merkle

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 Go to latest Published: May 30, 2019 License: Apache-2.0 Imports: 14 Imported by: 0

README

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.

Documentation

Overview

Package merkle 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.

Be aware that the current implementation by itself does not prevent second pre-image attacks. Hence, use this library with caution. Otherwise you might run into similar issues as, e.g., in early Bitcoin: https://bitcointalk.org/?topic=102395 

              *
             / \
           /     \
         /         \
       /             \
      *               *
     / \             / \
    /   \           /   \
   /     \         /     \
  *       *       *       h6
 / \     / \     / \
h0  h1  h2  h3  h4  h5

TODO(ismail): add 2nd pre-image protection or clarify further on how we use this and why this secure.

Index

Constants

View Source 
const (
	KeyEncodingURL keyEncoding = iota
	KeyEncodingHex
	KeyEncodingMax // Number of known encodings. Used for testing
)
View Source 
const ProofOpSimpleValue = "simple:v"

Variables

View Source 
var (
	ErrInvalidLengthMerkle = fmt.Errorf("proto: negative length found during unmarshaling")
	ErrIntOverflowMerkle   = fmt.Errorf("proto: integer overflow")
)

Functions

func KeyPathToKeys 

func KeyPathToKeys(path string) (keys [][]byte, err error)

Decode a path to a list of keys. Path must begin with `/`. Each key must use a known encoding.

func SimpleHashFromByteSlices 

func SimpleHashFromByteSlices(items [][]byte) []byte

SimpleHashFromByteSlices computes a Merkle tree where the leaves are the byte slice, in the provided order.

func SimpleHashFromByteSlicesIterative 

func SimpleHashFromByteSlicesIterative(input [][]byte) []byte

SimpleHashFromByteSliceIterative is an iterative alternative to SimpleHashFromByteSlice motivated by potential performance improvements. (#2611) had suggested that an iterative version of SimpleHashFromByteSlice would be faster, presumably because we can envision some overhead accumulating from stack frames and function calls. Additionally, a recursive algorithm risks hitting the stack limit and causing a stack overflow should the tree be too large.

Provided here is an iterative alternative, a simple test to assert correctness and a benchmark. On the performance side, there appears to be no overall difference:

BenchmarkSimpleHashAlternatives/recursive-4 20000 77677 ns/op BenchmarkSimpleHashAlternatives/iterative-4 20000 76802 ns/op

On the surface it might seem that the additional overhead is due to the different allocation patterns of the implementations. The recursive version uses a single [][]byte slices which it then re-slices at each level of the tree. The iterative version reproduces [][]byte once within the function and then rewrites sub-slices of that array at each level of the tree.

Experimenting by modifying the code to simply calculate the hash and not store the result show little to no difference in performance.

These preliminary results suggest:

  1. The performance of the SimpleHashFromByteSlice is pretty good
  2. Go has low overhead for recursive functions
  3. The performance of the SimpleHashFromByteSlice routine is dominated by the actual hashing of data

Although this work is in no way exhaustive, point #3 suggests that optimization of this routine would need to take an alternative approach to make significant improvements on the current performance.

Finally, considering that the recursive implementation is easier to read, it might not be worthwhile to switch to a less intuitive implementation for so little benefit.

func SimpleHashFromMap 

func SimpleHashFromMap(m map[string][]byte) []byte

SimpleHashFromMap computes a Merkle tree from sorted map. Like calling SimpleHashFromHashers with `item = []byte(Hash(key) | Hash(value))`, sorted by `item`.

func SimpleProofsFromMap 

func SimpleProofsFromMap(m map[string][]byte) (rootHash []byte, proofs map[string]*SimpleProof, keys []string)

SimpleProofsFromMap generates proofs from a map. The keys/values of the map will be used as the keys/values in the underlying key-value pairs. The keys are sorted before the proofs are computed.

Types

type KVPair 

type KVPair cmn.KVPair

A local extension to KVPair that can be hashed. Key and value are length prefixed and concatenated, then hashed.

func (KVPair) Bytes 

func (kv KVPair) Bytes() []byte

Bytes returns key || value, with both the key and value length prefixed.

type Key 

type Key struct {
	// contains filtered or unexported fields
}

type KeyPath 

type KeyPath []Key

func (KeyPath) AppendKey 

func (pth KeyPath) AppendKey(key []byte, enc keyEncoding) KeyPath

func (KeyPath) String 

func (pth KeyPath) String() string

type OpDecoder 

type OpDecoder func(ProofOp) (ProofOperator, error)

type Proof 

type Proof struct {
	Ops                  []ProofOp `protobuf:"bytes,1,rep,name=ops" json:"ops"`
	XXX_NoUnkeyedLiteral struct{}  `json:"-"`
	XXX_unrecognized     []byte    `json:"-"`
	XXX_sizecache        int32     `json:"-"`
}

Proof is Merkle proof defined by the list of ProofOps

func NewPopulatedProof 

func NewPopulatedProof(r randyMerkle, easy bool) *Proof

func (*Proof) Descriptor 

func (*Proof) Descriptor() ([]byte, []int)

func (*Proof) Equal 

func (this *Proof) Equal(that interface{}) bool

func (*Proof) GetOps 

func (m *Proof) GetOps() []ProofOp

func (*Proof) Marshal 

func (m *Proof) Marshal() (dAtA []byte, err error)

func (*Proof) MarshalTo 

func (m *Proof) MarshalTo(dAtA []byte) (int, error)

func (*Proof) ProtoMessage 

func (*Proof) ProtoMessage()

func (*Proof) Reset 

func (m *Proof) Reset()

func (*Proof) Size 

func (m *Proof) Size() (n int)

func (*Proof) String 

func (m *Proof) String() string

func (*Proof) Unmarshal 

func (m *Proof) Unmarshal(dAtA []byte) error

func (*Proof) XXX_DiscardUnknown 

func (m *Proof) XXX_DiscardUnknown()

func (*Proof) XXX_Marshal 

func (m *Proof) XXX_Marshal(b []byte, deterministic bool) ([]byte, error)

func (*Proof) XXX_Merge 

func (dst *Proof) XXX_Merge(src proto.Message)

func (*Proof) XXX_Size 

func (m *Proof) XXX_Size() int

func (*Proof) XXX_Unmarshal 

func (m *Proof) XXX_Unmarshal(b []byte) error

type ProofOp 

type ProofOp struct {
	Type                 string   `protobuf:"bytes,1,opt,name=type,proto3" json:"type,omitempty"`
	Key                  []byte   `protobuf:"bytes,2,opt,name=key,proto3" json:"key,omitempty"`
	Data                 []byte   `protobuf:"bytes,3,opt,name=data,proto3" json:"data,omitempty"`
	XXX_NoUnkeyedLiteral struct{} `json:"-"`
	XXX_unrecognized     []byte   `json:"-"`
	XXX_sizecache        int32    `json:"-"`
}

ProofOp defines an operation used for calculating Merkle root The data could be arbitrary format, providing nessecary data for example neighbouring node hash

func NewPopulatedProofOp 

func NewPopulatedProofOp(r randyMerkle, easy bool) *ProofOp

func (*ProofOp) Descriptor 

func (*ProofOp) Descriptor() ([]byte, []int)

func (*ProofOp) Equal 

func (this *ProofOp) Equal(that interface{}) bool

func (*ProofOp) GetData 

func (m *ProofOp) GetData() []byte

func (*ProofOp) GetKey 

func (m *ProofOp) GetKey() []byte

func (*ProofOp) GetType 

func (m *ProofOp) GetType() string

func (*ProofOp) Marshal 

func (m *ProofOp) Marshal() (dAtA []byte, err error)

func (*ProofOp) MarshalTo 

func (m *ProofOp) MarshalTo(dAtA []byte) (int, error)

func (*ProofOp) ProtoMessage 

func (*ProofOp) ProtoMessage()

func (*ProofOp) Reset 

func (m *ProofOp) Reset()

func (*ProofOp) Size 

func (m *ProofOp) Size() (n int)

func (*ProofOp) String 

func (m *ProofOp) String() string

func (*ProofOp) Unmarshal 

func (m *ProofOp) Unmarshal(dAtA []byte) error

func (*ProofOp) XXX_DiscardUnknown 

func (m *ProofOp) XXX_DiscardUnknown()

func (*ProofOp) XXX_Marshal 

func (m *ProofOp) XXX_Marshal(b []byte, deterministic bool) ([]byte, error)

func (*ProofOp) XXX_Merge 

func (dst *ProofOp) XXX_Merge(src proto.Message)

func (*ProofOp) XXX_Size 

func (m *ProofOp) XXX_Size() int

func (*ProofOp) XXX_Unmarshal 

func (m *ProofOp) XXX_Unmarshal(b []byte) error

type ProofOperator 

type ProofOperator interface {
	Run([][]byte) ([][]byte, error)
	GetKey() []byte
	ProofOp() ProofOp
}

ProofOperator is a layer for calculating intermediate Merkle roots when a series of Merkle trees are chained together. Run() takes leaf values from a tree and returns the Merkle root for the corresponding tree. It takes and returns a list of bytes to allow multiple leaves to be part of a single proof, for instance in a range proof. ProofOp() encodes the ProofOperator in a generic way so it can later be decoded with OpDecoder.

func SimpleValueOpDecoder 

func SimpleValueOpDecoder(pop ProofOp) (ProofOperator, error)

type ProofOperators 

type ProofOperators []ProofOperator

ProofOperators is a slice of ProofOperator(s). Each operator will be applied to the input value sequentially and the last Merkle root will be verified with already known data

func (ProofOperators) Verify 

func (poz ProofOperators) Verify(root []byte, keypath string, args [][]byte) (err error)

func (ProofOperators) VerifyValue 

func (poz ProofOperators) VerifyValue(root []byte, keypath string, value []byte) (err error)

type ProofRuntime 

type ProofRuntime struct {
	// contains filtered or unexported fields
}

func DefaultProofRuntime 

func DefaultProofRuntime() (prt *ProofRuntime)

DefaultProofRuntime only knows about Simple value proofs. To use e.g. IAVL proofs, register op-decoders as defined in the IAVL package.

func NewProofRuntime 

func NewProofRuntime() *ProofRuntime

func (*ProofRuntime) Decode 

func (prt *ProofRuntime) Decode(pop ProofOp) (ProofOperator, error)

func (*ProofRuntime) DecodeProof 

func (prt *ProofRuntime) DecodeProof(proof *Proof) (ProofOperators, error)

func (*ProofRuntime) RegisterOpDecoder 

func (prt *ProofRuntime) RegisterOpDecoder(typ string, dec OpDecoder)

func (*ProofRuntime) Verify 

func (prt *ProofRuntime) Verify(proof *Proof, root []byte, keypath string, args [][]byte) (err error)

func (*ProofRuntime) VerifyAbsence 

func (prt *ProofRuntime) VerifyAbsence(proof *Proof, root []byte, keypath string) (err error)

TODO In the long run we'll need a method of classifcation of ops, whether existence or absence or perhaps a third?

func (*ProofRuntime) VerifyValue 

func (prt *ProofRuntime) VerifyValue(proof *Proof, root []byte, keypath string, value []byte) (err error)

type SimpleProof 

type SimpleProof struct {
	Total    int      `json:"total"`     // Total number of items.
	Index    int      `json:"index"`     // Index of item to prove.
	LeafHash []byte   `json:"leaf_hash"` // Hash of item value.
	Aunts    [][]byte `json:"aunts"`     // Hashes from leaf's sibling to a root's child.
}

SimpleProof represents a simple Merkle proof. NOTE: The convention for proofs is to include leaf hashes but to exclude the root hash. This convention is implemented across IAVL range proofs as well. Keep this consistent unless there's a very good reason to change everything. This also affects the generalized proof system as well.

func SimpleProofsFromByteSlices 

func SimpleProofsFromByteSlices(items [][]byte) (rootHash []byte, proofs []*SimpleProof)

SimpleProofsFromByteSlices computes inclusion proof for given items. proofs[0] is the proof for items[0].

func (*SimpleProof) ComputeRootHash 

func (sp *SimpleProof) ComputeRootHash() []byte

Compute the root hash given a leaf hash. Does not verify the result.

func (*SimpleProof) String 

func (sp *SimpleProof) String() string

String implements the stringer interface for SimpleProof. It is a wrapper around StringIndented.

func (*SimpleProof) StringIndented 

func (sp *SimpleProof) StringIndented(indent string) string

StringIndented generates a canonical string representation of a SimpleProof.

func (*SimpleProof) Verify 

func (sp *SimpleProof) Verify(rootHash []byte, leaf []byte) error

Verify that the SimpleProof proves the root hash. Check sp.Index/sp.Total manually if needed

type SimpleProofNode 

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)
}

SimpleProofNode is a 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.

func (*SimpleProofNode) FlattenAunts 

func (spn *SimpleProofNode) FlattenAunts() [][]byte

FlattenAunts will return the inner hashes for the item corresponding to the leaf, starting from a leaf SimpleProofNode.

type SimpleValueOp 

type SimpleValueOp struct {

	// To encode in ProofOp.Data
	Proof *SimpleProof `json:"simple_proof"`
	// contains filtered or unexported fields
}

SimpleValueOp takes a key and a single value as argument and produces the root hash. The corresponding tree structure is the SimpleMap tree. SimpleMap takes a Hasher, and currently Tendermint uses aminoHasher. SimpleValueOp should support the hash function as used in aminoHasher. TODO support additional hash functions here as options/args to this operator.

If the produced root hash matches the expected hash, the proof is good.

func NewSimpleValueOp 

func NewSimpleValueOp(key []byte, proof *SimpleProof) SimpleValueOp

func (SimpleValueOp) GetKey 

func (op SimpleValueOp) GetKey() []byte

func (SimpleValueOp) ProofOp 

func (op SimpleValueOp) ProofOp() ProofOp

func (SimpleValueOp) Run 

func (op SimpleValueOp) Run(args [][]byte) ([][]byte, error)

func (SimpleValueOp) String 

func (op SimpleValueOp) String() string

type Tree 

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)
}

Tree is a Merkle tree interface.

Source Files

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