diff --git a/docs/set_up_build_environments.md b/docs/set_up_build_environments.md
index 925ad0b..b6f82d8 100644
--- a/docs/set_up_build_environments.md
+++ b/docs/set_up_build_environments.md
@@ -176,6 +176,12 @@ Setting up an actual server is similar to setting up the virtual machine
 modelling it, except you have to worry about the server getting overloaded
 and locking up.
 
+On an actual server, you probably want to totally disable passwords by corrupting the shadow file once you have `ssh` working.
+
+```bash
+usermod -L root
+```
+
 If a server is configured with an [ample swap file] an overloaded server will
 lock up and have to be ungracefully powered down, which can corrupt the data
 on the server. If the swap file is inadequate, the OOM killer will shut
diff --git a/docs/social_networking.md b/docs/social_networking.md
index 8aab0e7..d9263f3 100644
--- a/docs/social_networking.md
+++ b/docs/social_networking.md
@@ -264,6 +264,31 @@ So, you can navigate to whole world’s public conversation through
 approved links and reply-to links – but not every spammer, scammer, and
 shill in the world can fill your feed with garbage.
 
+## Algorithm and data structure.
+
+For this to work, the underlying structure needs to be something based on
+the same principles as Git and git repositories, except that Git relies on
+SSL and the Certificate Authority system to locate a repository, which
+dangerous centralization would fail under the inevitable attack.  It needs to
+ have instead for its repository name system a Kamelia distributed has
+table within which local repositories find the network addresses of remote
+repositories on the basis of the public key of a Zooko identity of a person
+who pushed a tag or a branch to that repository, a branch being a thread,
+and the branch head in this case being the most recent response to a thread
+by a person you are following.
+
+The messages of the people you are following are likely to be in a
+relatively small number of repositories, even if the total number of
+repositories out there is enormous and the number of hashes in each
+repository is enormous, so this algorithm and data structure will scale, and
+the responses to that thread that they have approved, by people you are not
+following, will be commits in that repository, that, by pushing their latest
+response to that thread to  a public repository, they committed to that
+repository.
+
+Each repository contains all the material the poster has approved, resulting
+in considerable duplication, but not enormous duplication.
+
 The underlying protocol and mechanism is that when you are following
 Bob, you get a Bob feed from a machine controlled by Bob, or controlled
 by someone that Bob has chosen to act on his behalf, and that when Bob