git.distorted.org.uk Git - u/mdw/putty/blob - doc/pubkey.but

   1 \versionid $Id: pubkey.but,v 1.2 2001/02/06 09:34:42 owen Exp $
   2
   3 \# FIXME: passphrases, examples (e.g what does a key for pasting into
   4 \# authorized_keys look like?), index entries, links.
   5
   6 \C{pubkey} Using public keys for SSH authentication
   7
   8 \H{pubkey-intro} Public key authentication - an introduction
   9
  10 \# Explain the basic principles of public key authentication. Many
  11 \# people don't have the faintest idea what it is or why it's good.
  12
  13 \# Explain the dangers of leaving an unprotected private key around.
  14 \# Explain passphrases, and urge that people NEVER store
  15 \# unpassphrased keys unless they really need to or they can be sure
  16 \# the machine is secure.
  17
  18 \H{pubkey-puttygen} PuTTYgen: RSA key generator for PuTTY
  19
  20 PuTTYgen is a key generator. It generates pairs of public and private
  21 keys to be used with PuTTY, PSCP, and Plink, as well as the PuTTY
  22 authentication agent, Pageant (see \k{pageant}).  PuTTYgen generates
  23 RSA keys.
  24
  25 When you run PuTTYgen you will see a window where you have two
  26 choices: \e{Generate} new public/private key pair or \e{Load} an
  27 existing private key.
  28
  29 \S{pubkey-puttygen-generate} Generate a new key
  30
  31 Before generating a new key you have to chose the strength of the
  32 encryption. With \e{Parameters} you define the strength of the key. The
  33 default of 1024 should be OK for most users.
  34
  35 Pressing the \e{Generate} button starts the process of generating a
  36 new key pair. You then have to move the mouse over the blank area in
  37 order to generate random data for the algorithm. Continue until the
  38 progress bar is complete.
  39
  40 As soon as enough random data is available the key is generated.  This
  41 may take a little while, especially on slow machines.  Once the key is
  42 generated, its details appear in the \e{Key} part of the PuTTYgen
  43 window.
  44
  45 Now you can change the \e{Key comment} to something more meaningful
  46 than the default (which is based on the current date).  e.g. add the
  47 name of the host you will use it for. When using multiple keys a
  48 meaningful comment may help you remember which passphrase to use!  You
  49 should always enter a \e{Key passphrase} and \e{Confirm passphrase} to
  50 protect your keys.
  51
  52 \# Mention a good length for a passphrase. (I think Schneier
  53 \# said something about this on counterpane.com once.)
  54
  55 \# In case people don't like the idea of exchanging a short password
  56 \# typed every time for a longer passphrase typed every time, link
  57 \# to the Pageant chapter.
  58
  59 Finally save the key by pressing the \e{Save} button. Do not close the
  60 window but proceed with step \k{pubkey-gettingready}, otherwise you
  61 will have to \e{Load} the private key again as described below.
  62
  63 \S{pubkey-puttygen-load} Load and modify a key
  64
  65 PuTTYgen does not store the public key in a file by default. If you
  66 have to distribute the public key you can press the \e{Load} button,
  67 select the private key file, and PuTTYgen will give you the public key
  68 again.  You can also change the comment and passphrase for your
  69 private key this way. Just modify the values and \e{Save} the key.
  70
  71 \S{pubkey-gettingready} Getting ready for public key authentication
  72
  73 Connect to your SSH server using PuTTY with the SSH protocol. When the
  74 connection succeeds you will be prompted for your user name and
  75 password to login. Once logged in change into the \c{.ssh} directory
  76 and open the file \c{authorized_keys} with your favorite editor (you
  77 may have to create this file if this is the first key to add).
  78
  79 Switch to the PuTTYgen window and select all of the content below
  80 \e{Public key for pasting into authorized_keys file}, copy it to the
  81 clipboard (\c{Ctrl+C}). Then, switch back to the PuTTY window and
  82 insert the data into the open file. Save the file.
  83
  84 From now on you can use the private key for authentication to this
  85 host.  Either select the private key in PuTTY's \e{Connection},
  86 \e{SSH} panel: \e{Private key file for authentication} dialog or use
  87 it with Pageant as described in \k{pageant}.
  88
  89