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#!/usr/bin/env python3
"""Verify a Bitflash UTXO inclusion proof against a UTXO root."""
import argparse
import hashlib
import json
import sys
from pathlib import Path
import bitflash_chain as chain
SCHEMA = "bitflash-utxo-inclusion-proof-1"
def canonical_bytes(obj):
return (json.dumps(obj, sort_keys=True, separators=(",", ":"), ensure_ascii=True) + "\n").encode("ascii")
def load_proof(path):
try:
return json.loads(Path(path).read_text(encoding="ascii"))
except Exception as e:
raise SystemExit("could not read proof: %s" % e)
def verify(proof, expected_root=None):
failures = []
if proof.get("schema") != SCHEMA:
failures.append("unexpected schema")
commitment = proof.get("commitment", {})
if commitment.get("algorithm") != "sorted-outpoint-merkle-sha256":
failures.append("unexpected commitment algorithm")
if commitment.get("leaf_domain") != chain.UTXO_LEAF_DOMAIN:
failures.append("unexpected leaf domain")
if commitment.get("node_domain") != chain.UTXO_NODE_DOMAIN_TAG:
failures.append("unexpected node domain")
target = proof.get("target", {})
outpoint = target.get("outpoint", "")
utxo = target.get("utxo", {})
if outpoint != "%s:%s" % (target.get("txid"), target.get("vout")):
failures.append("target outpoint does not match txid:vout")
try:
current = chain.utxo_leaf_hash(outpoint, utxo)
leaf_ok = target.get("leaf_hash") == current.hex()
except Exception as e:
failures.append("could not hash target leaf: %s" % e)
current = b"\x00" * 32
leaf_ok = False
if not leaf_ok:
failures.append("target leaf hash mismatch")
for i, step in enumerate(proof.get("proof", [])):
try:
sibling = bytes.fromhex(step["hash"])
except Exception:
failures.append("bad sibling hash at proof level %d" % i)
sibling = b"\x00" * 32
if len(sibling) != 32:
failures.append("bad sibling hash length at proof level %d" % i)
side = step.get("side")
if side == "right":
current = chain.sha256(chain.UTXO_NODE_DOMAIN + current + sibling)
elif side == "left":
current = chain.sha256(chain.UTXO_NODE_DOMAIN + sibling + current)
else:
failures.append("bad sibling side at proof level %d" % i)
computed_root = current.hex()
root = expected_root or commitment.get("root")
if computed_root != root:
failures.append("computed root does not match expected root")
return {
"schema": "bitflash-utxo-proof-verification-1",
"deterministic": True,
"target": {
"outpoint": outpoint,
"value_satoshis": utxo.get("value_satoshis"),
"value_btf": utxo.get("value_btf"),
"created_height": utxo.get("created_height"),
},
"commitment": {
"expected_root": root,
"computed_root": computed_root,
"leaf_hash": target.get("leaf_hash"),
"path_length": len(proof.get("proof", [])),
},
"checks": {
"schema_is_supported": proof.get("schema") == SCHEMA,
"leaf_hash_matches_target": leaf_ok,
"root_matches": computed_root == root,
},
"failures": failures,
"verdict": "UTXO_PROOF_VERIFIED" if not failures else "UTXO_PROOF_FAILED",
}
def print_text(result):
data_hash = hashlib.sha256(canonical_bytes(result)).hexdigest()
print("Bitflash UTXO proof verifier")
print("schema: %s" % result["schema"])
print("canonical verification sha256: %s" % data_hash)
print()
print("Target")
print(" outpoint: %s" % result["target"]["outpoint"])
print(" value: %s BTF" % result["target"]["value_btf"])
print(" height: %s" % result["target"]["created_height"])
print()
print("Commitment")
print(" expected: %s" % result["commitment"]["expected_root"])
print(" computed: %s" % result["commitment"]["computed_root"])
print(" path: %d sibling hashes" % result["commitment"]["path_length"])
print()
print("Checks")
for key in sorted(result["checks"]):
print(" %s %s" % ("OK " if result["checks"][key] else "FAIL", key))
if result["failures"]:
print()
print("Failures")
for failure in result["failures"]:
print(" - %s" % failure)
print()
print("Verdict: %s" % result["verdict"])
def main(argv):
ap = argparse.ArgumentParser(description=__doc__)
ap.add_argument("proof", help="canonical JSON proof from prove-utxo.py")
ap.add_argument("--root", help="expected UTXO root; defaults to root embedded in proof")
ap.add_argument("--json", action="store_true", help="print canonical JSON")
args = ap.parse_args(argv)
result = verify(load_proof(args.proof), args.root)
data = canonical_bytes(result)
if args.json:
sys.stdout.buffer.write(data)
else:
print_text(result)
return 0 if result["verdict"] == "UTXO_PROOF_VERIFIED" else 1
if __name__ == "__main__":
raise SystemExit(main(sys.argv[1:]))
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