add audit proof

README.md

@@ -1,2 +1,74 @@
 # go-merkle-tree
-A Merkle tree, implemented in Golang
+
+> A Merkle Tree, implemented in Golang
+
+Many people have written many things about Merkle Trees. For a good overview (uses, characteristics, etc.), read Marc
+Clifton's [_Understanding Merkle Trees - Why use them, who uses them, and how to use them_][1].
+
+## Warning
+
+*Warning: This is alpha software.*
+
+## Usage
+
+### Construction
+
+```go
+data := [][]byte{[]byte("alpha"), []byte("beta"), []byte("kappa")}
+
+tree := CreateTree(Sha256DoubleHash, data)
+
+fmt.Println(tree.AsString(hex.EncodeToString, 0))
+
+/*
+
+output:
+
+(B root: 1add1cfdf5df28414b715199a740f80b7f559bd558a3f0c0186e60149ee86620
+  (B root: 65492c0681df09eb403160136bb648de17f67bd8efc441467c0fc23b8d2950e9
+    (L root: aa86be763e41db7eaae266afc79ab46d02343c5d3b05da171d351afbd25c1525)
+    (L root: 05e3bc756e005c1bc5e4daf8a3da95d435af52476b0a0e6d52e719a2b1e3434a))
+  (B root: 3ae3330dcf932104d42b75b4da386896a628926f411737b34430fa65e526824d
+    (L root: 4cc9e99389b5f729cbef6fe79e97a6f562841a2852e25e508e3bd06ce0de9c26)
+    (L root: 4cc9e99389b5f729cbef6fe79e97a6f562841a2852e25e508e3bd06ce0de9c26)))
+
+*/
+```
+
+### Audit Proof
+
+```go
+
+blocks := [][]byte{
+    []byte("alpha"),
+    []byte("beta"),
+    []byte("kappa"),
+    []byte("gamma"),
+    []byte("epsilon"),
+    []byte("omega"),
+    []byte("mu"),
+    []byte("zeta"),
+}
+
+tree := NewTree(IdentityHashForTest, blocks)
+checksum := treeA.checksumFunc([]byte("omega"))
+
+// for printing checksums
+f := func(xs []byte) string {
+    return string(xs)
+}
+
+fmt.Println(tree.GetProofString(tree.root.GetChecksum(), checksum, f))
+
+/*
+
+output:
+
+epsilon + omega = epsilonomega
+epsilonomega + muzeta = epsilonomegamuzeta
+alphabetakappagamma + epsilonomegamuzeta = alphabetakappagammaepsilonomegamuzeta
+
+*/
+```
+
+[1]: https://www.codeproject.com/Articles/1176140/Understanding-Merkle-Trees-Why-use-them-who-uses-t

hashing.go

@@ -0,0 +1,14 @@
+package merkletree
+
+import "crypto/sha256"
+
+func Sha256DoubleHash(data []byte) []byte {
+	first := sha256.Sum256(data)
+	secnd := sha256.Sum256(first[:])
+
+	return secnd[:]
+}
+
+func IdentityHashForTest(strbytes []byte) []byte {
+	return strbytes
+}