Add reference.py with test vectors

* refernece.py contains the silent payment specific code
* secp256k1.py for doing the EC operations
* bech32m.py contains code for encoding/decoding bech32(m) addresses
* bitcoin_utils.py contains some helper code, not specific to silent
  payments
* send_and_receive_test_vectors.json contains the wallet unit test
  vectors

Co-Authored-By: S3RK <[email protected]>
Co-Authored-By: Oghenovo Usiwoma <[email protected]>

bip-0352.mediawiki

@@ -370,6 +370,56 @@ If using a seed/seed phrase only style backup, the user can recover the wallet's
 
 Silent payments introduces a new address format and protocol for sending and as such is not compatible with older wallet software or wallets which have not implemented the silent payments protocol.
 
+== Test Vectors ==
+
+A [[bip-0352/send_and_receive_test_vectors.json|collection of test vectors in JSON format]] are provided, along with a [[bip-0352/reference.py|python reference implementation]]. Each test vector consists of a sending test case and corresponding receiving test case. This is to allow sending and receiving to be implemented separately. To ensure determinism while testing, sort the array of ''B<sub>m</sub>'' by amount (see the [[bip-0352/reference.py|reference implementation]]). Test cases use the following schema:
+
+''' test_case '''
+
+    {
+        "comment": "Comment describing the behavior being tested",
+        "sending": [<array of sender test objects>],
+        "receiving": [<array of recipient test objects>],
+    }
+
+''' sender '''
+
+    {
+        "given": {
+            "vin": [<array of vin objects with an added field for the private key. These objects are structured to match the `vin` output field from `getrawtransaction verbosity=2`>],
+            "recipients": [<array of strings, where each string is a bech32m encoding representing a silent payment address>]
+        },
+        "expected": {
+            "outputs": [<array of strings, where each string is a hex encoding of 32-byte X-only public key>]
+        },
+    }
+
+''' recipient '''
+
+    {
+        "given": {
+            "vin": [<array of vin objects. These objects are structured to match the `vin` output field from `getrawtransaction verbosity=2`>],
+            "key_material": {
+                "scan_priv_key": <hex encoded scan private key>,
+                "spend_priv_key": <hex encoded spend private key>,
+            }
+            "labels": [<array of ints, representing labels the receiver has used>],
+         },
+         "expected": {
+             "addresses": [<array of bech32m strings, one for the silent payment address and each labeled address (if used)>],
+             "outputs": [
+                 {
+                     "pub_key": <hex encoded X-only public key>,
+                     "priv_key_tweak": <hex encoded private key tweak data>.
+                     "signature": <hex encoded signature for the output (produced with spend_priv_key + priv_key_tweak)>
+                 },
+                 ...
+             ]
+         }
+     }
+
+Wallets should include inputs not in the ''[[#inputs-for-shared-secret-derivation|Inputs For Shared Secret Derivation]]'' list when testing to ensure that only inputs from the list are being used for shared secret derivation. Additionally, receiving wallets should include non-silent payment outputs for themselves in testing to ensure silent payments scanning does not interfere with regular outputs detection.
+
 === Functional tests ===
 
 Below is a list of functional tests which should be included in sending and receiving implementations.

bip-0352/bech32m.py

@@ -0,0 +1,135 @@
+# Copyright (c) 2017, 2020 Pieter Wuille
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+
+"""Reference implementation for Bech32/Bech32m and segwit addresses."""
+
+
+from enum import Enum
+
+class Encoding(Enum):
+    """Enumeration type to list the various supported encodings."""
+    BECH32 = 1
+    BECH32M = 2
+
+CHARSET = "qpzry9x8gf2tvdw0s3jn54khce6mua7l"
+BECH32M_CONST = 0x2bc830a3
+
+def bech32_polymod(values):
+    """Internal function that computes the Bech32 checksum."""
+    generator = [0x3b6a57b2, 0x26508e6d, 0x1ea119fa, 0x3d4233dd, 0x2a1462b3]
+    chk = 1
+    for value in values:
+        top = chk >> 25
+        chk = (chk & 0x1ffffff) << 5 ^ value
+        for i in range(5):
+            chk ^= generator[i] if ((top >> i) & 1) else 0
+    return chk
+
+
+def bech32_hrp_expand(hrp):
+    """Expand the HRP into values for checksum computation."""
+    return [ord(x) >> 5 for x in hrp] + [0] + [ord(x) & 31 for x in hrp]
+
+
+def bech32_verify_checksum(hrp, data):
+    """Verify a checksum given HRP and converted data characters."""
+    const = bech32_polymod(bech32_hrp_expand(hrp) + data)
+    if const == 1:
+        return Encoding.BECH32
+    if const == BECH32M_CONST:
+        return Encoding.BECH32M
+    return None
+
+def bech32_create_checksum(hrp, data, spec):
+    """Compute the checksum values given HRP and data."""
+    values = bech32_hrp_expand(hrp) + data
+    const = BECH32M_CONST if spec == Encoding.BECH32M else 1
+    polymod = bech32_polymod(values + [0, 0, 0, 0, 0, 0]) ^ const
+    return [(polymod >> 5 * (5 - i)) & 31 for i in range(6)]
+
+
+def bech32_encode(hrp, data, spec):
+    """Compute a Bech32 string given HRP and data values."""
+    combined = data + bech32_create_checksum(hrp, data, spec)
+    return hrp + '1' + ''.join([CHARSET[d] for d in combined])
+
+def bech32_decode(bech):
+    """Validate a Bech32/Bech32m string, and determine HRP and data."""
+    if ((any(ord(x) < 33 or ord(x) > 126 for x in bech)) or
+            (bech.lower() != bech and bech.upper() != bech)):
+        return (None, None, None)
+    bech = bech.lower()
+    pos = bech.rfind('1')
+
+    # remove the requirement that bech32m be less than 90 chars
+    if pos < 1 or pos + 7 > len(bech):
+        return (None, None, None)
+    if not all(x in CHARSET for x in bech[pos+1:]):
+        return (None, None, None)
+    hrp = bech[:pos]
+    data = [CHARSET.find(x) for x in bech[pos+1:]]
+    spec = bech32_verify_checksum(hrp, data)
+    if spec is None:
+        return (None, None, None)
+    return (hrp, data[:-6], spec)
+
+def convertbits(data, frombits, tobits, pad=True):
+    """General power-of-2 base conversion."""
+    acc = 0
+    bits = 0
+    ret = []
+    maxv = (1 << tobits) - 1
+    max_acc = (1 << (frombits + tobits - 1)) - 1
+    for value in data:
+        if value < 0 or (value >> frombits):
+            return None
+        acc = ((acc << frombits) | value) & max_acc
+        bits += frombits
+        while bits >= tobits:
+            bits -= tobits
+            ret.append((acc >> bits) & maxv)
+    if pad:
+        if bits:
+            ret.append((acc << (tobits - bits)) & maxv)
+    elif bits >= frombits or ((acc << (tobits - bits)) & maxv):
+        return None
+    return ret
+
+
+def decode(hrp, addr):
+    """Decode a segwit address."""
+    hrpgot, data, spec = bech32_decode(addr)
+    if hrpgot != hrp:
+        return (None, None)
+    decoded = convertbits(data[1:], 5, 8, False)
+    if decoded is None or len(decoded) < 2:
+        return (None, None)
+    if data[0] > 16:
+        return (None, None)
+    return (data[0], decoded)
+
+
+def encode(hrp, witver, witprog):
+    """Encode a segwit address."""
+    spec = Encoding.BECH32 if witver == 0 else Encoding.BECH32M
+    ret = bech32_encode(hrp, [witver] + convertbits(witprog, 8, 5), spec)
+    if decode(hrp, ret) == (None, None):
+        return None
+    return ret

bip-0352/bitcoin_utils.py

@@ -0,0 +1,162 @@
+import hashlib
+import struct
+from io import BytesIO
+from secp256k1 import ECKey
+from typing import Union
+
+
+def from_hex(hex_string):
+    """Deserialize from a hex string representation (e.g. from RPC)"""
+    return BytesIO(bytes.fromhex(hex_string))
+
+
+def ser_uint32(u: int) -> bytes:
+    return u.to_bytes(4, "big")
+
+
+def ser_uint256(u):
+    return u.to_bytes(32, 'little')
+
+
+def deser_uint256(f):
+    return int.from_bytes(f.read(32), 'little')
+
+
+def deser_txid(txid: str):
+    # recall that txids are serialized little-endian, but displayed big-endian
+    # this means when converting from a human readable hex txid, we need to first
+    # reverse it before deserializing it
+    dixt = "".join(map(str.__add__, txid[-2::-2], txid[-1::-2]))
+    return bytes.fromhex(dixt)
+
+
+def deser_compact_size(f: BytesIO):
+    view = f.getbuffer()
+    nbytes = view.nbytes;
+    view.release()
+    if (nbytes == 0):
+        return 0 # end of stream
+
+    nit = struct.unpack("<B", f.read(1))[0]
+    if nit == 253:
+        nit = struct.unpack("<H", f.read(2))[0]
+    elif nit == 254:
+        nit = struct.unpack("<I", f.read(4))[0]
+    elif nit == 255:
+        nit = struct.unpack("<Q", f.read(8))[0]
+    return nit
+
+
+def deser_string(f: BytesIO):
+    nit = deser_compact_size(f)
+    return f.read(nit)
+
+
+def deser_string_vector(f: BytesIO):
+    nit = deser_compact_size(f)
+    r = []
+    for _ in range(nit):
+        t = deser_string(f)
+        r.append(t)
+    return r
+
+
+class COutPoint:
+    __slots__ = ("hash", "n",)
+
+    def __init__(self, hash=b"", n=0,):
+        self.hash = hash
+        self.n = n
+
+    def serialize(self):
+        r = b""
+        r += self.hash
+        r += struct.pack("<I", self.n)
+        return r
+
+    def deserialize(self, f):
+        self.hash = f.read(32)
+        self.n = struct.unpack("<I", f.read(4))[0]
+
+
+class VinInfo:
+    __slots__ = ("outpoint", "scriptSig", "txinwitness", "prevout", "private_key")
+
+    def __init__(self, outpoint=None, scriptSig=b"", txinwitness=None, prevout=b"", private_key=None):
+        if outpoint is None:
+            self.outpoint = COutPoint()
+        else:
+            self.outpoint = outpoint
+        if txinwitness is None:
+            self.txinwitness = CTxInWitness()
+        else:
+            self.txinwitness = txinwitness
+        if private_key is None:
+            self.private_key = ECKey()
+        else:
+            self.private_key = private_key
+        self.scriptSig = scriptSig
+        self.prevout = prevout
+
+
+class CScriptWitness:
+    __slots__ = ("stack",)
+
+    def __init__(self):
+        # stack is a vector of strings
+        self.stack = []
+
+    def is_null(self):
+        if self.stack:
+            return False
+        return True
+
+
+class CTxInWitness:
+    __slots__ = ("scriptWitness",)
+
+    def __init__(self):
+        self.scriptWitness = CScriptWitness()
+
+    def deserialize(self, f: BytesIO):
+        self.scriptWitness.stack = deser_string_vector(f)
+        return self
+
+    def is_null(self):
+        return self.scriptWitness.is_null()
+
+
+def hash160(s: Union[bytes, bytearray]) -> bytes:
+    return hashlib.new("ripemd160", hashlib.sha256(s).digest()).digest()
+
+
+def is_p2tr(spk: bytes) -> bool:
+    if len(spk) != 34:
+        return False
+    # OP_1 OP_PUSHBYTES_32 <32 bytes>
+    return (spk[0] == 0x51) & (spk[1] == 0x20)
+
+
+def is_p2wpkh(spk: bytes) -> bool:
+    if len(spk) != 22:
+        return False
+    # OP_0 OP_PUSHBYTES_20 <20 bytes>
+    return (spk[0] == 0x00) & (spk[1] == 0x14)
+
+
+def is_p2sh(spk: bytes) -> bool:
+    if len(spk) != 23:
+        return False
+    # OP_HASH160 OP_PUSHBYTES_20 <20 bytes> OP_EQUAL
+    return (spk[0] == 0xA9) & (spk[1] == 0x14) & (spk[-1] == 0x87)
+
+
+def is_p2pkh(spk: bytes) -> bool:
+    if len(spk) != 25:
+        return False
+    # OP_DUP OP_HASH160 OP_PUSHBYTES_20 <20 bytes> OP_EQUALVERIFY OP_CHECKSIG
+    return (spk[0] == 0x76) & (spk[1] == 0xA9) & (spk[2] == 0x14) & (spk[-2] == 0x88) & (spk[-1] == 0xAC)
+
+
+
+