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-rw-r--r--bip-schnorr/reference.py2
-rw-r--r--bip-schnorr/test-vectors.py26
2 files changed, 27 insertions, 1 deletions
diff --git a/bip-schnorr/reference.py b/bip-schnorr/reference.py
index 79be690..f2a944f 100644
--- a/bip-schnorr/reference.py
+++ b/bip-schnorr/reference.py
@@ -53,6 +53,8 @@ def bytes_from_point(P):
def point_from_bytes(b):
x = int_from_bytes(b)
+ if x >= p:
+ return None
y_sq = (pow(x, 3, p) + 7) % p
y = pow(y_sq, (p + 1) // 4, p)
if pow(y, 2, p) != y_sq:
diff --git a/bip-schnorr/test-vectors.py b/bip-schnorr/test-vectors.py
index da7aec6..195b61b 100644
--- a/bip-schnorr/test-vectors.py
+++ b/bip-schnorr/test-vectors.py
@@ -69,12 +69,14 @@ def vector4():
default_seckey = bytes_from_int(0xB7E151628AED2A6ABF7158809CF4F3C762E7160F38B4DA56A784D9045190CFEF)
default_msg = bytes_from_int(0x243F6A8885A308D313198A2E03707344A4093822299F31D0082EFA98EC4E6C89)
+# Public key is not on the curve
def vector5():
+ # This creates a dummy signature that doesn't have anything to do with the
+ # public key.
seckey = default_seckey
msg = default_msg
sig = schnorr_sign(msg, seckey)
- # Public key is not on the curve
pubkey = bytes_from_int(0xEEFDEA4CDB677750A420FEE807EACF21EB9898AE79B9768766E4FAA04A2D4A34)
assert(point_from_bytes(pubkey) is None)
@@ -185,6 +187,27 @@ def vector13():
return (None, pubkey_gen(seckey), msg, sig, "FALSE", "sig[32:64] is equal to curve order")
+# Test out of range pubkey
+# It's cryptographically impossible to create a test vector that fails if run
+# in an implementation which accepts out of range pubkeys because we can't find
+# a secret key for such a public key and therefore can not create a signature.
+# This test vector just increases test coverage.
+def vector14():
+ # This creates a dummy signature that doesn't have anything to do with the
+ # public key.
+ seckey = default_seckey
+ msg = default_msg
+ sig = schnorr_sign(msg, seckey)
+
+ pubkey_int = p + 1
+ pubkey = bytes_from_int(pubkey_int)
+ assert(point_from_bytes(pubkey) is None)
+ # If an implementation would reduce a given public key modulo p then the
+ # pubkey would be valid
+ assert(point_from_bytes(bytes_from_int(pubkey_int % p)) is not None)
+
+ return (None, pubkey, msg, sig, "FALSE", "public key is not a valid X coordinate because it exceeds the field size")
+
vectors = [
vector0(),
vector1(),
@@ -200,6 +223,7 @@ vectors = [
vector11(),
vector12(),
vector13(),
+ vector14()
]
# Converts the byte strings of a test vector into hex strings