Wallet: deprecate old hash to curve (#457)

* wallet: deprecate old hash to curve

* fix order

cashu/core/crypto/b_dhke.py

@@ -55,26 +55,10 @@ from typing import Optional, Tuple
 
 from secp256k1 import PrivateKey, PublicKey
 
-
-def hash_to_curve(message: bytes) -> PublicKey:
-    """Generates a point from the message hash and checks if the point lies on the curve.
-    If it does not, iteratively tries to compute a new point from the hash."""
-    point = None
-    msg_to_hash = message
-    while point is None:
-        _hash = hashlib.sha256(msg_to_hash).digest()
-        try:
-            # will error if point does not lie on curve
-            point = PublicKey(b"\x02" + _hash, raw=True)
-        except Exception:
-            msg_to_hash = _hash
-    return point
-
-
 DOMAIN_SEPARATOR = b"Secp256k1_HashToCurve_Cashu_"
 
 
-def hash_to_curve_domain_separated(message: bytes) -> PublicKey:
+def hash_to_curve(message: bytes) -> PublicKey:
     """Generates a secp256k1 point from a message.
 
     The point is generated by hashing the message with a domain separator and then
@@ -110,15 +94,6 @@ def step1_alice(
     return B_, r
 
 
-def step1_alice_domain_separated(
-    secret_msg: str, blinding_factor: Optional[PrivateKey] = None
-) -> tuple[PublicKey, PrivateKey]:
-    Y: PublicKey = hash_to_curve_domain_separated(secret_msg.encode("utf-8"))
-    r = blinding_factor or PrivateKey()
-    B_: PublicKey = Y + r.pubkey  # type: ignore
-    return B_, r
-
-
 def step2_bob(B_: PublicKey, a: PrivateKey) -> Tuple[PublicKey, PrivateKey, PrivateKey]:
     C_: PublicKey = B_.mult(a)  # type: ignore
     # produce dleq proof
@@ -136,17 +111,11 @@ def verify(a: PrivateKey, C: PublicKey, secret_msg: str) -> bool:
     valid = C == Y.mult(a)  # type: ignore
     # BEGIN: BACKWARDS COMPATIBILITY < 0.15.1
     if not valid:
-        valid = verify_domain_separated(a, C, secret_msg)
+        valid = verify_deprecated(a, C, secret_msg)
     # END: BACKWARDS COMPATIBILITY < 0.15.1
     return valid
 
 
-def verify_domain_separated(a: PrivateKey, C: PublicKey, secret_msg: str) -> bool:
-    Y: PublicKey = hash_to_curve_domain_separated(secret_msg.encode("utf-8"))
-    valid = C == Y.mult(a)  # type: ignore
-    return valid
-
-
 def hash_e(*publickeys: PublicKey) -> bytes:
     e_ = ""
     for p in publickeys:
@@ -202,12 +171,45 @@ def carol_verify_dleq(
     valid = alice_verify_dleq(B_, C_, e, s, A)
     # BEGIN: BACKWARDS COMPATIBILITY < 0.15.1
     if not valid:
-        return carol_verify_dleq_domain_separated(secret_msg, r, C, e, s, A)
+        return carol_verify_dleq_deprecated(secret_msg, r, C, e, s, A)
     # END: BACKWARDS COMPATIBILITY < 0.15.1
     return valid
 
 
-def carol_verify_dleq_domain_separated(
+# -------- Deprecated hash_to_curve before 0.15.0 --------
+
+
+def hash_to_curve_deprecated(message: bytes) -> PublicKey:
+    """Generates a point from the message hash and checks if the point lies on the curve.
+    If it does not, iteratively tries to compute a new point from the hash."""
+    point = None
+    msg_to_hash = message
+    while point is None:
+        _hash = hashlib.sha256(msg_to_hash).digest()
+        try:
+            # will error if point does not lie on curve
+            point = PublicKey(b"\x02" + _hash, raw=True)
+        except Exception:
+            msg_to_hash = _hash
+    return point
+
+
+def step1_alice_deprecated(
+    secret_msg: str, blinding_factor: Optional[PrivateKey] = None
+) -> tuple[PublicKey, PrivateKey]:
+    Y: PublicKey = hash_to_curve_deprecated(secret_msg.encode("utf-8"))
+    r = blinding_factor or PrivateKey()
+    B_: PublicKey = Y + r.pubkey  # type: ignore
+    return B_, r
+
+
+def verify_deprecated(a: PrivateKey, C: PublicKey, secret_msg: str) -> bool:
+    Y: PublicKey = hash_to_curve_deprecated(secret_msg.encode("utf-8"))
+    valid = C == Y.mult(a)  # type: ignore
+    return valid
+
+
+def carol_verify_dleq_deprecated(
     secret_msg: str,
     r: PrivateKey,
     C: PublicKey,
@@ -215,7 +217,7 @@ def carol_verify_dleq_domain_separated(
     s: PrivateKey,
     A: PublicKey,
 ) -> bool:
-    Y: PublicKey = hash_to_curve_domain_separated(secret_msg.encode("utf-8"))
+    Y: PublicKey = hash_to_curve_deprecated(secret_msg.encode("utf-8"))
     C_: PublicKey = C + A.mult(r)  # type: ignore
     B_: PublicKey = Y + r.pubkey  # type: ignore
     valid = alice_verify_dleq(B_, C_, e, s, A)

cashu/core/settings.py

@@ -123,7 +123,7 @@ class WalletSettings(CashuSettings):
     mint_port: int = Field(default=3338)
     wallet_name: str = Field(default="wallet")
     wallet_unit: str = Field(default="sat")
-    wallet_domain_separation: bool = Field(default=False)
+    wallet_use_deprecated_h2c: bool = Field(default=False)
     api_port: int = Field(default=4448)
     api_host: str = Field(default="127.0.0.1")
 

cashu/wallet/wallet.py

@@ -998,9 +998,11 @@ class Wallet(LedgerAPI, WalletP2PK, WalletHTLC, WalletSecrets):
         # NUT-08, the mint will imprint these outputs with a value depending on the
         # amount of fees we overpaid.
         n_change_outputs = calculate_number_of_blank_outputs(fee_reserve_sat)
-        change_secrets, change_rs, change_derivation_paths = (
+        (
-            await self.generate_n_secrets(n_change_outputs)
+            change_secrets,
-        )
+            change_rs,
+            change_derivation_paths,
+        ) = await self.generate_n_secrets(n_change_outputs)
         change_outputs, change_rs = self._construct_outputs(
             n_change_outputs * [1], change_secrets, change_rs
         )
@@ -1126,14 +1128,15 @@ class Wallet(LedgerAPI, WalletP2PK, WalletHTLC, WalletSecrets):
             C = b_dhke.step3_alice(
                 C_, r, self.keysets[promise.id].public_keys[promise.amount]
             )
-            # BEGIN: BACKWARDS COMPATIBILITY < 0.15.1
+
-            if not settings.wallet_domain_separation:
+            if not settings.wallet_use_deprecated_h2c:
                 B_, r = b_dhke.step1_alice(secret, r)  # recompute B_ for dleq proofs
-            # END: BACKWARDS COMPATIBILITY < 0.15.1
+            # BEGIN: BACKWARDS COMPATIBILITY < 0.15.1
             else:
-                B_, r = b_dhke.step1_alice_domain_separated(
+                B_, r = b_dhke.step1_alice_deprecated(
                     secret, r
                 )  # recompute B_ for dleq proofs
+            # END: BACKWARDS COMPATIBILITY < 0.15.1
 
             proof = Proof(
                 id=promise.id,
@@ -1196,12 +1199,13 @@ class Wallet(LedgerAPI, WalletP2PK, WalletHTLC, WalletSecrets):
         rs_ = [None] * len(amounts) if not rs else rs
         rs_return: List[PrivateKey] = []
         for secret, amount, r in zip(secrets, amounts, rs_):
-            # BEGIN: BACKWARDS COMPATIBILITY < 0.15.1
+            if not settings.wallet_use_deprecated_h2c:
-            if not settings.wallet_domain_separation:
                 B_, r = b_dhke.step1_alice(secret, r or None)
-            # END: BACKWARDS COMPATIBILITY < 0.15.1
+            # BEGIN: BACKWARDS COMPATIBILITY < 0.15.1
             else:
-                B_, r = b_dhke.step1_alice_domain_separated(secret, r or None)
+                B_, r = b_dhke.step1_alice_deprecated(secret, r or None)
+            # END: BACKWARDS COMPATIBILITY < 0.15.1
+
             rs_return.append(r)
             output = BlindedMessage(
                 amount=amount, B_=B_.serialize().hex(), id=self.keyset_id

tests/test_crypto.py

@@ -1,12 +1,11 @@
 from cashu.core.crypto.b_dhke import (
     alice_verify_dleq,
     carol_verify_dleq,
-    carol_verify_dleq_domain_separated,
     hash_e,
     hash_to_curve,
-    hash_to_curve_domain_separated,
+    hash_to_curve_deprecated,
     step1_alice,
-    step1_alice_domain_separated,
+    step1_alice_deprecated,
     step2_bob,
     step2_bob_dleq,
     step3_alice,
@@ -22,9 +21,11 @@ def test_hash_to_curve():
     )
     assert (
         result.serialize().hex()
-        == "0266687aadf862bd776c8fc18b8e9f8e20089714856ee233b3902a591d0d5f2925"
+        == "024cce997d3b518f739663b757deaec95bcd9473c30a14ac2fd04023a739d1a725"
     )
 
+
+def test_hash_to_curve_iteration():
     result = hash_to_curve(
         bytes.fromhex(
             "0000000000000000000000000000000000000000000000000000000000000001"
@@ -32,20 +33,7 @@ def test_hash_to_curve():
     )
     assert (
         result.serialize().hex()
-        == "02ec4916dd28fc4c10d78e287ca5d9cc51ee1ae73cbfde08c6b37324cbfaac8bc5"
+        == "022e7158e11c9506f1aa4248bf531298daa7febd6194f003edcd9b93ade6253acf"
-    )
-
-
-def test_hash_to_curve_iteration():
-    """This input causes multiple rounds of the hash_to_curve algorithm."""
-    result = hash_to_curve(
-        bytes.fromhex(
-            "0000000000000000000000000000000000000000000000000000000000000002"
-        )
-    )
-    assert (
-        result.serialize().hex()
-        == "02076c988b353fcbb748178ecb286bc9d0b4acf474d4ba31ba62334e46c97c416a"
     )
 
 
@@ -62,7 +50,7 @@ def test_step1():
 
     assert (
         B_.serialize().hex()
-        == "02a9acc1e48c25eeeb9289b5031cc57da9fe72f3fe2861d264bdc074209b107ba2"
+        == "025cc16fe33b953e2ace39653efb3e7a7049711ae1d8a2f7a9108753f1cdea742b"
     )
     assert blinding_factor.private_key == bytes.fromhex(
         "0000000000000000000000000000000000000000000000000000000000000001"
@@ -88,7 +76,7 @@ def test_step2():
     C_, e, s = step2_bob(B_, a)
     assert (
         C_.serialize().hex()
-        == "02a9acc1e48c25eeeb9289b5031cc57da9fe72f3fe2861d264bdc074209b107ba2"
+        == "025cc16fe33b953e2ace39653efb3e7a7049711ae1d8a2f7a9108753f1cdea742b"
     )
 
 
@@ -97,7 +85,7 @@ def test_step3():
     # C_ from test_step2
     C_ = PublicKey(
         bytes.fromhex(
-            "02a9acc1e48c25eeeb9289b5031cc57da9fe72f3fe2861d264bdc074209b107ba2"
+            "025cc16fe33b953e2ace39653efb3e7a7049711ae1d8a2f7a9108753f1cdea742b"
         ),
         raw=True,
     )
@@ -118,7 +106,7 @@ def test_step3():
 
     assert (
         C.serialize().hex()
-        == "03c724d7e6a5443b39ac8acf11f40420adc4f99a02e7cc1b57703d9391f6d129cd"
+        == "0271bf0d702dbad86cbe0af3ab2bfba70a0338f22728e412d88a830ed0580b9de4"
     )
 
 
@@ -176,11 +164,11 @@ def test_dleq_step2_bob_dleq():
     e, s = step2_bob_dleq(B_, a, p_bytes)
     assert (
         e.serialize()
-        == "9818e061ee51d5c8edc3342369a554998ff7b4381c8652d724cdf46429be73d9"
+        == "a608ae30a54c6d878c706240ee35d4289b68cfe99454bbfa6578b503bce2dbe1"
     )
     assert (
         s.serialize()
-        == "9818e061ee51d5c8edc3342369a554998ff7b4381c8652d724cdf46429be73da"
+        == "a608ae30a54c6d878c706240ee35d4289b68cfe99454bbfa6578b503bce2dbe2"
     )  # differs from e only in least significant byte because `a = 0x1`
 
     # change `a`
@@ -193,11 +181,11 @@ def test_dleq_step2_bob_dleq():
     e, s = step2_bob_dleq(B_, a, p_bytes)
     assert (
         e.serialize()
-        == "df1984d5c22f7e17afe33b8669f02f530f286ae3b00a1978edaf900f4721f65e"
+        == "076cbdda4f368053c33056c438df014d1875eb3c8b28120bece74b6d0e6381bb"
     )
     assert (
         s.serialize()
-        == "828404170c86f240c50ae0f5fc17bb6b82612d46b355e046d7cd84b0a3c934a0"
+        == "b6d41ac1e12415862bf8cace95e5355e9262eab8a11d201dadd3b6e41584ea6e"
     )
 
 
@@ -306,36 +294,47 @@ def test_dleq_carol_verify_from_bob():
     assert carol_verify_dleq(secret_msg=secret_msg, C=C, r=r, e=e, s=s, A=A)
 
 
-# TESTS FOR DOMAIN SEPARATED HASH TO CURVE
+# TESTS FOR DEPRECATED HASH TO CURVE
 
 
-def test_hash_to_curve_domain_separated():
+def test_hash_to_curve_deprecated():
-    result = hash_to_curve_domain_separated(
+    result = hash_to_curve_deprecated(
         bytes.fromhex(
             "0000000000000000000000000000000000000000000000000000000000000000"
         )
     )
     assert (
         result.serialize().hex()
-        == "024cce997d3b518f739663b757deaec95bcd9473c30a14ac2fd04023a739d1a725"
+        == "0266687aadf862bd776c8fc18b8e9f8e20089714856ee233b3902a591d0d5f2925"
     )
 
-
+    result = hash_to_curve_deprecated(
-def test_hash_to_curve_domain_separated_iterative():
-    result = hash_to_curve_domain_separated(
         bytes.fromhex(
             "0000000000000000000000000000000000000000000000000000000000000001"
         )
     )
     assert (
         result.serialize().hex()
-        == "022e7158e11c9506f1aa4248bf531298daa7febd6194f003edcd9b93ade6253acf"
+        == "02ec4916dd28fc4c10d78e287ca5d9cc51ee1ae73cbfde08c6b37324cbfaac8bc5"
     )
 
 
-def test_step1_domain_separated():
+def test_hash_to_curve_iteration_deprecated():
+    """This input causes multiple rounds of the hash_to_curve algorithm."""
+    result = hash_to_curve_deprecated(
+        bytes.fromhex(
+            "0000000000000000000000000000000000000000000000000000000000000002"
+        )
+    )
+    assert (
+        result.serialize().hex()
+        == "02076c988b353fcbb748178ecb286bc9d0b4acf474d4ba31ba62334e46c97c416a"
+    )
+
+
+def test_step1_deprecated():
     secret_msg = "test_message"
-    B_, blinding_factor = step1_alice_domain_separated(
+    B_, blinding_factor = step1_alice_deprecated(
         secret_msg,
         blinding_factor=PrivateKey(
             privkey=bytes.fromhex(
@@ -346,15 +345,15 @@ def test_step1_domain_separated():
 
     assert (
         B_.serialize().hex()
-        == "025cc16fe33b953e2ace39653efb3e7a7049711ae1d8a2f7a9108753f1cdea742b"
+        == "02a9acc1e48c25eeeb9289b5031cc57da9fe72f3fe2861d264bdc074209b107ba2"
     )
     assert blinding_factor.private_key == bytes.fromhex(
         "0000000000000000000000000000000000000000000000000000000000000001"
     )
 
 
-def test_step2_domain_separated():
+def test_step2_deprecated():
-    B_, _ = step1_alice_domain_separated(
+    B_, _ = step1_alice_deprecated(
         "test_message",
         blinding_factor=PrivateKey(
             privkey=bytes.fromhex(
@@ -372,16 +371,16 @@ def test_step2_domain_separated():
     C_, e, s = step2_bob(B_, a)
     assert (
         C_.serialize().hex()
-        == "025cc16fe33b953e2ace39653efb3e7a7049711ae1d8a2f7a9108753f1cdea742b"
+        == "02a9acc1e48c25eeeb9289b5031cc57da9fe72f3fe2861d264bdc074209b107ba2"
     )
 
 
-def test_step3_domain_separated():
+def test_step3_deprecated():
     # C = C_ - A.mult(r)
-    # C_ from test_step2
+    # C_ from test_step2_deprecated
     C_ = PublicKey(
         bytes.fromhex(
-            "025cc16fe33b953e2ace39653efb3e7a7049711ae1d8a2f7a9108753f1cdea742b"
+            "02a9acc1e48c25eeeb9289b5031cc57da9fe72f3fe2861d264bdc074209b107ba2"
         ),
         raw=True,
     )
@@ -402,32 +401,52 @@ def test_step3_domain_separated():
 
     assert (
         C.serialize().hex()
-        == "0271bf0d702dbad86cbe0af3ab2bfba70a0338f22728e412d88a830ed0580b9de4"
+        == "03c724d7e6a5443b39ac8acf11f40420adc4f99a02e7cc1b57703d9391f6d129cd"
     )
 
 
-def test_dleq_carol_verify_from_bob_domain_separated():
+def test_dleq_step2_bob_dleq_deprecated():
+    B_, _ = step1_alice_deprecated(
+        "test_message",
+        blinding_factor=PrivateKey(
+            privkey=bytes.fromhex(
+                "0000000000000000000000000000000000000000000000000000000000000001"
+            ),
+            raw=True,
+        ),
+    )
     a = PrivateKey(
         privkey=bytes.fromhex(
             "0000000000000000000000000000000000000000000000000000000000000001"
         ),
         raw=True,
     )
-    A = a.pubkey
+    p_bytes = bytes.fromhex(
-    assert A
-    secret_msg = "test_message"
-    r = PrivateKey(
-        privkey=bytes.fromhex(
         "0000000000000000000000000000000000000000000000000000000000000001"
+    )  # 32 bytes
+    e, s = step2_bob_dleq(B_, a, p_bytes)
+    assert (
+        e.serialize()
+        == "9818e061ee51d5c8edc3342369a554998ff7b4381c8652d724cdf46429be73d9"
+    )
+    assert (
+        s.serialize()
+        == "9818e061ee51d5c8edc3342369a554998ff7b4381c8652d724cdf46429be73da"
+    )  # differs from e only in least significant byte because `a = 0x1`
+
+    # change `a`
+    a = PrivateKey(
+        privkey=bytes.fromhex(
+            "0000000000000000000000000000000000000000000000000000000000001111"
         ),
         raw=True,
     )
-    B_, _ = step1_alice_domain_separated(secret_msg, r)
+    e, s = step2_bob_dleq(B_, a, p_bytes)
-    C_, e, s = step2_bob(B_, a)
+    assert (
-    assert alice_verify_dleq(B_, C_, e, s, A)
+        e.serialize()
-    C = step3_alice(C_, r, A)
+        == "df1984d5c22f7e17afe33b8669f02f530f286ae3b00a1978edaf900f4721f65e"
-
+    )
-    # carol does not know B_ and C_, but she receives C and r from Alice
+    assert (
-    assert carol_verify_dleq_domain_separated(
+        s.serialize()
-        secret_msg=secret_msg, C=C, r=r, e=e, s=s, A=A
+        == "828404170c86f240c50ae0f5fc17bb6b82612d46b355e046d7cd84b0a3c934a0"
     )