signatures: with sync messages

Sync messages carry, for each actor's writes, the latest signature the
sender checked; the receiver checks it once it holds the change.

Auth plan M5.

1 files changed, 3 insertions, 0 deletions

diff --git a/docs/api.md b/docs/api.md
index 8f5b89c..cc3cc05 100644
--- a/docs/api.md
+++ b/docs/api.md
@@ -261,6 +261,9 @@ by the node's next signed one: with `--sign-every 1s` (the default), the node si
 latest change at most a second after it if nothing signed it before, so every change is vouched
 for within a second, at one signature a second at most; `--sign-every all` signs every
 change as it is made, and `--sign-every none` signs only those above.
+Signatures travel with sync messages: a node passes on, for each node's writes, the
+latest signature it checked, and checks one it receives once it holds the change (a
+signature costs about 30 µs to check, and one per node and run vouches for the rest).
 The signatures a node has are kept in its document file (`--document-file`) with the
 document.