Cross-reference all the host key docs.

[PuTTY.git] / doc / using.but

diff --git a/doc/using.but b/doc/using.but
index 0a05c2e27d35bbcaa4fe371fbe1f15b44ba89b59..dc0d6b9b4a691194347eb2e0463d5418047c28e1 100644 (file)
--- a/doc/using.but
+++ b/doc/using.but
@@ -201,6 +201,28 @@ resets associated timers and counters). For more information about
 repeat key exchanges, see \k{config-ssh-kex-rekey}.
 }
 
+\b \I{host key cache}Cache new host key type
+
+\lcont{
+Only available in SSH-2. This submenu appears only if the server has
+host keys of a type that PuTTY doesn't already have cached, and so
+won't use. Selecting a key here will allow PuTTY to use that key now
+and in future: PuTTY will do key here will cause a fresh key-exchange
+with the selected key, and immediately add that key to PuTTY's
+permanent cache (relying on the host key used at the start of the
+connection to cross-certify the new key). That key will be used for
+the rest of the current session; it may not actually be used for
+future sessions.
+
+Normally, PuTTY will carry on using a host key it already knows, even
+if the server offers key formats that PuTTY would otherwise prefer,
+to avoid host key prompts. As a result, if you've been using a server
+for some years, you may still be using an older key than a new user
+would use, due to server upgrades in the meantime. The SSH protocol
+unfortunately does not have organised facilities for host key migration
+and rollover, but this allows you to manually upgrade.
+}
+
 \b \I{Break, SSH special command}Break
 
 \lcont{
@@ -912,22 +934,22 @@ authentication} box in the Auth panel of the PuTTY configuration box
 \S2{using-cmdline-loghost} \i\c{-loghost}: specify a \i{logical host
 name}
 
-This option overrides PuTTY's normal SSH host key caching policy by
-telling it the name of the host you expect your connection to end up
-at (in cases where this differs from the location PuTTY thinks it's
-connecting to). It can be a plain host name, or a host name followed
-by a colon and a port number. See \k{config-loghost} for more detail
-on this.
+This option overrides PuTTY's normal SSH \I{host key cache}host key
+caching policy by telling it the name of the host you expect your
+connection to end up at (in cases where this differs from the location
+PuTTY thinks it's connecting to). It can be a plain host name, or a
+host name followed by a colon and a port number. See
+\k{config-loghost} for more detail on this.
 
 \S2{using-cmdline-hostkey} \i\c{-hostkey}: \I{manually configuring
 host keys}manually specify an expected host key
 
-This option overrides PuTTY's normal SSH host key caching policy by
-telling it exactly what host key to expect, which can be useful if the
-normal automatic host key store in the Registry is unavailable. The
-argument to this option should be either a host key fingerprint, or an
-SSH-2 public key blob. See \k{config-ssh-kex-manual-hostkeys} for more
-information.
+This option overrides PuTTY's normal SSH \I{host key cache}host key
+caching policy by telling it exactly what host key to expect, which
+can be useful if the normal automatic host key store in the Registry
+is unavailable. The argument to this option should be either a host key
+fingerprint, or an SSH-2 public key blob. See
+\k{config-ssh-kex-manual-hostkeys} for more information.
 
 You can specify this option more than once if you want to configure
 more than one key to be accepted.