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

   1 \define{versionidpgpkeys} \versionid $Id$
   2
   3 \A{pgpkeys} PuTTY download keys and signatures
   4
   5 \cfg{winhelp-topic}{pgpfingerprints}
   6
   7 \I{verifying new versions}We create \i{PGP signatures} for all the PuTTY
   8 files distributed from our web site, so that users can be confident
   9 that the files have not been tampered with. Here we identify
  10 our public keys, and explain our signature policy so you can have an
  11 accurate idea of what each signature guarantees.
  12 This description is provided as both a web page on the PuTTY site, and
  13 an appendix in the PuTTY manual.
  14
  15 As of the next release, all of the PuTTY executables will contain
  16 \#{XXX-REMOVE-BEFORE-RELEASE: fix this up for forthcoming release
  17 As of release 0.58, all of the PuTTY executables contain}
  18 fingerprint material (usually accessed via the \i\c{-pgpfp}
  19 command-line option), such that if you have an executable you trust,
  20 you can use it to establish a trust path, for instance to a newer
  21 version downloaded from the Internet.
  22
  23 (Note that none of the keys, signatures, etc mentioned here have
  24 anything to do with keys used with SSH - they are purely for verifying
  25 the origin of files distributed by the PuTTY team.)
  26
  27 \H{pgpkeys-pubkey} Public keys
  28
  29 We supply two complete sets of keys. We supply a set of RSA keys,
  30 compatible with both \W{http://www.gnupg.org/}{GnuPG} and PGP2,
  31 and also a set of DSA keys compatible with GnuPG.
  32
  33 In each format, we have three keys:
  34
  35 \b A Development Snapshots key, used to sign the nightly builds.
  36
  37 \b A Releases key, used to sign actual releases.
  38
  39 \b A Master Key. The Master Key is used to sign the other two keys, and
  40 they sign it in return.
  41
  42 Therefore, we have six public keys in total:
  43
  44 \b RSA:
  45 \W{http://www.chiark.greenend.org.uk/~sgtatham/putty/keys/master-rsa.asc}{Master Key},
  46 \W{http://www.chiark.greenend.org.uk/~sgtatham/putty/keys/release-rsa.asc}{Release key},
  47 \W{http://www.chiark.greenend.org.uk/~sgtatham/putty/keys/snapshot-rsa.asc}{Snapshot key}
  48
  49 \lcont{
  50 Master Key: 1024-bit; \I{PGP key fingerprint}fingerprint:
  51 \cw{8F\_15\_97\_DA\_25\_30\_AB\_0D\_\_88\_D1\_92\_54\_11\_CF\_0C\_4C}
  52 }
  53
  54 \b DSA:
  55 \W{http://www.chiark.greenend.org.uk/~sgtatham/putty/keys/master-dsa.asc}{Master Key},
  56 \W{http://www.chiark.greenend.org.uk/~sgtatham/putty/keys/release-dsa.asc}{Release key},
  57 \W{http://www.chiark.greenend.org.uk/~sgtatham/putty/keys/snapshot-dsa.asc}{Snapshot key}
  58
  59 \lcont{
  60 Master Key: 1024-bit; fingerprint:
  61 \cw{313C\_3E76\_4B74\_C2C5\_F2AE\_\_83A8\_4F5E\_6DF5\_6A93\_B34E}
  62 }
  63
  64 \H{pgpkeys-security} Security details
  65
  66 The various keys have various different security levels. This
  67 section explains what those security levels are, and how far you can
  68 expect to trust each key.
  69
  70 \S{pgpkeys-snapshot} The Development Snapshots keys
  71
  72 These keys are stored \e{without passphrases}. This is
  73 necessary, because the snapshots are generated every night without
  74 human intervention, so nobody would be able to type a passphrase.
  75
  76 The actual snapshots are built on a team member's home Windows box.
  77 The keys themselves are stored on an independently run Unix box
  78 (the same one that hosts our Subversion repository). After
  79 being built, the binaries are uploaded to this Unix box and then
  80 signed automatically.
  81
  82 Therefore, a signature from one of the Development Snapshots keys
  83 \e{DOES} protect you against:
  84
  85 \b People tampering with the PuTTY binaries between the PuTTY web site
  86 and you.
  87
  88 But it \e{DOES NOT} protect you against:
  89
  90 \b People tampering with the binaries before they are uploaded to the
  91 independent Unix box.
  92
  93 \b The sysadmin of the independent Unix box using his root privilege to
  94 steal the private keys and abuse them, or tampering with the
  95 binaries before they are signed.
  96
  97 \b Somebody getting root on the Unix box.
  98
  99 Of course, we don't believe any of those things is very likely. We
 100 know our sysadmin personally and trust him (both to be competent and
 101 to be non-malicious), and we take all reasonable precautions to
 102 guard the build machine. But when you see a signature, you should
 103 always be certain of precisely what it guarantees and precisely what
 104 it does not.
 105
 106 \S{pgpkeys-release} The Releases keys
 107
 108 The Release keys have passphrases and we can be more careful about
 109 how we use them.
 110
 111 The Release keys are kept safe on the developers' own local
 112 machines, and only used to sign releases that have been built by
 113 hand. A signature from a Release key protects you from almost any
 114 plausible attack.
 115
 116 (Some of the developers' machines have cable modem connections and
 117 might in theory be crackable, but of course the private keys are
 118 still encrypted, so the crack would have to go unnoticed for long
 119 enough to steal a passphrase.)
 120
 121 \S{pgpkeys-master} The Master Keys
 122
 123 The Master Keys sign almost nothing. Their purpose is to bind the
 124 other keys together and certify that they are all owned by the same
 125 people and part of the same integrated setup. The only signatures
 126 produced by the Master Keys, \e{ever}, should be the signatures
 127 on the other keys.
 128
 129 We intend to arrange for the Master Keys to sign each other, to
 130 certify that the DSA keys and RSA keys are part of the same setup.
 131 We have not yet got round to this at the time of writing.
 132
 133 We have collected a few third-party signatures on the Master Keys,
 134 in order to increase the chances that you can find a suitable trust
 135 path to them. We intend to collect more. (Note that the keys on the
 136 keyservers appear to have also collected some signatures from people
 137 who haven't performed any verification of the Master Keys.)
 138
 139 We have uploaded our various keys to public keyservers, so that
 140 even if you don't know any of the people who have signed our
 141 keys, you can still be reasonably confident that an attacker would
 142 find it hard to substitute fake keys on all the public keyservers at
 143 once.