// Hash hashes the data in a chunk into a cas.Key.
//
// Hash makes sure to never return a Special Key.
func Hash(chunk *chunks.Chunk) cas.Key {
var pers [blake2.PersonalSize]byte
copy(pers[:], personalizationPrefix)
copy(pers[len(personalizationPrefix):], chunk.Type)
config := &blake2.Config{
Size: cas.KeySize,
Personal: pers[:],
Tree: &blake2.Tree{
// We are faking tree mode without any intent to actually
// follow all the rules, to be able to feed the level
// into the hash function. These settings are dubious, but
// we need to do something to make having Tree legal.
Fanout: 0,
MaxDepth: 255,
InnerHashSize: cas.KeySize,
NodeDepth: chunk.Level,
},
}
h := blake2.New(config)
if len(chunk.Buf) == 0 {
return cas.Empty
}
_, _ = h.Write(chunk.Buf)
keybuf := h.Sum(nil)
return makeKey(keybuf)
}
func (s *Convergent) computeBoxedKey(key []byte) []byte {
conf := blake2.Config{
Size: cas.KeySize,
Key: s.secret[:],
Personal: personalizeKey,
}
h := blake2.New(&conf)
// hash.Hash docs say it never fails
_, _ = h.Write(key)
return h.Sum(nil)
}
// Nonce summarizes key, type and level so mismatch of e.g. type can
// be detected.
func (s *Convergent) makeNonce(key []byte) *[nonceSize]byte {
conf := blake2.Config{
Size: nonceSize,
Personal: personalizeNonce,
}
h := blake2.New(&conf)
// hash.Hash docs say it never fails
_, _ = h.Write(key)
var ret [nonceSize]byte
h.Sum(ret[:0])
return &ret
}