Functions {encode|decode}Secret.

1 files changed, 24 insertions, 0 deletions

diff --git a/src/Crypto/Tox.hs b/src/Crypto/Tox.hs
index c8b3665f..b84e5df6 100644
--- a/src/Crypto/Tox.hs
+++ b/src/Crypto/Tox.hs
@@ -43,6 +43,8 @@ module Crypto.Tox
     , zeros24
     , decryptSymmetric
     , encryptSymmetric
+    , encodeSecret
+    , decodeSecret
     ) where
 
 import Control.Arrow
@@ -53,6 +55,7 @@ import Crypto.ECC.Class
 import qualified Crypto.Error           as Cryptonite
 import qualified Crypto.MAC.Poly1305    as Poly1305
 import Crypto.PubKey.Curve25519
+import Data.Bits
 import qualified Data.ByteArray         as BA
          ;import Data.ByteArray         as BA (ByteArrayAccess, Bytes)
 import Data.ByteString                  as B
@@ -356,3 +359,24 @@ getPublicKey = throwCryptoError . publicKey <$> S.getBytes 32
 putPublicKey :: PublicKey -> S.Put
 putPublicKey bs = S.putByteString $ BA.convert bs
 
+encodeSecret :: BA.ByteArrayAccess bin => bin -> Maybe C8.ByteString
+encodeSecret k = do
+    (a,bs) <- BA.uncons (BA.convert k)
+    (cs,c) <- unsnoc bs
+    let a' = shiftR a 1 .|. (shiftR c 4 .&. 0x03)
+        c' = shiftL c 4
+        xs = Base64.encode $ cs `BA.snoc` a' `BA.snoc` c'
+        (ys,ds) = BA.splitAt 40 xs
+    return $ BA.index ds 0 `BA.cons` ys `BA.snoc` BA.index ds 1
+
+decodeSecret :: C8.ByteString -> Maybe C8.ByteString
+decodeSecret k64 = do
+    (ds0,ysds1) <- BA.uncons k64
+    (ys,ds1) <- unsnoc ysds1
+    let k64' = B.append ys (BA.cons ds0 (BA.cons ds1 "A="))
+    k <- either (const Nothing) Just $ Base64.decode k64'
+    (csa,c') <- unsnoc k
+    (cs,a') <- unsnoc csa
+    let a = shiftL (a' .&. 0x7c) 1
+        c = shiftR c' 4 .|. (shiftL a' 4 .&. 0x30) .|. 0x40
+    return $ a `BA.cons` (cs `BA.snoc` c)