This is a Python port of merkle-tools.
Tools for creating Merkle trees, generating merkle proofs, and verification of merkle proofs.
import merkletools
mt = MerkleTools(hash_function=hashlib.sha512) # default is sha256
Adds a value as a leaf or a list of leafs to the tree. All values are hashed prior to being added to the tree.
list_data = ['Some text data', 'perhaps']
mt.add_leaf(list_data, True)
Returns the number of leaves that are currently added to the tree.
leaf_count = mt.get_leaf_count();
Returns the value of the leaf at the given index as a hex string.
leaf_value = mt.get_leaf(1)
Generates the merkle tree using the leaves that have been added.
mt.make_tree();
.is_ready
is a boolean property indicating if the tree is built and ready to supply its root and proofs. The is_ready
state is True
only after calling 'make_tree()'. Adding leaves or resetting the tree will change the ready state to False.
is_ready = mt.is_ready
Returns the merkle root of the tree as a hex string. If the tree is not ready, None
is returned.
root_value = mt.get_merkle_root();
Returns the proof as an array of hash objects for the leaf at the given index. If the tree is not ready or no leaf exists at the given index, null is returned.
proof = mt.get_proof(1)
The proof array contains a set of merkle sibling objects. Each object contains the sibling hash, with the key value of either right or left. The right or left value tells you where that sibling was in relation to the current hash being evaluated. This information is needed for proof validation, as explained in the following section.
Returns a boolean indicating whether or not the proof is valid and correctly connects the target_hash
to the merkle_root
. proof
is a proof array as supplied by the get_proof
method. The target_hash
and merkle_root
parameters must be a hex strings.
proof = [
{ r: '09096dbc49b7909917e13b795ebf289ace50b870440f10424af8845fb7761ea5' },
{ r: 'ed2456914e48c1e17b7bd922177291ef8b7f553edf1b1f66b6fc1a076524b22f' },
{ l: 'eac53dde9661daf47a428efea28c81a021c06d64f98eeabbdcff442d992153a8' },
]
target_hash = '36e0fd847d927d68475f32a94efff30812ee3ce87c7752973f4dd7476aa2e97e'
merkle_root = 'b8b1f39aa2e3fc2dde37f3df04e829f514fb98369b522bfb35c663befa896766'
is_valid = mt.validate_proof(proof, targetHash, merkleRoot)
The proof process uses all the proof objects in the array to attempt to prove a relationship between the target_hash
and the merkle_root
values. The steps to validate a proof are:
- Concatenate
target_hash
and the first hash in the proof array. The right or left designation specifies which side of the concatenation that the proof hash value should be on. - Hash the resulting value.
- Concatenate the resulting hash with the next hash in the proof array, using the same left and right rules.
- Hash that value and continue the process until you’ve gone through each item in the proof array.
- The final hash value should equal the
merkle_root
value if the proof is valid, otherwise the proof is invalid.
mt = MerkleTools()
mt.add_leaf("tierion", True)
mt.add_leaf(["bitcoin", "blockchain"], True)
mt.make_tree()
print "root:", mt.get_merkle_root() # root: '765f15d171871b00034ee55e48ffdf76afbc44ed0bcff5c82f31351d333c2ed1'
print mt.get_proof(1) # [{l: '2da7240f6c88536be72abe9f04e454c6478ee29709fc3729ddfb942f804fbf08'},
# {r: 'ef7797e13d3a75526946a3bcf00daec9fc9c9c4d51ddc7cc5df888f74dd434d1'}]
print mt.validate_proof(mt.get_proof(1), mt.get_leaf(1), mt.get_merkle_root()) # True
-
Internally, leaves are stored as
bytes
. When the tree is built, it is generated by hashing together thebytes
values. -
Lonely leaf nodes are promoted to the next level up, as depicted below.
ROOT=Hash(H+E) / \ / \ H=Hash(F+G) E / \ \ / \ \ F=Hash(A+B) G=Hash(C+D) E / \ / \ \ / \ / \ \ A B C D E
This module uses Python's hashlib
for hashing. Inside a MerkleTools
object all
hashes are stored as Python bytes
. This way hashes can be concatenated simply with +
and the result
used as input for the hash function. But for
simplicity and easy to use MerkleTools
methods expect that both input and outputs are hex
strings. We can convert from one type to the other using default Python string methods.
For example:
hash = hashlib.sha256('a').digest() # '\xca\x97\x81\x12\xca\x1b\xbd\xca\xfa\xc21\xb3\x9a#\xdcM\xa7\x86\xef\xf8\x14|Nr\xb9\x80w\x85\xaf\xeeH\xbb'
hex_string = hash.hex() # 'ca978112ca1bbdcafac231b39a23dc4da786eff8147c4e72b9807785afee48bb'
back_to_hash = hex_string.decode('hex') # '\xca\x97\x81\x12\xca\x1b\xbd\xca\xfa\xc21\xb3\x9a#\xdcM\xa7\x86\xef\xf8\x14|Nr\xb9\x80w\x85\xaf\xeeH\xbb'