// Retrieve an object in a Merkle tree,
// validating the entire path in the process.
// Returns a slice of a buffer obtained from HashGet.Get(),
// which might be shared and should be considered read-only.
func MerkleGet(suite abstract.Suite, root []byte, path MerklePath,
ctx hashid.HashGet) ([]byte, error) {
// Follow pointers through intermediate levels
blob := root
for i := range path.Ptr {
beg := path.Ptr[i]
// end := beg + suite.HashLen()
end := beg + 256 // change me: find hash len
if end > len(blob) {
return nil, errors.New("bad Merkle tree pointer offset")
}
id := hashid.HashId(blob[beg:end])
b, e := ctx.Get(id) // Lookup the next-level blob
if e != nil {
return nil, e
}
blob = b
}
// Validate and extract the actual object
beg := path.Ofs
end := beg + path.Len
if end > len(blob) {
return nil, errors.New("bad Merkle tree object offset/length")
}
return blob[beg:end], nil
}
// Generate a Merkle proof tree for the given list of leaves,
// yielding one output proof per leaf.
func ProofTree(newHash func() hash.Hash, leaves []hashid.HashId) (hashid.HashId, []Proof) {
if len(leaves) == 0 {
return hashid.HashId(""), nil
}
// Determine the required tree depth
nleavesArg, nleaves := len(leaves), len(leaves)
depth := 0
for n := 1; n < nleaves; n <<= 1 {
depth++
}
// if nleaves is not a power of 2, we add 0s to fill in up to pow2
var i int
for nleaves, i = (1 << uint(depth)), nleavesArg; i < nleaves; i++ {
leaves = append(leaves, make([]byte, newHash().Size()))
}
// fmt.Println("depth=", depth, "nleaves=", nleavesArg)
// Build the Merkle tree
c := hashContext{newHash: newHash}
tree := make([][]hashid.HashId, depth+1)
tree[depth] = leaves
nprev := nleaves
tprev := tree[depth]
for d := depth - 1; d >= 0; d-- {
nnext := (nprev + 1) >> 1 // # hashes total at level i
nnode := nprev >> 1 // # new nodes at level i
// println("nprev", nprev, "nnext", nnext, "nnode", nnode)
// fmt.Println("nprev", nprev, "nnext", nnext, "nnode", nnode)
tree[d] = make([]hashid.HashId, nnext)
tnext := tree[d]
for i := 0; i < nnode; i++ {
tnext[i] = c.hashNode(nil, tprev[i*2], tprev[i*2+1])
}
// If nnode < nhash, just leave the odd one nil.
nprev = nnext
tprev = tnext
}
if nprev != 1 {
panic("oops")
}
root := tprev[0]
// Build all the individual proofs from the tree.
// Some towards the end may end up being shorter than depth.
proofs := make([]Proof, nleaves)
for i := 0; i < nleaves; i++ {
p := make([]hashid.HashId, 0, depth)
// p = append(p, root)
for d := depth - 1; d >= 0; d-- {
h := tree[depth-d][sibling(i>>uint(d))]
if h != nil {
p = append(p, h)
}
}
proofs[i] = Proof(p)
}
return root, proofs[:nleavesArg]
}
func (s *Server) AggregateCommits(view int) []byte {
//log.Println(s.Name(), "calling AggregateCommits")
s.mux.Lock()
// get data from s once to avoid refetching from structure
Queue := s.Queue
READING := s.READING
PROCESSING := s.PROCESSING
// messages read will now be processed
READING, PROCESSING = PROCESSING, READING
s.READING, s.PROCESSING = s.PROCESSING, s.READING
s.Queue[READING] = s.Queue[READING][:0]
// give up if nothing to process
if len(Queue[PROCESSING]) == 0 {
s.mux.Unlock()
s.Root = make([]byte, hashid.Size)
s.Proofs = make([]proof.Proof, 1)
return s.Root
}
// pull out to be Merkle Tree leaves
s.Leaves = make([]hashid.HashId, 0)
for _, msg := range Queue[PROCESSING] {
s.Leaves = append(s.Leaves, hashid.HashId(msg.Tsm.Sreq.Val))
}
s.mux.Unlock()
// non root servers keep track of rounds here
if !s.IsRoot(view) {
s.rLock.Lock()
lsr := s.LastRound()
mr := s.maxRounds
s.rLock.Unlock()
// if this is our last round then close the connections
if lsr >= mr && mr >= 0 {
s.closeChan <- true
}
}
// create Merkle tree for this round's messages and check corectness
s.Root, s.Proofs = proof.ProofTree(s.Suite().Hash, s.Leaves)
if sign.DEBUG == true {
if proof.CheckLocalProofs(s.Suite().Hash, s.Root, s.Leaves, s.Proofs) == true {
log.Println("Local Proofs of", s.Name(), "successful for round "+strconv.Itoa(int(s.LastRound())))
} else {
panic("Local Proofs" + s.Name() + " unsuccessful for round " + strconv.Itoa(int(s.LastRound())))
}
}
return s.Root
}
func (sn *Node) SetBackLink(Round int) {
prevRound := Round - 1
sn.Rounds[Round].BackLink = hashid.HashId(make([]byte, hashid.Size))
if prevRound >= FIRST_ROUND {
// My Backlink = Hash(prevRound, sn.Rounds[prevRound].BackLink, sn.Rounds[prevRound].MTRoot)
h := sn.suite.Hash()
if sn.Rounds[prevRound] == nil {
log.Errorln(sn.Name(), "not setting back link")
return
}
h.Write(intToByteSlice(prevRound))
h.Write(sn.Rounds[prevRound].BackLink)
h.Write(sn.Rounds[prevRound].MTRoot)
sn.Rounds[Round].BackLink = h.Sum(nil)
}
}