Merge pull request #15 from Pharisaeus/improvements

py3 compatibility improvements + some useful algorithms

crypto_commons/generic.py

@@ -1,3 +1,6 @@
+import math
+
+
 def long_range(start, stop, step=1):
     """
     Sequence generator working with python longs
@@ -34,6 +37,8 @@ def long_to_bytes(data):
     :param data: integer
     :return: ascii encoded string
     """
+    if data == 0:
+        return "\0"
     data = int(data)
     data = hex(data).rstrip('L').lstrip('0x')
     if len(data) % 2 == 1:
@@ -250,3 +255,40 @@ def is_printable(data):
     import string
     printable = set(string.printable).union(string.printable.encode('utf-8'))
     return len(set(data).difference(printable)) == 0
+
+
+def baby_steps_giant_steps(a, b, p, N=None):
+    if not N:
+        N = 1 + int(math.sqrt(p))
+    baby_steps = {}
+    baby_step = 1
+    for r in long_range(0, N + 1):
+        baby_steps[baby_step] = r
+        baby_step = baby_step * a % p
+    giant_stride = pow(a, (p - 2) * N, p)
+    giant_step = b
+    for q in long_range(0, N ** 8 + 1):
+        if giant_step in baby_steps:
+            result = q * N + baby_steps[giant_step]
+            return result
+        else:
+            giant_step = giant_step * giant_stride % p
+
+
+def jacobi_symbol(a, n):
+    assert (n > a > 0 and n % 2 == 1)
+    t = 1
+    while a != 0:
+        while a % 2 == 0:
+            a /= 2
+            r = n % 8
+            if r == 3 or r == 5:
+                t = -t
+        a, n = n, a
+        if a % 4 == n % 4 == 3:
+            t = -t
+        a %= n
+    if n == 1:
+        return t
+    else:
+        return 0

crypto_commons/netcat/netcat_commons.py

@@ -10,12 +10,12 @@ def nc(host, port):
 
 
 def receive_until(s, delimiters, break_on_empty=False):
-    all_data = ""
+    all_data = b""
     data = s.recv(1)
     while data not in delimiters:
         all_data += data
         data = s.recv(1)
-        if data == '' and break_on_empty:
+        if not data and break_on_empty:
             return all_data
     return all_data + data
 
@@ -30,13 +30,13 @@ def receive_until_match(s, regex, timeout=None, limit=-1, break_on_empty=False):
     :return: read data
     """
     s.settimeout(timeout)
-    all_data = ""
+    all_data = b""
     i = 0
     try:
-        while re.search(regex, all_data) is None:
+        while re.search(regex, all_data.decode("utf-8")) is None:
             new_char = s.recv(1)
             all_data += new_char
-            if (limit != -1 and i > limit) or (new_char == '' and break_on_empty):
+            if (limit != -1 and i > limit) or (not new_char and break_on_empty):
                 break
             i += 1
     except Exception as e:
@@ -47,7 +47,7 @@ def receive_until_match(s, regex, timeout=None, limit=-1, break_on_empty=False):
 
 
 def send(s, payload):
-    s.sendall(payload + "\n")
+    s.sendall(payload + b"\n")
 
 
 def interactive(s):

crypto_commons/xor/repeating_xor.py

@@ -20,7 +20,7 @@ def interactive_hack(xored, ciphertexts, printable=False):
             err = "Can't break more than a single block at a time! Taking prefix '%s'"
             print(err % potential_plaintext_contents[:ciphertext_len])
 
-        max_missing_bytes = max(map(len, xored)) - len(potential_plaintext_contents)
+        max_missing_bytes = max(map(len, xored)) - len(potential_plaintext_contents) + 1
         for start_position in set(range(max_missing_bytes)).union({0}):
             for index, xored_ciphertext in enumerate(xored):
                 number_of_ciphertexts = len(ciphertexts)