From 686dcc8b172b77e3e612ba4badbb88879d0f5599 Mon Sep 17 00:00:00 2001 From: Joey Hess Date: Thu, 27 Apr 2017 15:26:50 -0400 Subject: Leave the prevMessage out of Activity serialization to save BW. Do include it in the data that gets signed, so it can be recovered by trying each likely (recently seen) Activity as the prevMessage, and checking the signature. The UserState and DeveloperState already had the necessary state about recently seen hashes, so this does not impact data use. One tricky bit is that relayFromSocket needs to wait for the TMChan to be empty before calling restorePrevActivityHash. Otherwise, the hashes of items in the channel that have not been processed yet won't be tried. The TMChan is not really being used as a channel since only 1 item can be in it. It could be converted to a TMVar, but closeTMChan is used so I left it as a channel. Note that the server does not restore hashes of messages that pass through it; it's just a dumb relay. Sending a single key press now only needs 94 bytes of data to be sent, down from 169! --- Also switched to SHA512, since hashes are no longer being sent over the wire and so the larger size does not matter. SHA512 is slightly faster and more secure. This commit was sponsored by Ewen McNeill. --- Hash.hs | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'Hash.hs') diff --git a/Hash.hs b/Hash.hs index 3bfb5a2..3cc8d94 100644 --- a/Hash.hs +++ b/Hash.hs @@ -12,8 +12,8 @@ class Hashable a where hash :: a -> Hash instance Hashable B.ByteString where - -- Encodes the SHA256 using base16 format - hash = Hash SHA256 . Val . C8.pack . show . sha256 + -- Encodes the SHA512 using base16 format + hash = Hash SHA512 . Val . C8.pack . show . sha512 instance Hashable Val where hash (Val v) = hash v @@ -21,8 +21,8 @@ instance Hashable Val where instance Hashable Hash where hash = id -sha256 :: B.ByteString -> H.Digest H.SHA256 -sha256 = H.hash +sha512 :: B.ByteString -> H.Digest H.SHA512 +sha512 = H.hash -- | A value tagged with a ByteString describing the type of value. -- This is hashed by hashing the concacenation of the hash of the -- cgit v1.2.3