refactor b_dhke and add domain separated test

cashu/core/crypto/b_dhke.py

@@ -136,12 +136,17 @@ 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:
-        Y1: PublicKey = hash_to_curve_domain_separated(secret_msg.encode("utf-8"))
-        return C == Y1.mult(a)  # type: ignore
+        return verify_domain_separated(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:
@@ -197,13 +202,26 @@ def carol_verify_dleq(
     valid = alice_verify_dleq(B_, C_, e, s, A)
     # BEGIN: BACKWARDS COMPATIBILITY < 0.15.1
     if not valid:
-        Y1: PublicKey = hash_to_curve_domain_separated(secret_msg.encode("utf-8"))
-        B_1: PublicKey = Y1 + r.pubkey  # type: ignore
-        return alice_verify_dleq(B_1, C_, e, s, A)
+        return carol_verify_dleq_domain_separated(secret_msg, r, C, e, s, A)
     # END: BACKWARDS COMPATIBILITY < 0.15.1
     return valid
 
 
+def carol_verify_dleq_domain_separated(
+    secret_msg: str,
+    r: PrivateKey,
+    C: PublicKey,
+    e: PrivateKey,
+    s: PrivateKey,
+    A: PublicKey,
+) -> bool:
+    Y: PublicKey = hash_to_curve_domain_separated(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)
+    return valid
+
+
 # Below is a test of a simple positive and negative case
 
 # # Alice's keys

tests/test_crypto.py

@@ -1,6 +1,7 @@
 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,
@@ -48,30 +49,6 @@ def test_hash_to_curve_iteration():
     )
 
 
-def test_hash_to_curve_domain_separated():
-    result = hash_to_curve_domain_separated(
-        bytes.fromhex(
-            "0000000000000000000000000000000000000000000000000000000000000000"
-        )
-    )
-    assert (
-        result.serialize().hex()
-        == "024cce997d3b518f739663b757deaec95bcd9473c30a14ac2fd04023a739d1a725"
-    )
-
-
-def test_hash_to_curve_domain_separated_iterative():
-    result = hash_to_curve_domain_separated(
-        bytes.fromhex(
-            "0000000000000000000000000000000000000000000000000000000000000001"
-        )
-    )
-    assert (
-        result.serialize().hex()
-        == "022e7158e11c9506f1aa4248bf531298daa7febd6194f003edcd9b93ade6253acf"
-    )
-
-
 def test_step1():
     secret_msg = "test_message"
     B_, blinding_factor = step1_alice(
@@ -92,26 +69,6 @@ def test_step1():
     )
 
 
-def test_step1_domain_separated():
-    secret_msg = "test_message"
-    B_, blinding_factor = step1_alice_domain_separated(
-        secret_msg,
-        blinding_factor=PrivateKey(
-            privkey=bytes.fromhex(
-                "0000000000000000000000000000000000000000000000000000000000000001"
-            )  # 32 bytes
-        ),
-    )
-
-    assert (
-        B_.serialize().hex()
-        == "025cc16fe33b953e2ace39653efb3e7a7049711ae1d8a2f7a9108753f1cdea742b"
-    )
-    assert blinding_factor.private_key == bytes.fromhex(
-        "0000000000000000000000000000000000000000000000000000000000000001"
-    )
-
-
 def test_step2():
     B_, _ = step1_alice(
         "test_message",
@@ -323,7 +280,7 @@ def test_dleq_alice_direct_verify_dleq():
     assert alice_verify_dleq(B_, C_, e, s, A)
 
 
-def test_dleq_carol_varify_from_bob():
+def test_dleq_carol_verify_from_bob():
     a = PrivateKey(
         privkey=bytes.fromhex(
             "0000000000000000000000000000000000000000000000000000000000000001"
@@ -346,3 +303,77 @@ def test_dleq_carol_varify_from_bob():
 
     # carol does not know B_ and C_, but she receives C and r from Alice
     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
+
+
+def test_hash_to_curve_domain_separated():
+    result = hash_to_curve_domain_separated(
+        bytes.fromhex(
+            "0000000000000000000000000000000000000000000000000000000000000000"
+        )
+    )
+    assert (
+        result.serialize().hex()
+        == "024cce997d3b518f739663b757deaec95bcd9473c30a14ac2fd04023a739d1a725"
+    )
+
+
+def test_hash_to_curve_domain_separated_iterative():
+    result = hash_to_curve_domain_separated(
+        bytes.fromhex(
+            "0000000000000000000000000000000000000000000000000000000000000001"
+        )
+    )
+    assert (
+        result.serialize().hex()
+        == "022e7158e11c9506f1aa4248bf531298daa7febd6194f003edcd9b93ade6253acf"
+    )
+
+
+def test_step1_domain_separated():
+    secret_msg = "test_message"
+    B_, blinding_factor = step1_alice_domain_separated(
+        secret_msg,
+        blinding_factor=PrivateKey(
+            privkey=bytes.fromhex(
+                "0000000000000000000000000000000000000000000000000000000000000001"
+            )  # 32 bytes
+        ),
+    )
+
+    assert (
+        B_.serialize().hex()
+        == "025cc16fe33b953e2ace39653efb3e7a7049711ae1d8a2f7a9108753f1cdea742b"
+    )
+    assert blinding_factor.private_key == bytes.fromhex(
+        "0000000000000000000000000000000000000000000000000000000000000001"
+    )
+
+
+def test_dleq_carol_verify_from_bob_domain_separated():
+    a = PrivateKey(
+        privkey=bytes.fromhex(
+            "0000000000000000000000000000000000000000000000000000000000000001"
+        ),
+        raw=True,
+    )
+    A = a.pubkey
+    assert A
+    secret_msg = "test_message"
+    r = PrivateKey(
+        privkey=bytes.fromhex(
+            "0000000000000000000000000000000000000000000000000000000000000001"
+        ),
+        raw=True,
+    )
+    B_, _ = step1_alice_domain_separated(secret_msg, r)
+    C_, e, s = step2_bob(B_, a)
+    assert alice_verify_dleq(B_, C_, e, s, A)
+    C = step3_alice(C_, r, A)
+
+    # carol does not know B_ and C_, but she receives C and r from Alice
+    assert carol_verify_dleq_domain_separated(
+        secret_msg=secret_msg, C=C, r=r, e=e, s=s, A=A
+    )