2 files changed, 17 insertions, 1 deletions

diff --git a/src/Data/Torrent/JSON.hs b/src/Data/Torrent/JSON.hs
index 3fa8973d..6a0aa510 100644
--- a/src/Data/Torrent/JSON.hs
+++ b/src/Data/Torrent/JSON.hs
@@ -3,9 +3,14 @@ module Data.Torrent.JSON
        , omitRecordPrefix
        ) where
 
+import Control.Applicative
 import Data.Aeson.TH
+import Data.Aeson.Types
+import Data.ByteString as BS
+import Data.ByteString.Base16 as Base16
 import Data.Char
 import Data.List as L
+import Data.Text.Encoding as T
 
 
 -- | Ignore '_' prefix.
@@ -28,4 +33,14 @@ mapWhile p f = go
 omitRecordPrefix :: Options
 omitRecordPrefix = omitLensPrefix
   { fieldLabelModifier = mapWhile isUpper toLower . L.dropWhile isLower
-  }
\ No newline at end of file
+  }
+
+instance ToJSON ByteString where
+  toJSON = String . T.decodeUtf8 . Base16.encode
+
+instance FromJSON ByteString where
+  parseJSON v = do
+    (ok, bad) <- (Base16.decode . T.encodeUtf8) <$> parseJSON v
+    if BS.null bad
+      then return ok
+      else fail   "parseJSON: unable to decode ByteString"
diff --git a/src/Network/BitTorrent/Core/PeerId.hs b/src/Network/BitTorrent/Core/PeerId.hs
index c860d9d4..f8d69e8b 100644
--- a/src/Network/BitTorrent/Core/PeerId.hs
+++ b/src/Network/BitTorrent/Core/PeerId.hs
@@ -62,6 +62,7 @@ import Text.PrettyPrint hiding ((<>))
 import Text.PrettyPrint.Class
 import Text.Read        (readMaybe)
 
+import Data.Torrent.JSON ()
 import Network.BitTorrent.Core.Fingerprint
 
 -- TODO use unpacked Word160 form (length is known statically)