Bitcoin.Crypto.Hash.KDF

Key Derivation Functions (KDF).

These are used to derive larger symmetric keys from a small (say, 256 bit) shared secret generated using eg. Diffie-Hellman key exchange.

Documentation

newtype SharedSecret

Constructors

SharedSecret [Word8]

Instances

Eq SharedSecret

Methods

(==) :: SharedSecret -> SharedSecret -> Bool

(/=) :: SharedSecret -> SharedSecret -> Bool

Ord SharedSecret

Methods

compare :: SharedSecret -> SharedSecret -> Ordering

(<) :: SharedSecret -> SharedSecret -> Bool

(<=) :: SharedSecret -> SharedSecret -> Bool

(>) :: SharedSecret -> SharedSecret -> Bool

(>=) :: SharedSecret -> SharedSecret -> Bool

max :: SharedSecret -> SharedSecret -> SharedSecret

min :: SharedSecret -> SharedSecret -> SharedSecret

Show SharedSecret

Methods

showsPrec :: Int -> SharedSecret -> ShowS

show :: SharedSecret -> String

showList :: [SharedSecret] -> ShowS

OctetStream SharedSecret

Methods

toByteString :: SharedSecret -> ByteString

toWord8List :: SharedSecret -> [Word8]

unsafeToCharList :: SharedSecret -> [Char]

toIntegerLE :: SharedSecret -> Integer

toIntegerBE :: SharedSecret -> Integer

fromByteString :: ByteString -> SharedSecret

fromWord8List :: [Word8] -> SharedSecret

fromCharList :: [Char] -> SharedSecret

fromIntegerLE :: Integer -> SharedSecret

fromIntegerBE :: Integer -> SharedSecret

concatenatingKDF

Arguments

:: OctetStream publicInfo

=> SharedSecret

shared secret (for example estabilished by Diffie-Hellman key exchange)

-> publicInfo

publicly avaliable information about the parties (for example, the IDs of the two parties)

-> Int

desired output length

-> ByteString

Concatenation-based Key Derivation Function.

Basically:

output = Hash[1] || Hash[2] || Hash[3] || ...

Hash[counter] = H ( counter || Z || publicInfo )

where H is the SHA256 hash function, Z is the shared secret, and the counter is a big-endian encoded 32 bit word.

This is more-or-less the NIST-800-56-Concatenation-KDF standard.

foldingKDF

Arguments

:: OctetStream publicInfo

=> SharedSecret

shared secret (for example estabilished by Diffie-Hellman key exchange)

-> publicInfo

publicly avaliable information about the parties (for example, the IDs of the two parties)

-> Int

desired output length

-> ByteString

This is similar to the previous, however, we also use the previous hash when computing the next hash:

Hash[counter] = H ( counter || Hash[counter-1] || Z || publicInfo )

Hash[0] is set to ad-hoc value, presently [0x5c,0x5c,0x5c...]