This is merkle, a Go package for computing the Merkle root hash of a sequence of byte strings, or of their hashes. It can also produce a compact proof that a given string belongs in a Merkle tree with a given root hash.
This implementation does not require holding all of the input in memory while computing a root hash or a proof. Instead, it is able to operate on a stream of input strings of unbounded length, holding incremental state that is only logarithmic [O(log N)] in the size of the input.
For more about Merkle trees, see the Wikipedia article.
Creating a merkle root hash:
var ch <-chan []byte // Represents some source of byte strings
tree := merkle.NewTree(sha256.New())
for str := range ch {
tree.Add(str)
}
fmt.Printf("merkle root hash is %x\n", tree.Root())Creating a merkle proof that ref belongs in the tree,
then verifying the proof:
var (
ch <-chan []byte // Represents some source of byte strings
rootHash []byte // Represents a previously computed merkle root hash (held by someone wishing to verify that ref is in the tree)
ref []byte // Represents the string to prove is a member of the tree with the given root hash
)
tree := merkle.NewProofTree(sha256.New(), ref)
for str := range ch {
tree.Add(str)
}
proof := tree.Proof() // This is a compact object. For verification purposes, tree can now be discarded.
// Verification:
if bytes.Equal(rootHash, proof.Hash(sha256.New(), ref)) {
fmt.Println("Verified!")
}