New Caesar

new_ceasar/new_caesar.py

@@ -0,0 +1,28 @@
+import string
+
+LOWERCASE_OFFSET = ord("a")
+ALPHABET = string.ascii_lowercase[:16]
+
+def b16_encode(plain):
+	enc = ""
+	for c in plain:
+		binary = "{0:08b}".format(ord(c))
+		enc += ALPHABET[int(binary[:4], 2)]
+		enc += ALPHABET[int(binary[4:], 2)]
+	return enc
+
+def shift(c, k):
+	t1 = ord(c) - LOWERCASE_OFFSET
+	t2 = ord(k) - LOWERCASE_OFFSET
+	return ALPHABET[(t1 + t2) % len(ALPHABET)]
+
+flag = "redacted"
+key = "redacted"
+assert all([k in ALPHABET for k in key])
+assert len(key) == 1
+
+b16 = b16_encode(flag)
+enc = ""
+for i, c in enumerate(b16):
+	enc += shift(c, key[i % len(key)])
+print(enc)

new_ceasar/sol.py

@@ -0,0 +1,30 @@
+#!/home/maxime/.pyvenv/bin/python3
+import string
+
+ALPHABET = string.ascii_lowercase[:16]
+
+def b16_decode(enc):
+    dec = ''
+    assert len(enc) % 2 == 0
+    for i in range(0, len(enc), 2):
+        char = 0
+        msb = ord(enc[i]) - ord('a')
+        lsb = ord(enc[i+1]) - ord('a')
+        char += (msb << 4) + lsb
+        dec += chr(char)
+    return dec
+
+def decode(c, k):
+    t1 = ord(c) - ord('a')
+    t2 = ord(k) - ord('a')
+    return ALPHABET[(t1 - t2) % len(ALPHABET)]
+
+with open("string", 'r') as f:
+    text = f.read().strip()
+    keyset = ALPHABET
+    for key in keyset:
+        decrypted = ''
+        for char in text:
+            decrypted += decode(char, key)
+        print(b16_decode(decrypted))
+

new_ceasar/string

@@ -0,0 +1 @@
+dcebcmebecamcmanaedbacdaanafagapdaaoabaaafdbapdpaaapadanandcafaadbdaapdpandcac