From 7192abc5d53aa5a6ee609ed30bd05f1575e67b65 Mon Sep 17 00:00:00 2001
From: Joey Hess <joeyh@joeyh.name>
Date: Sat, 6 Aug 2016 17:35:10 -0400
Subject: some basic data types and expensive hashing

---
 ExpensiveHash.hs | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)
 create mode 100644 ExpensiveHash.hs

(limited to 'ExpensiveHash.hs')

diff --git a/ExpensiveHash.hs b/ExpensiveHash.hs
new file mode 100644
index 0000000..8bfe004
--- /dev/null
+++ b/ExpensiveHash.hs
@@ -0,0 +1,54 @@
+{-# LANGUAGE OverloadedStrings #-}
+
+module ExpensiveHash where
+
+import Types
+import qualified Data.ByteString as B
+import Raaz.Core.Encode
+import qualified Crypto.Argon2 as Argon2
+import Data.Time.Clock
+import Control.DeepSeq
+
+-- | A hash that is expensive to calculate.
+--
+-- This is a lynchpin of keysafe's security, because using this hash
+-- as an encryption key forces brute force attackers to generate
+-- hashes over and over again, taking a very long time.
+data ExpensiveHash = ExpensiveHash Cost B.ByteString
+	deriving (Show)
+
+data Salt t = Salt t
+
+expensiveHash :: Encodable t => RunMode -> Salt t -> Password -> ExpensiveHash
+expensiveHash runmode (Salt s) (Password password) = 
+	ExpensiveHash cost $ Argon2.hash o password (toByteString s)
+  where
+	HashParams o cost = hashParams runmode
+
+data HashParams = HashParams Argon2.HashOptions Cost
+
+hashParams :: RunMode -> HashParams
+hashParams SecureMode = HashParams o cost
+  where
+	-- argon2 is GPU and ASIC resistent, so it uses CPU time.
+	-- The selected HashOptions were benchmarked at 661 seconds CPU time
+	-- on a 2 core Intel(R) Core(TM) i5-4210Y CPU @ 1.50GHz.
+	cost = CPUCost (Seconds 600)
+	o = Argon2.HashOptions
+		{ Argon2.hashIterations = 10000
+		, Argon2.hashMemory = 131072 -- 128 mebibtyes per thread
+		, Argon2.hashParallelism = 4 -- 4 threads
+		, Argon2.hashVariant = Argon2.Argon2i
+		}
+hashParams TestingMode =
+	HashParams Argon2.defaultHashOptions $ CPUCost (Seconds 0)
+
+benchmarkExpensiveHash :: IO (Benchmark Cost)
+benchmarkExpensiveHash = do
+	start <- getCurrentTime
+	let ExpensiveHash expected b = expensiveHash SecureMode
+		(Salt (KeyIdent gpgKey (Name ("benchmark" :: B.ByteString))))
+		(Password ("himom" :: B.ByteString))
+	end <- b `deepseq` getCurrentTime
+	let actual = (CPUCost $ Seconds $ end `diffUTCTime` start)
+	return $ Benchmark { expectedBenchmark = expected, actualBenchmark = actual }
-- 
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