Initial BIP-352 support

src/embit/bip352.py

@@ -0,0 +1,45 @@
+"""
+BIP-352: Silent Payments
+see: https://github.com/bitcoin/bips/blob/master/bip-0352.mediawiki
+
+TODO:
+* Implement deriving a destination addr for a given output and recipient SP address.
+* Implement check to determine if a given output is an SP output for a given SP address.
+* Implement signing SP spends (once psbt format is settled).
+"""
+from embit import bech32, ec
+from embit.util import secp256k1
+from embit.hashes import tagged_hash
+
+
+
+def generate_silent_payment_address(B_scan: ec.PublicKey, B_spend: ec.PublicKey, network: str = "main", version: int = 0) -> str:
+    """
+    Adapted from https://github.com/bitcoin/bips/blob/master/bip-0352/reference.py
+    """
+    data = bech32.convertbits(B_scan.sec() + B_spend.sec(), 8, 5)
+    hrp = "sp" if network == "main" else "tsp"
+    return bech32.bech32_encode(bech32.Encoding.BECH32M, hrp, [version] + data)
+
+
+
+def generate_labeled_silent_payment_address(b_scan: ec.PrivateKey, B_spend: ec.PublicKey, label, network: str = "main", version: int = 0) -> str:
+    """
+    The spending key is tweaked with the label to generate a labeled silent payment address.
+    see: https://github.com/bitcoin/bips/blob/master/bip-0352.mediawiki#address-encoding
+
+    `label` must be an int, str, or bytes.
+    """
+    if isinstance(label, int):
+        label_bytes = label.to_bytes(4, "big")
+    elif isinstance(label, str):
+        label_bytes = label.encode()
+    elif isinstance(label, bytes):
+        label_bytes = label
+    else:
+        raise Exception("Label must be an int, str, or bytes.")
+
+    tweak = tagged_hash("BIP0352/Label", b_scan.secret + label_bytes)
+    label_pubkey = ec.PublicKey(secp256k1.ec_pubkey_add(secp256k1.ec_pubkey_parse(B_spend.sec()), tweak))
+
+    return generate_silent_payment_address(b_scan.get_public_key(), label_pubkey, network=network, version=version)

tests/tests/test_bip352.py

@@ -0,0 +1,86 @@
+"""
+BIP-352 test vectors:
+https://github.com/bitcoin/bips/blob/master/bip-0352/send_and_receive_test_vectors.json
+"""
+
+from binascii import unhexlify
+from unittest import TestCase
+
+import pytest
+from embit import bip352
+from embit.ec import PrivateKey
+from embit.networks import NETWORKS
+
+
+BASIC_TEST_VECTORS = [
+    {
+        "spend_priv_key": "9d6ad855ce3417ef84e836892e5a56392bfba05fa5d97ccea30e266f540e08b3",
+        "scan_priv_key": "0f694e068028a717f8af6b9411f9a133dd3565258714cc226594b34db90c1f2c",
+        "sp_address": "sp1qqgste7k9hx0qftg6qmwlkqtwuy6cycyavzmzj85c6qdfhjdpdjtdgqjuexzk6murw56suy3e0rd2cgqvycxttddwsvgxe2usfpxumr70xc9pkqwv"
+    },
+    {
+        "spend_priv_key": "0000000000000000000000000000000000000000000000000000000000000001",
+        "scan_priv_key": "0000000000000000000000000000000000000000000000000000000000000002",
+        "sp_address": "sp1qqtrqglu5g8kh6mfsg4qxa9wq0nv9cauwfwxw70984wkqnw2uwz0w2qnehen8a7wuhwk9tgrzjh8gwzc8q2dlekedec5djk0js9d3d7qhnq6lqj3s"
+    }
+]
+
+
+LABEL_TEST_VECTORS = {
+    "spend_priv_key": "9d6ad855ce3417ef84e836892e5a56392bfba05fa5d97ccea30e266f540e08b3",
+    "scan_priv_key": "0f694e068028a717f8af6b9411f9a133dd3565258714cc226594b34db90c1f2c",
+    "labels": [
+        2,
+        3,
+        1001337
+    ],
+    "addresses": [
+        "sp1qqgste7k9hx0qftg6qmwlkqtwuy6cycyavzmzj85c6qdfhjdpdjtdgqjex54dmqmmv6rw353tsuqhs99ydvadxzrsy9nuvk74epvee55drs734pqq",
+        "sp1qqgste7k9hx0qftg6qmwlkqtwuy6cycyavzmzj85c6qdfhjdpdjtdgqsg59z2rppn4qlkx0yz9sdltmjv3j8zgcqadjn4ug98m3t6plujsq9qvu5n",
+        "sp1qqgste7k9hx0qftg6qmwlkqtwuy6cycyavzmzj85c6qdfhjdpdjtdgq7c2zfthc6x3a5yecwc52nxa0kfd20xuz08zyrjpfw4l2j257yq6qgnkdh5"
+    ]
+}
+
+
+class BIP352Test(TestCase):
+    def test_generate_silent_payment_address(self):
+        """ Should generate the expected silent payment address """
+        for test_vector in BASIC_TEST_VECTORS:
+            spend_priv_key = PrivateKey(unhexlify(test_vector["spend_priv_key"]))
+            scan_priv_key = PrivateKey(unhexlify(test_vector["scan_priv_key"]))
+            sp_address = bip352.generate_silent_payment_address(scan_priv_key.get_public_key(), spend_priv_key.get_public_key())
+            assert sp_address == test_vector["sp_address"]
+
+
+    def test_generate_silent_payment_address_for_network(self):
+        """ Test network silent payment addrs should start with "tsp" """
+        test_networks = [k for k in NETWORKS.keys() if k != "main"]
+        scan_pubkey = PrivateKey(unhexlify(BASIC_TEST_VECTORS[0]["spend_priv_key"])).get_public_key()
+        spend_pubkey = PrivateKey(unhexlify(BASIC_TEST_VECTORS[0]["scan_priv_key"])).get_public_key()
+
+        for network in test_networks:
+            payment_addr = bip352.generate_silent_payment_address(scan_pubkey, spend_pubkey, network=network)
+            assert payment_addr.startswith("tsp")
+
+
+    def test_generate_labeled_silent_payment_address(self):
+        """ Should generate the expected labeled silent payment addresses """
+        spend_priv_key = PrivateKey(unhexlify(LABEL_TEST_VECTORS["spend_priv_key"]))
+        scan_priv_key = PrivateKey(unhexlify(LABEL_TEST_VECTORS["scan_priv_key"]))
+        for label, address in zip(LABEL_TEST_VECTORS["labels"], LABEL_TEST_VECTORS["addresses"]):
+            sp_address = bip352.generate_labeled_silent_payment_address(scan_priv_key, spend_priv_key.get_public_key(), label)
+            assert sp_address == address
+
+        # Label may also be a string, but the bip does not provide any test vectors
+        bip352.generate_labeled_silent_payment_address(scan_priv_key, spend_priv_key.get_public_key(), label="tenant 6102")
+
+        # Label may also be passed in as bytes
+        bip352.generate_labeled_silent_payment_address(scan_priv_key, spend_priv_key.get_public_key(), label="I am bytes".encode())
+
+        with pytest.raises(Exception):
+            # Label is required
+            bip352.generate_labeled_silent_payment_address(scan_priv_key, spend_priv_key.get_public_key())
+
+        with pytest.raises(Exception):
+            # Label must be an int, str, or bytes
+            bip352.generate_labeled_silent_payment_address(scan_priv_key, spend_priv_key.get_public_key(), label=1.0)