continued reorganisation

bcrypter/hash/rev.py

@@ -0,0 +1,59 @@
+'''
+This file reverse engineers and reconstructs the original 
+"bcrypt" hash function for the CTF (stored in bcrypt/hash.py).
+This reconstructs implements, namely, precomputation of tables
+of values in the hashing. Allowing bulk computation of hashes
+to be significantly faster.
+'''
+
+from array import array
+from typing import Optional
+
+# Constants
+H = 18446744073709551614
+K = 59275109328752
+M = 2**64
+
+def Rjb(j: int, b: int) -> int:
+    return b << j**2
+
+def Rb(b: int) -> int:
+    Rb = 0
+    for j in range(8):
+        Rb ^= Rjb(j, b) 
+    return Rb
+
+'''
+Reconstructed implementation of the "bcrypt" hash function by bpaul.
+NOTE: An optional precomputed R_table is permitted as an arguement.
+'''
+def bcrypt(x: bytes, R_table: Optional[dict[int, int]] = None) -> int:
+    h = -2
+    for i, b in enumerate(x):
+        R = R_table[b] if R_table is not None else Rb(b)
+        h = h**2 * (b+1) + ((K * (i+1)) ^ R)
+        h %= M
+    return h % M
+
+'''
+Returns a hashmap (python dictionary) of b -> R(b)
+for all b such that: min <= b <= max
+'''
+def calc_R_map(min: int = 0,
+               max: int = 255) -> dict[int, int]:
+    R_map = {}
+    # b from min to max (inclusive)
+    for b in range(min, max+1):
+        R_map[b] = Rb(b)
+    return R_map
+
+'''
+Same as calc_R_map() but using an array not a hashmap.
+'''
+def calc_R_array(min: int = 0,
+                 max: int = 255) -> array.array[int]:
+    R_array = array('i', [0]*(max-min))
+    # b from min to max (inclusive)
+    for b in range(min, max+1):
+        R_array[b-min] = Rb(b)
+    return R_array