github.com/wealdtech/go-merkletree/v2
Package merkletree is an implementation of a Merkle tree (https://en.wikipedia.org/wiki/Merkle_tree). It provides methods to create a tree and generate and verify proofs. The hashing algorithm for the tree is selectable between BLAKE2b and Keccak256, or you can supply your own. This implementation includes advanced features salting and pollarding. Salting is the act of adding a piece of data to each value in the Merkle tree as it is initially hashed to form the leaves, which helps avoid rainbow table attacks on leaf hashes presented as part of proofs. Pollarding is the act of providing the root plus all branches to a certain height which can be used to reduce the size of proofs. This is useful when multiple proofs are presented against the same tree as it can reduce the overall size. Creating a Merkle tree requires a list of values that are each byte arrays. Once a tree has been created proofs can be generated using the tree's GenerateProof() function. The package includes a function VerifyProof() to verify a generated proof given only the data to prove, proof and the pollard of the relevant Merkle tree. This allows for efficient verification of proofs without requiring the entire Merkle tree to be stored or recreated. The tree pads its values to the next highest power of 2; values not supplied are treated as null with a value hash of 0. This can be seen graphically by generating a DOT representation of the graph with DOT(). If salting is enabled it appends an 4-byte value to each piece of data. The value is the binary representation of the index in big-endian form. Note that if there are more than 2^32 values in the tree the salt will wrap, being modulo 2^32 Package merkletree is an implementation of a Merkle tree (https://en.wikipedia.org/wiki/Merkle_tree). It provides methods to create a tree and generate and verify proofs. The hashing algorithm for the tree is selectable between BLAKE2b and Keccak256, or you can supply your own. This implementation includes advanced features salting and pollarding. Salting is the act of adding a piece of data to each value in the Merkle tree as it is initially hashed to form the leaves, which helps avoid rainbow table attacks on leaf hashes presented as part of proofs. Pollarding is the act of providing the root plus all branches to a certain height which can be used to reduce the size of proofs. This is useful when multiple proofs are presented against the same tree as it can reduce the overall size. Creating a Merkle tree requires a list of values that are each byte arrays. Once a tree has been created proofs can be generated using the tree's GenerateProof() function. The package includes a function VerifyProof() to verify a generated proof given only the data to prove, proof and the pollard of the relevant Merkle tree. This allows for efficient verification of proofs without requiring the entire Merkle tree to be stored or recreated. The tree pads its values to the next highest power of 2; values not supplied are treated as null with a value hash of 0. This can be seen graphically by generating a DOT representation of the graph with DOT(). If salting is enabled it appends an 4-byte value to each piece of data. The value is the binary representation of the index in big-endian form. Note that if there are more than 2^32 values in the tree the salt will wrap, being modulo 2^32
Readme
Go implementation of a Merkle tree.
go-merkletree is a standard Go module which can be installed with:
go get github.com/wealdtech/go-merkletree
go-merkletree generates Merkle trees from an array of []byte values and uses them to generate proofs. Proofs can be verified, and graphs generated
This package uses pollards and sparese multiproofs for efficient generation of multiple proofs against the same tree; see the articles Understanding Merkle pollards and Understanding sparse Merkle multiproofs for details.
This package can generate visualisations (in DOT format) for trees and proofs. Below is a tree visualisation:
and below is a proof visualisation with the value being proved in red, the intermediate branches in green and the root in blue:
package main
import (
merkletree "github.com/wealdtech/go-merkletree"
)
// Example using the Merkle tree to generate and verify proofs.
func main() {
// Data for the tree
data := [][]byte{
[]byte("Foo"),
[]byte("Bar"),
[]byte("Baz"),
}
// Create the tree
tree, err := merkletree.NewTree(merkletree.WithData(data))
if err != nil {
panic(err)
}
// Fetch the root hash of the tree
root := tree.Root()
baz := data[2]
// Generate a proof for 'Baz'
proof, err := tree.GenerateProof(baz, 0)
if err != nil {
panic(err)
}
// Verify the proof for 'Baz'
verified, err := merkletree.VerifyProof(baz, false, proof, [][]byte{root})
if err != nil {
panic(err)
}
if !verified {
panic("failed to verify proof for Baz")
}
}
Jim McDonald: @mcdee.
Contributions welcome. Please check out the issues.
Apache-2.0 © 2019 Weald Technology Trading Ltd
FAQs
Package merkletree is an implementation of a Merkle tree (https://en.wikipedia.org/wiki/Merkle_tree). It provides methods to create a tree and generate and verify proofs. The hashing algorithm for the tree is selectable between BLAKE2b and Keccak256, or you can supply your own. This implementation includes advanced features salting and pollarding. Salting is the act of adding a piece of data to each value in the Merkle tree as it is initially hashed to form the leaves, which helps avoid rainbow table attacks on leaf hashes presented as part of proofs. Pollarding is the act of providing the root plus all branches to a certain height which can be used to reduce the size of proofs. This is useful when multiple proofs are presented against the same tree as it can reduce the overall size. Creating a Merkle tree requires a list of values that are each byte arrays. Once a tree has been created proofs can be generated using the tree's GenerateProof() function. The package includes a function VerifyProof() to verify a generated proof given only the data to prove, proof and the pollard of the relevant Merkle tree. This allows for efficient verification of proofs without requiring the entire Merkle tree to be stored or recreated. The tree pads its values to the next highest power of 2; values not supplied are treated as null with a value hash of 0. This can be seen graphically by generating a DOT representation of the graph with DOT(). If salting is enabled it appends an 4-byte value to each piece of data. The value is the binary representation of the index in big-endian form. Note that if there are more than 2^32 values in the tree the salt will wrap, being modulo 2^32 Package merkletree is an implementation of a Merkle tree (https://en.wikipedia.org/wiki/Merkle_tree). It provides methods to create a tree and generate and verify proofs. The hashing algorithm for the tree is selectable between BLAKE2b and Keccak256, or you can supply your own. This implementation includes advanced features salting and pollarding. Salting is the act of adding a piece of data to each value in the Merkle tree as it is initially hashed to form the leaves, which helps avoid rainbow table attacks on leaf hashes presented as part of proofs. Pollarding is the act of providing the root plus all branches to a certain height which can be used to reduce the size of proofs. This is useful when multiple proofs are presented against the same tree as it can reduce the overall size. Creating a Merkle tree requires a list of values that are each byte arrays. Once a tree has been created proofs can be generated using the tree's GenerateProof() function. The package includes a function VerifyProof() to verify a generated proof given only the data to prove, proof and the pollard of the relevant Merkle tree. This allows for efficient verification of proofs without requiring the entire Merkle tree to be stored or recreated. The tree pads its values to the next highest power of 2; values not supplied are treated as null with a value hash of 0. This can be seen graphically by generating a DOT representation of the graph with DOT(). If salting is enabled it appends an 4-byte value to each piece of data. The value is the binary representation of the index in big-endian form. Note that if there are more than 2^32 values in the tree the salt will wrap, being modulo 2^32
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