+
+The software is available for download from [Putty](https://www.chiark.greenend.org.uk/~sgtatham/putty/latest.html), you need at least putty.exe and puttygen.exe, also using pageant.exe is useful, so you might as well download the whole zip file.
+
+To create a ssh key, you can run puttygen.exe and click on generate, this will create a public/private key pair and you can choose which key algorithm you want, currently eddsa (ed25519) is recommended, but a rsa-4096 key will work as well. The eddsa key is much shorter and that is probably more convenient, also some servers might not support RSA for more security (some git servers seem to do that). For vern.cc both will work.
+
+The tool will take some time, you can speed that up by moving the mouse, when the key is finished it will show the public key and the key parameters and you can set a passphrase to protect the key that you will enter each time you use the key or when you load the key into the key agent and enter the passphrase once. This passphrase should be reasonably long so that it cannot be guessed, anybody who knows your passphrase and has the private key file can log into your accounts using the key.
+
+After creating the key, the dialogue will look like [this](/static/keygen.png).
+
+After you have created the key, be sure to save both the private keyfile and the public keyfile, the private key file will be e.g. ed.ppk, the public key file will be called ed.pub. The public key file is a single line text file that you need to send to the vern admins to request your account. You can also use the key displayed in the text field with copy-and-paste, that is the same text string.
+
+If you need the private key file in a format compatible to openssh (e.g. if you want to be able to do ssh from the vert.cc shell account to the git server), you need to open the .ppk file with puttygen.exe and export the key as openssh key file. By convention this file is usually called id_format without an extension, e.g. it might be called id_ed25519 but it can be any filename. If you use this private keyfile, you can use any openssh ssh client, e.g. if you use Cmder, Mobaxterm or any Cygwin, though in this case you could use the tools to create the keys to begin with and get the right format.
+
+If you use putty, you can add the key file to the session that you use for vern as described in the ssh article which will ask you for the passphrase each time you log in or you can use the pageant program to cache the key and use it without providing the passphrase. This is automatically picked up by putty and when you select agent forwarding, you can also use the private key on the shell session including using git with ssh without copying the file, however this has a security concern if you do not trust the shell host you log in since that might "borrow" your agent session if the admin is malicious (obviously we will trust the vern admins with that). If you use a putty session, you can turn agent forwarding on and off or if you use another ssh client, you can use -A to allow agent forwarding or leave it out if you do not need it.
+
+If you use the pageant program, other programs will be able to pick up the ssh key as well, e.g. some versions of git for windows, mobaxterm or the Winscp tool, so this is a rather useful tool to run.
+
+If you put it into your startup folder, you can add the name of the ppk file as a paramter, this way the program will ask you for your keyphrase when starting, otherwise you need to add the key with "Add key" or drag the file onto the pageant window.
+
 ## How to register an account at ~vern
 
 Now that you have an SSH key, we will finally register an account.
@@ -96,4 +118,4 @@ Now you can select what services you want, anything you select here will be regi
 
 Remember: there are no wrong answers here either, you can choose what you want and if something sounds boring to you then you are allowed to turn it off. You can always request an account by contacting the admins.
 
-Now that you are done, you can finally press submit, and a request to the admins will be sent. It will take around 48 hours for your account to be processed but when it does, you will be able to login to various ~vern services using the password located in `~/pass`.
+Now that you are done, you can finally press submit, and a request to the admins will be sent. It will take around 48 hours for your account to be processed but when it does, you will be able to login to various ~vern services using the password located in `~/pass`.