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simple merkle tree

pull/1842/head
Ethan Buchman 8 years ago
parent
commit
fd296811df
4 changed files with 391 additions and 0 deletions
  1. +4
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      merkle/README.md
  2. +277
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      merkle/simple_tree.go
  3. +87
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      merkle/simple_tree_test.go
  4. +23
    -0
      merkle/types.go

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merkle/README.md View File

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## Simple Merkle Tree
For smaller static data structures that don't require immutable snapshots or mutability;
for instance the transactions and validation signatures of a block can be hashed using this simple merkle tree logic.

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merkle/simple_tree.go View File

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/*
Computes a deterministic minimal height merkle tree hash.
If the number of items is not a power of two, some leaves
will be at different levels. Tries to keep both sides of
the tree the same size, but the left may be one greater.
Use this for short deterministic trees, such as the validator list.
For larger datasets, use IAVLTree.
*
/ \
/ \
/ \
/ \
* *
/ \ / \
/ \ / \
/ \ / \
* * * h6
/ \ / \ / \
h0 h1 h2 h3 h4 h5
*/
package merkle
import (
"bytes"
"fmt"
"sort"
"golang.org/x/crypto/ripemd160"
. "github.com/tendermint/go-common"
"github.com/tendermint/go-wire"
)
func SimpleHashFromTwoHashes(left []byte, right []byte) []byte {
var n int
var err error
var hasher = ripemd160.New()
wire.WriteByteSlice(left, hasher, &n, &err)
wire.WriteByteSlice(right, hasher, &n, &err)
if err != nil {
PanicCrisis(err)
}
return hasher.Sum(nil)
}
func SimpleHashFromHashes(hashes [][]byte) []byte {
// Recursive impl.
switch len(hashes) {
case 0:
return nil
case 1:
return hashes[0]
default:
left := SimpleHashFromHashes(hashes[:(len(hashes)+1)/2])
right := SimpleHashFromHashes(hashes[(len(hashes)+1)/2:])
return SimpleHashFromTwoHashes(left, right)
}
}
// Convenience for SimpleHashFromHashes.
func SimpleHashFromBinaries(items []interface{}) []byte {
hashes := make([][]byte, len(items))
for i, item := range items {
hashes[i] = SimpleHashFromBinary(item)
}
return SimpleHashFromHashes(hashes)
}
// General Convenience
func SimpleHashFromBinary(item interface{}) []byte {
hasher, n, err := ripemd160.New(), new(int), new(error)
wire.WriteBinary(item, hasher, n, err)
if *err != nil {
PanicCrisis(err)
}
return hasher.Sum(nil)
}
// Convenience for SimpleHashFromHashes.
func SimpleHashFromHashables(items []Hashable) []byte {
hashes := make([][]byte, len(items))
for i, item := range items {
hash := item.Hash()
hashes[i] = hash
}
return SimpleHashFromHashes(hashes)
}
// Convenience for SimpleHashFromHashes.
func SimpleHashFromMap(m map[string]interface{}) []byte {
kpPairsH := MakeSortedKVPairs(m)
return SimpleHashFromHashables(kpPairsH)
}
//--------------------------------------------------------------------------------
/* Convenience struct for key-value pairs.
A list of KVPairs is hashed via `SimpleHashFromHashables`.
NOTE: Each `Value` is encoded for hashing without extra type information,
so the user is presumed to be aware of the Value types.
*/
type KVPair struct {
Key string
Value interface{}
}
func (kv KVPair) Hash() []byte {
hasher, n, err := ripemd160.New(), new(int), new(error)
wire.WriteString(kv.Key, hasher, n, err)
if kvH, ok := kv.Value.(Hashable); ok {
wire.WriteByteSlice(kvH.Hash(), hasher, n, err)
} else {
wire.WriteBinary(kv.Value, hasher, n, err)
}
if *err != nil {
PanicSanity(*err)
}
return hasher.Sum(nil)
}
type KVPairs []KVPair
func (kvps KVPairs) Len() int { return len(kvps) }
func (kvps KVPairs) Less(i, j int) bool { return kvps[i].Key < kvps[j].Key }
func (kvps KVPairs) Swap(i, j int) { kvps[i], kvps[j] = kvps[j], kvps[i] }
func (kvps KVPairs) Sort() { sort.Sort(kvps) }
func MakeSortedKVPairs(m map[string]interface{}) []Hashable {
kvPairs := []KVPair{}
for k, v := range m {
kvPairs = append(kvPairs, KVPair{k, v})
}
KVPairs(kvPairs).Sort()
kvPairsH := []Hashable{}
for _, kvp := range kvPairs {
kvPairsH = append(kvPairsH, kvp)
}
return kvPairsH
}
//--------------------------------------------------------------------------------
type SimpleProof struct {
Aunts [][]byte `json:"aunts"` // Hashes from leaf's sibling to a root's child.
}
// proofs[0] is the proof for items[0].
func SimpleProofsFromHashables(items []Hashable) (rootHash []byte, proofs []*SimpleProof) {
trails, rootSPN := trailsFromHashables(items)
rootHash = rootSPN.Hash
proofs = make([]*SimpleProof, len(items))
for i, trail := range trails {
proofs[i] = &SimpleProof{
Aunts: trail.FlattenAunts(),
}
}
return
}
// Verify that leafHash is a leaf hash of the simple-merkle-tree
// which hashes to rootHash.
func (sp *SimpleProof) Verify(index int, total int, leafHash []byte, rootHash []byte) bool {
computedHash := computeHashFromAunts(index, total, leafHash, sp.Aunts)
if computedHash == nil {
return false
}
if !bytes.Equal(computedHash, rootHash) {
return false
}
return true
}
func (sp *SimpleProof) String() string {
return sp.StringIndented("")
}
func (sp *SimpleProof) StringIndented(indent string) string {
return fmt.Sprintf(`SimpleProof{
%s Aunts: %X
%s}`,
indent, sp.Aunts,
indent)
}
// Use the leafHash and innerHashes to get the root merkle hash.
// If the length of the innerHashes slice isn't exactly correct, the result is nil.
func computeHashFromAunts(index int, total int, leafHash []byte, innerHashes [][]byte) []byte {
// Recursive impl.
if index >= total {
return nil
}
switch total {
case 0:
PanicSanity("Cannot call computeHashFromAunts() with 0 total")
return nil
case 1:
if len(innerHashes) != 0 {
return nil
}
return leafHash
default:
if len(innerHashes) == 0 {
return nil
}
numLeft := (total + 1) / 2
if index < numLeft {
leftHash := computeHashFromAunts(index, numLeft, leafHash, innerHashes[:len(innerHashes)-1])
if leftHash == nil {
return nil
}
return SimpleHashFromTwoHashes(leftHash, innerHashes[len(innerHashes)-1])
} else {
rightHash := computeHashFromAunts(index-numLeft, total-numLeft, leafHash, innerHashes[:len(innerHashes)-1])
if rightHash == nil {
return nil
}
return SimpleHashFromTwoHashes(innerHashes[len(innerHashes)-1], rightHash)
}
}
}
// Helper structure to construct merkle proof.
// The node and the tree is thrown away afterwards.
// Exactly one of node.Left and node.Right is nil, unless node is the root, in which case both are nil.
// node.Parent.Hash = hash(node.Hash, node.Right.Hash) or
// hash(node.Left.Hash, node.Hash), depending on whether node is a left/right child.
type SimpleProofNode struct {
Hash []byte
Parent *SimpleProofNode
Left *SimpleProofNode // Left sibling (only one of Left,Right is set)
Right *SimpleProofNode // Right sibling (only one of Left,Right is set)
}
// Starting from a leaf SimpleProofNode, FlattenAunts() will return
// the inner hashes for the item corresponding to the leaf.
func (spn *SimpleProofNode) FlattenAunts() [][]byte {
// Nonrecursive impl.
innerHashes := [][]byte{}
for spn != nil {
if spn.Left != nil {
innerHashes = append(innerHashes, spn.Left.Hash)
} else if spn.Right != nil {
innerHashes = append(innerHashes, spn.Right.Hash)
} else {
break
}
spn = spn.Parent
}
return innerHashes
}
// trails[0].Hash is the leaf hash for items[0].
// trails[i].Parent.Parent....Parent == root for all i.
func trailsFromHashables(items []Hashable) (trails []*SimpleProofNode, root *SimpleProofNode) {
// Recursive impl.
switch len(items) {
case 0:
return nil, nil
case 1:
trail := &SimpleProofNode{items[0].Hash(), nil, nil, nil}
return []*SimpleProofNode{trail}, trail
default:
lefts, leftRoot := trailsFromHashables(items[:(len(items)+1)/2])
rights, rightRoot := trailsFromHashables(items[(len(items)+1)/2:])
rootHash := SimpleHashFromTwoHashes(leftRoot.Hash, rightRoot.Hash)
root := &SimpleProofNode{rootHash, nil, nil, nil}
leftRoot.Parent = root
leftRoot.Right = rightRoot
rightRoot.Parent = root
rightRoot.Left = leftRoot
return append(lefts, rights...), root
}
}

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merkle/simple_tree_test.go View File

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package merkle
import (
"bytes"
. "github.com/tendermint/go-common"
. "github.com/tendermint/go-common/test"
"testing"
)
type testItem []byte
func (tI testItem) Hash() []byte {
return []byte(tI)
}
func TestSimpleProof(t *testing.T) {
total := 100
items := make([]Hashable, total)
for i := 0; i < total; i++ {
items[i] = testItem(RandBytes(32))
}
rootHash := SimpleHashFromHashables(items)
rootHash2, proofs := SimpleProofsFromHashables(items)
if !bytes.Equal(rootHash, rootHash2) {
t.Errorf("Unmatched root hashes: %X vs %X", rootHash, rootHash2)
}
// For each item, check the trail.
for i, item := range items {
itemHash := item.Hash()
proof := proofs[i]
// Verify success
ok := proof.Verify(i, total, itemHash, rootHash)
if !ok {
t.Errorf("Verification failed for index %v.", i)
}
// Wrong item index should make it fail
{
ok = proof.Verify((i+1)%total, total, itemHash, rootHash)
if ok {
t.Errorf("Expected verification to fail for wrong index %v.", i)
}
}
// Trail too long should make it fail
origAunts := proof.Aunts
proof.Aunts = append(proof.Aunts, RandBytes(32))
{
ok = proof.Verify(i, total, itemHash, rootHash)
if ok {
t.Errorf("Expected verification to fail for wrong trail length.")
}
}
proof.Aunts = origAunts
// Trail too short should make it fail
proof.Aunts = proof.Aunts[0 : len(proof.Aunts)-1]
{
ok = proof.Verify(i, total, itemHash, rootHash)
if ok {
t.Errorf("Expected verification to fail for wrong trail length.")
}
}
proof.Aunts = origAunts
// Mutating the itemHash should make it fail.
ok = proof.Verify(i, total, MutateByteSlice(itemHash), rootHash)
if ok {
t.Errorf("Expected verification to fail for mutated leaf hash")
}
// Mutating the rootHash should make it fail.
ok = proof.Verify(i, total, itemHash, MutateByteSlice(rootHash))
if ok {
t.Errorf("Expected verification to fail for mutated root hash")
}
}
}

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merkle/types.go View File

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package merkle
type Tree interface {
Size() (size int)
Height() (height int8)
Has(key []byte) (has bool)
Proof(key []byte) (value []byte, proof []byte, exists bool) // TODO make it return an index
Get(key []byte) (index int, value []byte, exists bool)
GetByIndex(index int) (key []byte, value []byte)
Set(key []byte, value []byte) (updated bool)
Remove(key []byte) (value []byte, removed bool)
HashWithCount() (hash []byte, count int)
Hash() (hash []byte)
Save() (hash []byte)
Load(hash []byte)
Copy() Tree
Iterate(func(key []byte, value []byte) (stop bool)) (stopped bool)
IterateRange(start []byte, end []byte, ascending bool, fx func(key []byte, value []byte) (stop bool)) (stopped bool)
}
type Hashable interface {
Hash() []byte
}

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