Merge pull request #33 from callebtc/fix/hash_to_curve

Fix/hash to curve

cashu/core/b_dhke.py

@@ -6,7 +6,7 @@ Alice:
 A = a*G
 return A
 Bob:
-Y = hash_to_point(secret_message)
+Y = hash_to_curve(secret_message)
 r = random blinding factor
 B'= Y + r*G
 return B'
@@ -20,7 +20,7 @@ C = C' - r*A
  (= a*Y)
 return C, secret_message
 Alice:
-Y = hash_to_point(secret_message)
+Y = hash_to_curve(secret_message)
 C == a*Y
 If true, C must have originated from Alice
 """
@@ -30,28 +30,22 @@ import hashlib
 from secp256k1 import PrivateKey, PublicKey
 
 
-def hash_to_point(secret_msg):
-    """Generates x coordinate from the message hash and checks if the point lies on the curve.
-    If it does not, it tries computing again a new x coordinate from the hash of the coordinate."""
+def hash_to_curve(message: bytes):
+    """Generates a point from the message hash and checks if the point lies on the curve.
+    If it does not, it tries computing a new point from the hash."""
     point = None
-    msg = secret_msg
+    msg_to_hash = message
     while point is None:
-        _hash = hashlib.sha256(msg).hexdigest().encode("utf-8")
         try:
-            # We construct compressed pub which has x coordinate encoded with even y
-            _hash = list(_hash[:33])  # take the 33 bytes and get a list of bytes
-            _hash[0] = 0x02  # set first byte to represent even y coord
-            _hash = bytes(_hash)
-            point = PublicKey(_hash, raw=True)
+            _hash = hashlib.sha256(msg_to_hash).digest()
+            point = PublicKey(b"\x02" + _hash, raw=True)
         except:
-            msg = _hash
-
+            msg_to_hash = _hash
     return point
 
 
-def step1_alice(secret_msg):
-    secret_msg = secret_msg.encode("utf-8")
-    Y = hash_to_point(secret_msg)
+def step1_alice(secret_msg: str):
+    Y = hash_to_curve(secret_msg.encode("utf-8"))
     r = PrivateKey()
     B_ = Y + r.pubkey
     return B_, r
@@ -68,7 +62,7 @@ def step3_alice(C_, r, A):
 
 
 def verify(a, C, secret_msg):
-    Y = hash_to_point(secret_msg.encode("utf-8"))
+    Y = hash_to_curve(secret_msg.encode("utf-8"))
     return C == Y.mult(a)
 
 

cashu/core/base.py

@@ -247,7 +247,7 @@ class MintKeyset:
         first_seen=None,
         active=None,
         seed: Union[None, str] = None,
-        derivation_path: str = "0",
+        derivation_path: str = None,
     ):
         self.derivation_path = derivation_path
         self.id = id

cashu/core/legacy.py

@@ -0,0 +1,27 @@
+import hashlib
+
+from secp256k1 import PublicKey
+
+
+def hash_to_point_pre_0_3_3(secret_msg):
+    """Generates x coordinate from the message hash and checks if the point lies on the curve.
+    If it does not, it tries computing again a new x coordinate from the hash of the coordinate."""
+    point = None
+    msg = secret_msg
+    while point is None:
+        _hash = hashlib.sha256(msg).hexdigest().encode("utf-8")
+        try:
+            # We construct compressed pub which has x coordinate encoded with even y
+            _hash = list(_hash[:33])  # take the 33 bytes and get a list of bytes
+            _hash[0] = 0x02  # set first byte to represent even y coord
+            _hash = bytes(_hash)
+            point = PublicKey(_hash, raw=True)
+        except:
+            msg = _hash
+
+    return point
+
+
+def verify_pre_0_3_3(a, C, secret_msg):
+    Y = hash_to_point_pre_0_3_3(secret_msg.encode("utf-8"))
+    return C == Y.mult(a)

cashu/core/settings.py

@@ -48,4 +48,4 @@ LNBITS_ENDPOINT = env.str("LNBITS_ENDPOINT", default=None)
 LNBITS_KEY = env.str("LNBITS_KEY", default=None)
 
 MAX_ORDER = 64
-VERSION = "0.3.2"
+VERSION = "0.3.3"

cashu/mint/__init__.py

@@ -1,4 +1,4 @@
 from cashu.core.settings import MINT_PRIVATE_KEY
 from cashu.mint.ledger import Ledger
 
-ledger = Ledger(MINT_PRIVATE_KEY, "data/mint")
+ledger = Ledger(MINT_PRIVATE_KEY, "data/mint", derivation_path="0/0/0/0")

cashu/mint/app.py

@@ -1,19 +1,30 @@
-import asyncio
 import logging
 import sys
 
 from fastapi import FastAPI
 from loguru import logger
+from starlette.middleware import Middleware
+from starlette.middleware.base import BaseHTTPMiddleware
+from starlette_context import context
+from starlette_context.middleware import RawContextMiddleware
 
 from cashu.core.settings import DEBUG, VERSION
-from cashu.lightning import WALLET
-from cashu.mint.migrations import m001_initial
 
-from . import ledger
 from .router import router
 from .startup import load_ledger
 
 
+class CustomHeaderMiddleware(BaseHTTPMiddleware):
+    """
+    Middleware for starlette that can set the context from request headers
+    """
+
+    async def dispatch(self, request, call_next):
+        context["client-version"] = request.headers.get("Client-version")
+        response = await call_next(request)
+        return response
+
+
 def create_app(config_object="core.settings") -> FastAPI:
     def configure_logger() -> None:
         class Formatter:
@@ -49,6 +60,13 @@ def create_app(config_object="core.settings") -> FastAPI:
 
     configure_logger()
 
+    middleware = [
+        Middleware(
+            RawContextMiddleware,
+        ),
+        Middleware(CustomHeaderMiddleware),
+    ]
+
     app = FastAPI(
         title="Cashu Mint",
         description="Ecash wallet and mint with Bitcoin Lightning support.",
@@ -57,8 +75,8 @@ def create_app(config_object="core.settings") -> FastAPI:
             "name": "MIT License",
             "url": "https://raw.githubusercontent.com/callebtc/cashu/main/LICENSE",
         },
+        middleware=middleware,
     )
-
     return app
 
 

cashu/mint/ledger.py

@@ -6,9 +6,11 @@ import math
 from typing import Dict, List, Set
 
 from loguru import logger
+from starlette_context import context
 
 import cashu.core.b_dhke as b_dhke
 import cashu.core.bolt11 as bolt11
+import cashu.core.legacy as legacy
 from cashu.core.base import (
     BlindedMessage,
     BlindedSignature,
@@ -55,11 +57,12 @@ class Ledger:
             seed=self.master_key, derivation_path=self.derivation_path
         )
         # check if current keyset is stored in db and store if not
+        logger.debug(f"Loading keyset {self.keyset.id} from db.")
         current_keyset_local: List[MintKeyset] = await get_keyset(
             id=self.keyset.id, db=self.db
         )
         if not len(current_keyset_local):
-            logger.debug(f"Storing keyset {self.keyset.id}")
+            logger.debug(f"Storing keyset {self.keyset.id}.")
             await store_keyset(keyset=self.keyset, db=self.db)
 
         # load all past keysets from db
@@ -112,6 +115,11 @@ class Ledger:
             secret_key = self.keysets.keysets[proof.id].private_keys[proof.amount]
 
         C = PublicKey(bytes.fromhex(proof.C), raw=True)
+
+        # backwards compatibility with old hash_to_curve
+        # old clients do not send a version
+        if not context.get("client-version"):
+            return legacy.verify_pre_0_3_3(secret_key, C, proof.secret)
         return b_dhke.verify(secret_key, C, proof.secret)
 
     def _verify_script(self, idx: int, proof: Proof):

cashu/mint/router.py

@@ -20,6 +20,10 @@ from cashu.mint import ledger
 router: APIRouter = APIRouter()
 
 
+from starlette.requests import Request
+from starlette_context import context
+
+
 @router.get("/keys")
 def keys():
     """Get the public keys of the mint"""
@@ -49,7 +53,6 @@ async def request_mint(amount: int = 0):
 @router.post("/mint")
 async def mint(
     payloads: MintRequest,
-    bolt11: Union[str, None] = None,
     payment_hash: Union[str, None] = None,
 ):
     """
@@ -70,7 +73,7 @@ async def mint(
 
 
 @router.post("/melt")
-async def melt(payload: MeltRequest):
+async def melt(request: Request, payload: MeltRequest):
     """
     Requests tokens to be destroyed and sent out via Lightning.
     """
@@ -97,7 +100,7 @@ async def check_fees(payload: CheckFeesRequest):
 
 
 @router.post("/split")
-async def split(payload: SplitRequest):
+async def split(request: Request, payload: SplitRequest):
     """
     Requetst a set of tokens with amount "total" to be split into two
     newly minted sets with amount "split" and "total-split".

cashu/wallet/wallet.py

@@ -30,7 +30,7 @@ from cashu.core.script import (
     step2_carol_sign_tx,
 )
 from cashu.core.secp import PublicKey
-from cashu.core.settings import DEBUG
+from cashu.core.settings import DEBUG, VERSION
 from cashu.core.split import amount_split
 from cashu.wallet.crud import (
     get_keyset,
@@ -52,7 +52,10 @@ class LedgerAPI:
         self.url = url
 
     async def _get_keys(self, url):
-        resp = requests.get(url + "/keys").json()
+        resp = requests.get(
+            url + "/keys",
+            headers={"Client-version": VERSION},
+        ).json()
         keys = resp
         assert len(keys), Exception("did not receive any keys")
         keyset_keys = {
@@ -63,7 +66,10 @@ class LedgerAPI:
         return keyset
 
     async def _get_keysets(self, url):
-        keysets = requests.get(url + "/keysets").json()
+        keysets = requests.get(
+            url + "/keysets",
+            headers={"Client-version": VERSION},
+        ).json()
         assert len(keysets), Exception("did not receive any keysets")
         return keysets
 
@@ -177,6 +183,7 @@ class LedgerAPI:
             self.url + "/mint",
             json=payloads.dict(),
             params={"payment_hash": payment_hash},
+            headers={"Client-version": VERSION},
         )
         resp.raise_for_status()
         try:
@@ -235,6 +242,7 @@ class LedgerAPI:
         resp = requests.post(
             self.url + "/split",
             json=split_payload.dict(include=_splitrequest_include_fields(proofs)),
+            headers={"Client-version": VERSION},
         )
         resp.raise_for_status()
         try:
@@ -260,6 +268,7 @@ class LedgerAPI:
         resp = requests.post(
             self.url + "/check",
             json=payload.dict(),
+            headers={"Client-version": VERSION},
         )
         resp.raise_for_status()
         return_dict = resp.json()
@@ -272,6 +281,7 @@ class LedgerAPI:
         resp = requests.post(
             self.url + "/checkfees",
             json=payload.dict(),
+            headers={"Client-version": VERSION},
         )
         resp.raise_for_status()
 
@@ -293,6 +303,7 @@ class LedgerAPI:
         resp = requests.post(
             self.url + "/melt",
             json=payload.dict(include=_meltequest_include_fields(proofs)),
+            headers={"Client-version": VERSION},
         )
         resp.raise_for_status()
 

docs/README.md

@@ -17,9 +17,9 @@ Mint: `Bob`
 
 # Blind Diffie-Hellmann key exchange (BDH)
 -   Mint `Bob` publishes `K = kG` 
--   `Alice` picks secret `x` and computes `Y = hash_to_point(x)` 
+-   `Alice` picks secret `x` and computes `Y = hash_to_curve(x)` 
 -   `Alice` sends to `Bob`: `T = Y + rG` with `r` being a random nonce
 -   `Bob` sends back to `Alice` blinded key: `Q = kT` (these two steps are the DH key exchange)
 -   `Alice` can calculate the unblinded key as `Q - rK = kY + krG - krG = kY = Z`
 -   Alice can take the pair `(x, Z)` as a token and can send it to `Carol`.
--   `Carol` can send `(x, Z)` to `Bob` who then checks that `k*hash_to_point(x) == Z`, and if so treats it as a valid spend of a token, adding `x`  to the list of spent secrets.
+-   `Carol` can send `(x, Z)` to `Bob` who then checks that `k*hash_to_curve(x) == Z`, and if so treats it as a valid spend of a token, adding `x`  to the list of spent secrets.

docs/specs/cashu_client_spec.md

@@ -17,12 +17,12 @@ Mint: `Bob`
 
 # Blind Diffie-Hellmann key exchange (BDH)
 -   Mint `Bob` publishes `K = kG` 
--   `Alice` picks secret `x` and computes `Y = hash_to_point(x)` 
+-   `Alice` picks secret `x` and computes `Y = hash_to_curve(x)` 
 -   `Alice` sends to `Bob`: `T = Y + rG` with `r` being a random nonce
 -   `Bob` sends back to `Alice` blinded key: `Q = kT` (these two steps are the DH key exchange)
 -   `Alice` can calculate the unblinded key as `Q - rK = kY + krG - krG = kY = Z`
 -   Alice can take the pair `(x, Z)` as a token and can send it to `Carol`.
--   `Carol` can send `(x, Z)` to `Bob` who then checks that `k*hash_to_point(x) == Z`, and if so treats it as a valid spend of a token, adding `x`  to the list of spent secrets.
+-   `Carol` can send `(x, Z)` to `Bob` who then checks that `k*hash_to_curve(x) == Z`, and if so treats it as a valid spend of a token, adding `x`  to the list of spent secrets.
 
 # Cashu client protocol
 

poetry.lock

@@ -167,8 +167,8 @@ starlette = "0.19.1"
 [package.extras]
 all = ["email_validator (>=1.1.1,<2.0.0)", "itsdangerous (>=1.1.0,<3.0.0)", "jinja2 (>=2.11.2,<4.0.0)", "orjson (>=3.2.1,<4.0.0)", "python-multipart (>=0.0.5,<0.0.6)", "pyyaml (>=5.3.1,<7.0.0)", "requests (>=2.24.0,<3.0.0)", "ujson (>=4.0.1,!=4.0.2,!=4.1.0,!=4.2.0,!=4.3.0,!=5.0.0,!=5.1.0,<6.0.0)", "uvicorn[standard] (>=0.12.0,<0.18.0)"]
 dev = ["autoflake (>=1.4.0,<2.0.0)", "flake8 (>=3.8.3,<6.0.0)", "passlib[bcrypt] (>=1.7.2,<2.0.0)", "pre-commit (>=2.17.0,<3.0.0)", "python-jose[cryptography] (>=3.3.0,<4.0.0)", "uvicorn[standard] (>=0.12.0,<0.18.0)"]
-doc = ["mdx-include (>=1.4.1,<2.0.0)", "mkdocs (>=1.1.2,<2.0.0)", "mkdocs-markdownextradata-plugin (>=0.1.7,<0.3.2)", "mkdocs-material (>=8.1.4,<9.0.0)", "pyyaml (>=5.3.1,<7.0.0)", "typer (>=0.4.1,<0.5.0)"]
-test = ["anyio[trio] (>=3.2.1,<4.0.0)", "black (==22.3.0)", "databases[sqlite] (>=0.3.2,<0.6.0)", "email_validator (>=1.1.1,<2.0.0)", "flake8 (>=3.8.3,<6.0.0)", "flask (>=1.1.2,<3.0.0)", "httpx (>=0.14.0,<0.19.0)", "isort (>=5.0.6,<6.0.0)", "mypy (==0.910)", "orjson (>=3.2.1,<4.0.0)", "peewee (>=3.13.3,<4.0.0)", "pytest (>=6.2.4,<7.0.0)", "pytest-cov (>=2.12.0,<4.0.0)", "python-multipart (>=0.0.5,<0.0.6)", "requests (>=2.24.0,<3.0.0)", "sqlalchemy (>=1.3.18,<1.5.0)", "types-dataclasses (==0.6.5)", "types-orjson (==3.6.2)", "types-ujson (==4.2.1)", "ujson (>=4.0.1,!=4.0.2,!=4.1.0,!=4.2.0,!=4.3.0,!=5.0.0,!=5.1.0,<6.0.0)"]
+doc = ["mdx-include (>=1.4.1,<2.0.0)", "mkdocs (>=1.1.2,<2.0.0)", "mkdocs-markdownextradata-plugin (>=0.1.7,<0.3.0)", "mkdocs-material (>=8.1.4,<9.0.0)", "pyyaml (>=5.3.1,<7.0.0)", "typer (>=0.4.1,<0.5.0)"]
+test = ["anyio[trio] (>=3.2.1,<4.0.0)", "black (==22.3.0)", "databases[sqlite] (>=0.3.3,<0.6.0)", "email_validator (>=1.1.1,<2.0.0)", "flake8 (>=3.8.3,<6.0.0)", "flask (>=1.1.2,<3.0.0)", "httpx (>=0.14.0,<0.19.0)", "isort (>=5.0.6,<6.0.0)", "mypy (==0.910)", "orjson (>=3.2.1,<4.0.0)", "peewee (>=3.13.3,<4.0.0)", "pytest (>=6.2.4,<7.0.0)", "pytest-cov (>=2.12.0,<4.0.0)", "python-multipart (>=0.0.5,<0.0.6)", "requests (>=2.24.0,<3.0.0)", "sqlalchemy (>=1.3.18,<1.5.0)", "types-dataclasses (==0.6.5)", "types-orjson (==3.6.2)", "types-ujson (==4.2.1)", "ujson (>=4.0.1,!=4.0.2,!=4.1.0,!=4.2.0,!=4.3.0,!=5.0.0,!=5.1.0,<6.0.0)"]
 
 [[package]]
 name = "h11"
@@ -553,6 +553,17 @@ typing-extensions = {version = ">=3.10.0", markers = "python_version < \"3.10\""
 [package.extras]
 full = ["itsdangerous", "jinja2", "python-multipart", "pyyaml", "requests"]
 
+[[package]]
+name = "starlette-context"
+version = "0.3.4"
+description = "Access context in Starlette"
+category = "main"
+optional = false
+python-versions = ">=3.7"
+
+[package.dependencies]
+starlette = "*"
+
 [[package]]
 name = "tomli"
 version = "2.0.1"
@@ -632,7 +643,7 @@ testing = ["func-timeout", "jaraco.itertools", "pytest (>=6)", "pytest-black (>=
 [metadata]
 lock-version = "1.1"
 python-versions = "^3.7"
-content-hash = "b4e980ee90226bab07750b1becc8c69df7752f6d168d200a79c782aa1efe61da"
+content-hash = "14ff9c57ca971c645f1a075b5c6fa0a84a38eaf6399d14afa724136728a3da03"
 
 [metadata.files]
 anyio = [
@@ -999,6 +1010,10 @@ starlette = [
     {file = "starlette-0.19.1-py3-none-any.whl", hash = "sha256:5a60c5c2d051f3a8eb546136aa0c9399773a689595e099e0877704d5888279bf"},
     {file = "starlette-0.19.1.tar.gz", hash = "sha256:c6d21096774ecb9639acad41b86b7706e52ba3bf1dc13ea4ed9ad593d47e24c7"},
 ]
+starlette-context = [
+    {file = "starlette_context-0.3.4-py37-none-any.whl", hash = "sha256:b16bf17bd3ead7ded2f458aebf7f913744b9cf28305e16c69b435a6c6ddf1135"},
+    {file = "starlette_context-0.3.4.tar.gz", hash = "sha256:2d28e1838302fb5d5adacadc10fb73fb2d5cca1f0aa1e279698701cc96f1567c"},
+]
 tomli = [
     {file = "tomli-2.0.1-py3-none-any.whl", hash = "sha256:939de3e7a6161af0c887ef91b7d41a53e7c5a1ca976325f429cb46ea9bc30ecc"},
     {file = "tomli-2.0.1.tar.gz", hash = "sha256:de526c12914f0c550d15924c62d72abc48d6fe7364aa87328337a31007fe8a4f"},

pyproject.toml

@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "cashu"
-version = "0.3.2"
+version = "0.3.3"
 description = "Ecash wallet and mint."
 authors = ["calle <callebtc@protonmail.com>"]
 license = "MIT"
@@ -22,6 +22,7 @@ bitstring = "^3.1.9"
 secp256k1 = "^0.14.0"
 sqlalchemy-aio = "^0.17.0"
 python-bitcoinlib = "^0.11.2"
+starlette-context = "^0.3.4"
 
 [tool.poetry.dev-dependencies]
 black = {version = "^22.8.0", allow-prereleases = true}

setup.py

@@ -13,7 +13,7 @@ entry_points = {"console_scripts": ["cashu = cashu.wallet.cli:cli"]}
 
 setuptools.setup(
     name="cashu",
-    version="0.3.2",
+    version="0.3.3",
     description="Ecash wallet and mint with Bitcoin Lightning support",
     long_description=long_description,
     long_description_content_type="text/markdown",