Add reference.py with test vectors

* reference.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 <1466284+S3RK@users.noreply.github.com>
Co-Authored-By: Oghenovo Usiwoma <37949128+Eunovo@users.noreply.github.com>
Co-authored-by: S.Blagogee <34041358+setavenger@users.noreply.github.com>

bip-0352/bitcoin_utils.py

@@ -0,0 +1,158 @@
+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)