From 05a0cb2aa02ed4f854b12467949682646ab0bf95 Mon Sep 17 00:00:00 2001
From: Sam Hadow <sam.hadow@inbox.lv>
Date: Sun, 21 Apr 2024 17:48:31 +0200
Subject: [PATCH] correct bits order for x and y + test function for encryption

---
 main.py | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/main.py b/main.py
index e17be25..4e200de 100644
--- a/main.py
+++ b/main.py
@@ -31,6 +31,7 @@ class lfsr(object):
 
 
 def test_lfsr17():
+    print("test lfsr17")
     key = [randint(0, 1) for _ in range(16)] # first 16 bits
     key.append(1)  # prevent initial state from being {0}^17
     taps = [0, 14]
@@ -46,7 +47,7 @@ def test_lfsr17():
             return False
     n_state = len(sorted_states)
     n_state_log = log2(n_state+1)
-    print(f'all {n_state} = 2^({n_state_log})-1 states are different')
+    print(f'all {n_state} = 2^({n_state_log})-1 generated states are different')
     return True
 
 
@@ -66,8 +67,8 @@ def css_encrypt(text, key):
         for _ in range(8):
             x_b2 += str(lfsr17.shift())
             y_b2 += str(lfsr25.shift())
-        x = int(x_b2, 2)
-        y = int(y_b2, 2)
+        x = int(x_b2[::-1], 2)
+        y = int(y_b2[::-1], 2)
 
         z = (x + y + carry) % 256
         carry = 1 if x + y > 255 else 0
@@ -76,8 +77,14 @@ def css_encrypt(text, key):
         cipher_text = (cipher_text << 8) | cipher_byte
     return cipher_text
 
+def test_encrypt():
+    print("test encryption: text 0xffffffffff, key 0x0 ∈ {0, 1}^40")
+    cipher = css_encrypt(0xffffffffff, [0]*40)
+    print(f'cipher: {hex(cipher)}')
+    clear = css_encrypt(cipher, [0]*40)
+    print(f'decrypted: {hex(clear)}')
+    print(f'original text and decrypted message are the same: {clear==0xffffffffff}')
+
 test_lfsr17()
-cipher = css_encrypt(0xffffffffff, [0]*40)
-print(hex(cipher))
-clear = css_encrypt(cipher, [0]*40)
-print(hex(clear))
+print()
+test_encrypt()