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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 | |
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6 | \C{pubkey} Using public keys for SSH authentication |
7 | |
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8 | \H{pubkey-intro} Public key authentication - an introduction |
9 | |
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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 | |
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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 | |
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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. |
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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 | |