stuff

training/IntroZ3/tasks/chall2_dreamer/test.py

@@ -0,0 +1,51 @@
+
+import random
+import z3
+
+
+def ROL(X, N):
+    if isinstance(X, z3.BitVecRef):
+        return z3.RotateLeft(X,N)
+    else:
+        return ((((X) << (N)) | ((X) >> (64 - (N)))) % (2 ** 64))
+
+
+def ROR(X, N):
+    if isinstance(X, z3.BitVecRef):
+        return z3.RotateRight(X,N)
+    else:
+        return ((((X) >> (N)) | ((X) << (64 - (N)))) % (2 ** 64))
+
+def custom_random(state):
+    NEW_STATE = ROL(state,30) ^ ROR(state,12) ^ ROL(state,42) ^ ROL(state,4) ^ ROR(state,5)
+    return NEW_STATE % 256, NEW_STATE
+
+def get_seed_for_sequence(bytesequence):
+    s = z3.Solver() 
+    base_state = z3.BitVec("base_state", 64)
+    cur_state = base_state
+    for byte in bytesequence:
+        gen_byte, cur_state = custom_random(cur_state)
+        s.add(gen_byte == byte)
+
+    if s.check() != z3.sat:
+        raise RuntimeError()
+
+    m = s.model()
+    return m[base_state].as_long()
+
+
+def gen_sequence(seed, length):
+    r = []
+    cs = seed
+    for _ in range(length):
+        v, cs = custom_random(cs)
+        r.append(v)
+    return bytes(r)
+
+
+test = random.getrandbits(32).to_bytes(4)
+seed = get_seed_for_sequence(test)
+print(seed)
+print(test)
+assert test == gen_sequence(seed, 4)