Merkle staticmethods
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Jack Robison
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84908ec8ec
commit
23035b9aa0
1 changed files with 41 additions and 36 deletions
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@ -43,10 +43,12 @@ class Merkle:
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def __init__(self, hash_func=double_sha256):
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self.hash_func = hash_func
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def tree_depth(self, hash_count):
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return self.branch_length(hash_count) + 1
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@staticmethod
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def tree_depth(hash_count):
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return Merkle.branch_length(hash_count) + 1
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def branch_length(self, hash_count):
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@staticmethod
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def branch_length(hash_count):
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"""Return the length of a merkle branch given the number of hashes."""
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if not isinstance(hash_count, int):
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raise TypeError('hash_count must be an integer')
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@ -54,7 +56,8 @@ class Merkle:
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raise ValueError('hash_count must be at least 1')
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return ceil(log(hash_count, 2))
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def branch_and_root(self, hashes, index, length=None):
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@staticmethod
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def branch_and_root(hashes, index, length=None, hash_func=double_sha256):
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"""Return a (merkle branch, merkle_root) pair given hashes, and the
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index of one of those hashes.
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"""
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@ -64,7 +67,7 @@ class Merkle:
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# This also asserts hashes is not empty
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if not 0 <= index < len(hashes):
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raise ValueError(f"index '{index}/{len(hashes)}' out of range")
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natural_length = self.branch_length(len(hashes))
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natural_length = Merkle.branch_length(len(hashes))
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if length is None:
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length = natural_length
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else:
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@ -73,7 +76,6 @@ class Merkle:
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if length < natural_length:
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raise ValueError('length out of range')
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hash_func = self.hash_func
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branch = []
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for _ in range(length):
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if len(hashes) & 1:
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@ -85,44 +87,47 @@ class Merkle:
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return branch, hashes[0]
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def root(self, hashes, length=None):
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@staticmethod
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def root(hashes, length=None):
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"""Return the merkle root of a non-empty iterable of binary hashes."""
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branch, root = self.branch_and_root(hashes, 0, length)
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branch, root = Merkle.branch_and_root(hashes, 0, length)
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return root
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def root_from_proof(self, hash, branch, index):
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"""Return the merkle root given a hash, a merkle branch to it, and
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its index in the hashes array.
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# @staticmethod
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# def root_from_proof(hash, branch, index, hash_func=double_sha256):
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# """Return the merkle root given a hash, a merkle branch to it, and
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# its index in the hashes array.
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#
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# branch is an iterable sorted deepest to shallowest. If the
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# returned root is the expected value then the merkle proof is
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# verified.
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#
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# The caller should have confirmed the length of the branch with
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# branch_length(). Unfortunately this is not easily done for
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# bitcoin transactions as the number of transactions in a block
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# is unknown to an SPV client.
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# """
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# for elt in branch:
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# if index & 1:
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# hash = hash_func(elt + hash)
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# else:
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# hash = hash_func(hash + elt)
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# index >>= 1
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# if index:
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# raise ValueError('index out of range for branch')
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# return hash
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branch is an iterable sorted deepest to shallowest. If the
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returned root is the expected value then the merkle proof is
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verified.
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The caller should have confirmed the length of the branch with
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branch_length(). Unfortunately this is not easily done for
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bitcoin transactions as the number of transactions in a block
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is unknown to an SPV client.
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"""
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hash_func = self.hash_func
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for elt in branch:
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if index & 1:
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hash = hash_func(elt + hash)
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else:
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hash = hash_func(hash + elt)
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index >>= 1
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if index:
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raise ValueError('index out of range for branch')
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return hash
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def level(self, hashes, depth_higher):
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@staticmethod
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def level(hashes, depth_higher):
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"""Return a level of the merkle tree of hashes the given depth
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higher than the bottom row of the original tree."""
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size = 1 << depth_higher
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root = self.root
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root = Merkle.root
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return [root(hashes[n: n + size], depth_higher)
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for n in range(0, len(hashes), size)]
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def branch_and_root_from_level(self, level, leaf_hashes, index,
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@staticmethod
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def branch_and_root_from_level(level, leaf_hashes, index,
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depth_higher):
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"""Return a (merkle branch, merkle_root) pair when a merkle-tree has a
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level cached.
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@ -146,10 +151,10 @@ class Merkle:
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if not isinstance(leaf_hashes, list):
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raise TypeError("leaf_hashes must be a list")
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leaf_index = (index >> depth_higher) << depth_higher
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leaf_branch, leaf_root = self.branch_and_root(
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leaf_branch, leaf_root = Merkle.branch_and_root(
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leaf_hashes, index - leaf_index, depth_higher)
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index >>= depth_higher
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level_branch, root = self.branch_and_root(level, index)
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level_branch, root = Merkle.branch_and_root(level, index)
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# Check last so that we know index is in-range
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if leaf_root != level[index]:
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raise ValueError('leaf hashes inconsistent with level')
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