Readme.md

Merkle - Efficient calculation of merkle roots and proofs

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!")
}