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{-# LANGUAGE GeneralizedNewtypeDeriving, MultiParamTypeClasses, EmptyDataDecls #-}
{- Copyright 2016 Joey Hess <id@joeyh.name>
-
- Licensed under the GNU AGPL version 3 or higher.
-}
module Types.Cost where
-- | An estimated cost to perform an operation.
data Cost op
= CPUCost Seconds Divisibility
-- ^ cost in Seconds, using 1 physical CPU core
deriving (Show, Eq, Ord)
newtype Seconds = Seconds Rational
deriving (Num, Fractional, Real, RealFrac, Eq, Ord)
instance Show Seconds where
show (Seconds n) = show (fromRational n :: Double) ++ "s"
-- | How many CPU cores a single run of an operation can be divided amoung.
newtype Divisibility = Divisibility Integer
deriving (Show, Eq, Ord)
data UsingHardware = UsingCPU | UsingGPU | UsingASIC
deriving (Show)
instance Monoid (Cost t) where
mempty = CPUCost (Seconds 0) (Divisibility 1)
CPUCost (Seconds a) (Divisibility x) `mappend` CPUCost (Seconds b) (Divisibility y) =
-- Take maximum divisibility, to avoid over-estimating
-- the total cost.
CPUCost (Seconds (a+b)) (Divisibility $ max x y)
-- | Operations whose cost can be measured.
data DecryptionOp
data CreationOp
data BruteForceOp
-- | Things that track their creation cost.
class HasCreationCost t where
getCreationCost :: t -> Cost CreationOp
-- | Things that track their decryption cost.
class HasDecryptionCost t where
getDecryptionCost :: t -> Cost DecryptionOp
-- | Calculation of a cost that depends on some amount of entropy.
type CostCalc op t = Entropy t -> Cost op
unknownCostCalc :: CostCalc op t
unknownCostCalc = \_e -> error "No cost calculation available"
-- | Number of bits of entropy
newtype Entropy t = Entropy Int
deriving (Num, Show)
class CalcEntropy d t where
calcEntropy :: d -> Entropy t
-- | Entropy can never go negative when subtracting bits from it.
reduceEntropy :: Entropy t -> Int -> Entropy t
reduceEntropy (Entropy a) b = Entropy (max 0 (a - b))
-- | Things that can be brute-forced track their CostCalc.
class Bruteforceable t a where
getBruteCostCalc :: t -> CostCalc BruteForceOp a
-- | Things that can have entropy
data UnknownPassword
data UnknownName
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