add telehash design page; update roadmap

doc/design/assistant/telehash.mdwn

@@ -0,0 +1,60 @@
+[Telehash](http://telehash.org/) for secure P2P communication between
+git-annex (assistant) repositories.
+
+## telelhash implementation status
+
+* node.js version seems most complete
+* C version currently lacks channel support and seems buggy (13 Jan 2014)
+* No pure haskell implementation of telelhash v2. There was one of
+  telehash v1 (even that seems incomplete). I have pinged its author
+  to see if he anticipates updating it.
+* Rapid development, situation may change in a month or 2.
+
+## implementation basics
+
+* Add a telehash.log that maps between uuid and telehash address.
+* On startup, assistant creates a new telehash keypair if not already
+  present; stores this locally and generates a telehash address from it,
+  stored in telehash.log.
+* Use telehash for notifications of changes to the repository
+* Do git push over telehash. (Pretty easy, may need rate limiting in
+  situations involving relays.)
+* Remove git push over XMPP (which has several problems including
+  XMPP being an unreliable transport, requiring a separate XMPP account per
+  repo, and XMPP not being end-to-end encrypted)
+
+## telehash address discovery
+
+* Easy way is any set of repos that are already connected can communicate
+  them via telehash.log.
+* Local pairing can be used for telehash address discovery. Could be made
+  to work without ssh (with content transfer over telehash discussed
+  below).
+* XMPP pairing can also be used for telehash address discovery. (Note that
+  MITM attacks are possible.) Is it worth keeping XMPP in git-annex just
+  for this?
+* Telelhash addresses of repoitories can be communicated out of band (eg,
+  via an OTR session or gpg signed mail), and pasted into the webapp to
+  initiate a repository pairing that then proceeds entirely over telehash.
+  Once both sides do this, the pairing can proceed automatically.
+
+## content transfer over telehash
+
+* In some circumstances, it would be ok to do annexed content transfer
+  over telehash.  
+  Need to check if there are MTU problems with large data bodies in
+  telelhash messages.  
+  Probably not when a bridge is being used, due to required rate
+  limiting in bridging over telehash. Cloud transfer remotes still needed for
+  those situations.
+* On a LAN, telehash can be used to determine the current local IP address
+  of another computer on the LAN. The 2 could then determine if either uses
+  ssh and if so use regular git-annex-shell for transfers. Or could do
+  annexed content transfer directly over telelhash.
+
+## generic git-remote-telehash
+
+This might turn out to be easy to split off from git-annex, so `git pull`
+and `git push` can be used at the command line to access telehash remotes.
+Allows using general git entirely decentralized and with end-to-end
+encryption.

doc/design/assistant/xmpp_security.mdwn

@@ -24,3 +24,6 @@ AES encryption:
   * Rely on the user's gpg key, and do gpg key verification during XMPP
     pairing. Problimatic because who wants to put their gpg key on their
     phone? Also, require the users be in the WOT and be gpg literate.
+
+Update: This seems unlikely to be worth doing. [[Telehash]] is better.
+--[[Joey]]

doc/design/roadmap.mdwn

@@ -9,10 +9,10 @@ Now in the
 * Month 3 user-driven features and polishing [[todo/direct_mode_guard]] [[assistant/upgrading]]
 * Month 4 [[Windows_webapp|assistant/Windows]], Linux arm, [[todo/support_for_writing_external_special_remotes]]
 * **Month 5 user-driven features and polishing**
-* Month 6 [[!traillink assistant/xmpp_security]]
+* Month 6 get [[assistant/Android]] and Windows out of beta
 * Month 7 user-driven features and polishing
-* Month 8 [[!traillink assistant/gpgkeys]] [[!traillink assistant/sshpassword]]
-* Month 9 get [[assistant/Android]] and Windows out of beta
+* Month 8 [[!traillink assistant/telehash]]
+* Month 9 [[!traillink assistant/gpgkeys]] [[!traillink assistant/sshpassword]]
 * Month 10 user-driven features and polishing
 * Month 11 [[!traillink assistant/chunks]] [[!traillink assistant/deltas]]
 * Month 12 user-driven features and polishing