ed25519: type hints

trezorlib/_ed25519.py

@@ -2,17 +2,20 @@
 # modified for Python 3 by Jochen Hoenicke <hoenicke@gmail.com>
 
 import hashlib
+from typing import Tuple, NewType
+
+Point = NewType("Point", Tuple[int, int])
 
 b = 256
 q = 2 ** 255 - 19
 l = 2 ** 252 + 27742317777372353535851937790883648493
 
 
-def H(m):
+def H(m: bytes) -> bytes:
     return hashlib.sha512(m).digest()
 
 
-def expmod(b, e, m):
+def expmod(b: int, e: int, m: int) -> int:
     if e < 0:
         raise ValueError('negative exponent')
     if e == 0:
@@ -23,7 +26,7 @@ def expmod(b, e, m):
     return t
 
 
-def inv(x):
+def inv(x: int) -> int:
     return expmod(x, q - 2, q)
 
 
@@ -31,7 +34,7 @@ d = -121665 * inv(121666)
 I = expmod(2, (q - 1) >> 2, q)
 
 
-def xrecover(y):
+def xrecover(y: int) -> int:
     xx = (y * y - 1) * inv(d * y * y + 1)
     x = expmod(xx, (q + 3) >> 3, q)
     if (x * x - xx) % q != 0:
@@ -43,22 +46,22 @@ def xrecover(y):
 
 By = 4 * inv(5)
 Bx = xrecover(By)
-B = [Bx % q, By % q]
+B = Point((Bx % q, By % q))
 
 
-def edwards(P, Q):
+def edwards(P: Point, Q: Point) -> Point:
     x1 = P[0]
     y1 = P[1]
     x2 = Q[0]
     y2 = Q[1]
     x3 = (x1 * y2 + x2 * y1) * inv(1 + d * x1 * x2 * y1 * y2)
     y3 = (y1 * y2 + x1 * x2) * inv(1 - d * x1 * x2 * y1 * y2)
-    return [x3 % q, y3 % q]
+    return Point((x3 % q, y3 % q))
 
 
-def scalarmult(P, e):
+def scalarmult(P: Point, e: int) -> Point:
     if e == 0:
-        return [0, 1]
+        return Point((0, 1))
     Q = scalarmult(P, e >> 1)
     Q = edwards(Q, Q)
     if e & 1:
@@ -66,35 +69,35 @@ def scalarmult(P, e):
     return Q
 
 
-def encodeint(y):
+def encodeint(y: int) -> bytes:
     bits = [(y >> i) & 1 for i in range(b)]
     return bytes([sum([bits[i * 8 + j] << j for j in range(8)]) for i in range(b >> 3)])
 
 
-def encodepoint(P):
+def encodepoint(P: Point) -> bytes:
     x = P[0]
     y = P[1]
     bits = [(y >> i) & 1 for i in range(b - 1)] + [x & 1]
     return bytes([sum([bits[i * 8 + j] << j for j in range(8)]) for i in range(b >> 3)])
 
 
-def bit(h, i):
+def bit(h: bytes, i: int) -> int:
     return (h[i >> 3] >> (i & 7)) & 1
 
 
-def publickey(sk):
+def publickey(sk: bytes) -> bytes:
     h = H(sk)
     a = 2 ** (b - 2) + sum(2 ** i * bit(h, i) for i in range(3, b - 2))
     A = scalarmult(B, a)
     return encodepoint(A)
 
 
-def Hint(m):
+def Hint(m: bytes) -> int:
     h = H(m)
     return sum(2 ** i * bit(h, i) for i in range(2 * b))
 
 
-def signature(m, sk, pk):
+def signature(m: bytes, sk: bytes, pk: bytes) -> bytes:
     h = H(sk)
     a = 2 ** (b - 2) + sum(2 ** i * bit(h, i) for i in range(3, b - 2))
     r = Hint(bytes([h[i] for i in range(b >> 3, b >> 2)]) + m)
@@ -103,28 +106,28 @@ def signature(m, sk, pk):
     return encodepoint(R) + encodeint(S)
 
 
-def isoncurve(P):
+def isoncurve(P: Point) -> bool:
     x = P[0]
     y = P[1]
     return (-x * x + y * y - 1 - d * x * x * y * y) % q == 0
 
 
-def decodeint(s):
+def decodeint(s: bytes) -> int:
     return sum(2 ** i * bit(s, i) for i in range(0, b))
 
 
-def decodepoint(s):
+def decodepoint(s: bytes) -> Point:
     y = sum(2 ** i * bit(s, i) for i in range(0, b - 1))
     x = xrecover(y)
     if x & 1 != bit(s, b - 1):
         x = q - x
-    P = [x, y]
+    P = Point((x, y))
     if not isoncurve(P):
         raise ValueError('decoding point that is not on curve')
     return P
 
 
-def checkvalid(s, m, pk):
+def checkvalid(s: bytes, m: bytes, pk: bytes) -> None:
     if len(s) != b >> 2:
         raise ValueError('signature length is wrong')
     if len(pk) != b >> 3: