rend-spec: document MAC_KEY_LEN=32.
We use this constant in various places throughout the document but we never say what it is.
(Please don't merge this until @dgoulet says that the repository is open for merges again!)
We use this constant in various places throughout the document but we never say what it is.
(Please don't merge this until @dgoulet says that the repository is open for merges again!)