diff options
Diffstat (limited to 'Shard.hs')
| -rw-r--r-- | Shard.hs | 56 |
1 files changed, 47 insertions, 9 deletions
@@ -1,22 +1,60 @@ +{-# LANGUAGE OverloadedStrings, MultiParamTypeClasses #-} + module Shard where import Types -import Serialization +import Tunables +import ExpensiveHash import Cost import qualified Crypto.SecretSharing as SS +import qualified Data.ByteString as B import qualified Data.ByteString.Lazy as BL -import Raaz.Core.Encode (toByteString, fromByteString) +import qualified Raaz.Core.Encode as Raaz +import qualified Raaz.Hash.Sha256 as Raaz +import qualified Data.Text as T +import qualified Data.Text.Encoding as E import Data.Binary +import Data.Monoid + +data ShardIdents = ShardIdents + { getIdents :: [StorableObjectIdent] + , identsCreationCost :: Cost CreationOp + , identsBruteForceCalc :: CostCalc BruteForceOp UnknownName + } + +instance Bruteforceable ShardIdents UnknownName where + getBruteCostCalc = identsBruteForceCalc + +-- | Generates identifiers to use for storing shards. +-- +-- This is an expensive operation, to make it difficult for an attacker +-- to brute force known/guessed names and find matching shards. +-- The keyid is used as a salt, both to avoid collisions when the same +-- name is chosen for multiple keys, and to prevent the attacker +-- from using a rainbow table from names to expensivehashes. +shardIdents :: Tunables -> Name -> KeyId -> ShardIdents +shardIdents tunables (Name name) keyid = + ShardIdents idents creationcost bruteforcecalc + where + (ExpensiveHash creationcost basename) = + expensiveHash tunables (Salt keyid) name + mk n = StorableObjectIdent $ Raaz.toByteString $ mksha $ + E.encodeUtf8 $ basename <> T.pack (show n) + mksha :: B.ByteString -> Raaz.Base16 + mksha = Raaz.encode . Raaz.sha256 + idents = map mk [1..totalObjects (head (shardParams tunables))] + bruteforcecalc = bruteForceLinearSearch creationcost -genShards :: EncryptedSecretKey -> ShardParams -> IO [StorableObject] -genShards esk ps = +genShards :: EncryptedSecretKey -> Tunables -> IO [StorableObject] +genShards (EncryptedSecretKey esk _) tunables = map (StorableObject . encode) <$> SS.encode - (neededObjects ps) - (totalObjects ps) - (BL.fromStrict (toByteString esk)) + (neededObjects $ head $ shardParams tunables) + (totalObjects $ head $ shardParams tunables) + (BL.fromStrict esk) -- Throws AssertionFailed if the number of shares is too small. -combineShards :: [StorableObject] -> Maybe EncryptedSecretKey -combineShards = fromByteString . BL.toStrict . SS.decode . map conv +combineShards :: [StorableObject] -> EncryptedSecretKey +combineShards = mk . BL.toStrict . SS.decode . map conv where conv = decode . fromStorableObject + mk b = EncryptedSecretKey b unknownCostCalc |