// Update updates balloon with the slice of events, producing the next snapshot.
// Run by the author on trusted input.
func (balloon *Balloon) Update(events []Event, current *Snapshot,
sk []byte) (next *Snapshot, err error) {
if len(events) == 0 {
return nil, errors.New("you need to add at least one event")
}
if !util.Equal(current.Roots.History, balloon.history.Root()) ||
!util.Equal(current.Roots.Treap, balloon.treap.Root()) {
return nil, errors.New("provided snapshot is not current")
}
sort.Sort(ByKey(events))
// attempt to add events
treap := balloon.treap
ht := balloon.history.Clone()
for i := 0; i < len(events); i++ {
// add the hash of the entire event to the history tree
_, err = ht.Add(util.Hash(append(events[i].Key, events[i].Value...)))
if err != nil {
return
}
// add to the treap the hash of the key pointing to the index (version) of the
// hash of the event in the history tree
treap, err = treap.Add(util.Hash(events[i].Key), util.Itob(ht.LatestVersion()))
if err != nil {
return
}
}
// attempt to create next snapshot
next = new(Snapshot)
next.Index = current.Index + 1
next.Roots.History = ht.Root()
next.Roots.Treap = treap.Root()
next.Roots.Version = ht.LatestVersion()
next.Previous = current.Signature
signature, err := util.Sign(balloon.sk,
append(append([]byte("snapshot"), next.Roots.History...), append(next.Roots.Treap, next.Previous...)...))
if err != nil {
panic(err)
}
next.Signature = signature
// all is OK, save result
err = balloon.Storage.Store(events, *next)
if err != nil {
return nil, err
}
balloon.latestsnapshot = *next
if len(events) > 0 {
balloon.latesteventkey = events[len(events)-1].Key
}
balloon.treap = treap
balloon.history = ht
return
}
// Setup creates a new balloon based on the slice of events (may be empty or nil). Returns the
// first snapshot. Run by the author on trusted input.
func Setup(events []Event, sk, vk []byte, storage EventStorage) (balloon *Balloon, snap *Snapshot, err error) {
balloon = NewBalloon(storage)
balloon.sk = sk
balloon.vk = vk
// do same as update, allow events to be empty
if len(events) > 0 {
sort.Sort(ByKey(events))
// add events
for i := 0; i < len(events); i++ {
// add the hash of the entire event to the history tree
_, err = balloon.history.Add(util.Hash(append(events[i].Key, events[i].Value...)))
if err != nil {
return nil, nil, err
}
// add to the treap the hash of the key pointing to the index (version) of the
// hash of the event in the history tree
balloon.treap, err = balloon.treap.Add(util.Hash(events[i].Key),
util.Itob(balloon.history.LatestVersion()))
if err != nil {
return nil, nil, err
}
}
}
// create first snapshot
snap = new(Snapshot)
snap.Index = 0
snap.Roots.History = balloon.history.Root()
snap.Roots.Treap = balloon.treap.Root()
snap.Roots.Version = balloon.history.LatestVersion()
snap.Previous = nil
signature, err := util.Sign(balloon.sk,
append(append([]byte("snapshot"), snap.Roots.History...), append(snap.Roots.Treap, snap.Previous...)...))
if err != nil {
panic(err)
}
snap.Signature = signature
// actually store events
err = balloon.Storage.Store(events, *snap)
if err != nil {
return nil, nil, err
}
balloon.latestsnapshot = *snap
if len(events) > 0 {
balloon.latesteventkey = events[len(events)-1].Key
}
return
}
// Update creates the next snapshot from adding the provided events in the balloon
// fixed by the current snapshot. This function depends on that the provided prune proof has
// been successfully verified for the answer true.
// Run by the author on input that should have been verified before by using Verify.
func (proof *PruneProof) Update(events []Event, current *Snapshot,
sk []byte) (next *Snapshot, err error) {
sort.Sort(ByKey(events))
// calculate balloon internal keys and values based on events
startIndex := current.Roots.Version + 1
values := make([][]byte, len(events))
treapKeys := make([][]byte, len(events))
treapValues := make([][]byte, len(events))
for i := 0; i < len(events); i++ {
values[i] = util.Hash(append(events[i].Key, events[i].Value...))
treapKeys[i] = util.Hash(events[i].Key)
treapValues[i] = util.Itob(startIndex + i)
}
// calculate updated commitment on the history tree
c, version, err := proof.QueryProof.HistoryProof.Update(values)
if err != nil {
return nil, err
}
// calculate updated hash treap root
root, err := proof.TreapProof.Update(treapKeys, treapValues)
if err != nil {
return nil, err
}
next = new(Snapshot)
next.Index = current.Index + 1
next.Roots.History = c
next.Roots.Treap = root
next.Roots.Version = version
next.Previous = current.Signature
signature, err := util.Sign(sk,
append(append([]byte("snapshot"), next.Roots.History...),
append(next.Roots.Treap, next.Previous...)...))
if err != nil {
panic(err)
}
next.Signature = signature
return
}