Finish Challenge 64 RSA parity oracle

data/set6c46.py

@@ -0,0 +1,42 @@
+from math import ceil, floor, log
+
+e = 17
+d = 413
+n = 3233
+m = 65;
+
+def crypt(m):
+    return pow(m, e, n)
+
+def clear(c):
+    return pow(c, d, n)
+
+def oracle(c):
+    return clear(c) % 2 == 0
+
+def double(c):
+    return (c * crypt(2)) % n
+
+def solve(c, lower, upper):
+    div = 1
+    for i in range(int(log(n, 2)) + 1):
+        print(f"{i=} {lower=} {upper=} {div=}")
+        div = div * 2
+        lower = lower * 2
+        upper = upper * 2
+        new = (lower + upper) >> 1
+        c = double(c)
+        if oracle(c):
+            upper = new
+        else:
+            lower = new
+    return upper * n // div
+
+for m in range(2, n - 1):
+    c = crypt(m)
+    r = solve(c, 0, 1)
+    print(f"{m=} {c=} {r=}")
+    assert(r == m)
+
+
+