From 94d351004688992f8aeac7d03da55d179ef50e8c Mon Sep 17 00:00:00 2001
From: Joey Hess <joeyh@joeyh.name>
Date: Sat, 6 Aug 2016 21:39:38 -0400
Subject: more cost calculation and refactored Tunables

---
 Encryption.hs | 42 +++++++++++++++++++++++++++++++-----------
 1 file changed, 31 insertions(+), 11 deletions(-)

(limited to 'Encryption.hs')

diff --git a/Encryption.hs b/Encryption.hs
index 083aedd..98afdfd 100644
--- a/Encryption.hs
+++ b/Encryption.hs
@@ -3,23 +3,37 @@
 module Encryption where
 
 import Types
+import Cost
+import Tunables
 import ExpensiveHash
 import qualified Data.ByteString as B
 import Raaz.Core.Encode
 import qualified Raaz.Cipher.AES as AES
 import Data.Word
+import Data.Monoid
 
 -- | An AES key, which is used to encrypt the key that is stored
 -- in keysafe.
-newtype KeyEncryptionKey = KeyEncryptionKey AES.KEY256
+data KeyEncryptionKey = KeyEncryptionKey
+	AES.KEY256
+	(Cost DecryptionOp) 
+	(CostCalc BruteForceOp UnknownPassword)
 
--- | An ExpensiveHash of the KeyIdent and a RandomObstacle are combined
--- to form the AES key.
---
--- An attacker has to brute force both, while a legitimate user
--- only has to brute force the RandomObstacle.
-genKeyEncryptionKey :: KeyIdent -> Password -> KeyEncryptionKey
-genKeyEncryptionKey = undefined
+-- | The ExpensiveHash of the Password is combined with a 
+-- RandomObstacle to form the AES key. Combination method is logical OR.
+genKeyEncryptionKey :: Tunables -> KeyIdent -> Password -> KeyEncryptionKey
+genKeyEncryptionKey tunables keyident password =
+	KeyEncryptionKey k decryptcost bruteforcecalc
+  where
+	k = undefined -- hashb <> ob -- TODO use logical OR
+	(ExpensiveHash hashcost hashb) = expensiveHash tunables salt password
+	salt = Salt keyident
+	(RandomObstacle ob) = genRandomObstacle decryptcost
+	decryptcost = CombinedCost (decryptionCost tunables) (castCost hashcost)
+	-- To brute force data encrypted with this key,
+	-- an attacker needs to pay the decryptcost for each password
+	-- checked.
+	bruteforcecalc = bruteForceLinearSearch decryptcost
 
 -- | A random value which adds difficulty to decrypting, since it's never
 -- written down anywhere and must always be brute-forced.
@@ -32,7 +46,13 @@ genKeyEncryptionKey = undefined
 --
 -- The fewer leading 0's and thus longer the random bits,
 -- the harder it is.
-data RandomObstacle = RandomObstacle Word64
+data RandomObstacle = RandomObstacle B.ByteString
 
-genRandomObstacle :: Int -> RandomObstacle
-genRandomObstacle difficulty = undefined
+-- | Generate a random obstacle that will add the specified cost to AES
+-- decryption.
+--
+-- AES can be calculated more efficiently by a GPU, so the cost must be
+-- a GPU cost.
+genRandomObstacle :: Cost DecryptionOp -> RandomObstacle
+genRandomObstacle (GPUCost c) = undefined
+genRandomObstacle _ = error "decryptionCost must be a GPUCost"
-- 
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