document hmac algorithm

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>

diff --git a/PROTOCOL b/PROTOCOL
index e18cf0e1554da169e6ffdcd8994ba3a727f8c17c..1a385c3a143e93f180159f4d0347cd9d0618c474 100644 (file)
--- a/PROTOCOL
+++ b/PROTOCOL
@@ -29,7 +29,7 @@ Authentication token is:
         <time_t in hex with no leading 0s> <hmac in base64>
 (separated by a single space).  The hmac is
         HMAC(secret, <time_t in hex>)
-
+and the hash function is SHA256
 
 Possible future nonce-based authentication: