Custom Encryption

custom_encryption/sol.py

@@ -0,0 +1,24 @@
+#!/home/maxime/.pyvenv/bin/python3
+from pwn import *
+
+with open("enc_flag", 'r') as f:
+    text = f.readlines()
+    a = int(text[0][4:].strip())
+    b = int(text[1][4:].strip())
+    cipher = text[2][11:].replace('[', '').replace(']', '').replace(' ', '').strip().split(',')
+    
+    p = 97
+    g = 31
+    text_key = "trudeau"
+
+    key = pow(g, a*b, p)
+    semi_cipher = ""
+    for i in cipher:
+        i = int(i.strip())
+        semi_cipher += chr(i // (311*key))
+    plaintext = ""
+    for i, char in enumerate(semi_cipher):
+        plaintext += chr(ord(char) ^ ord(text_key[i%len(text_key)]))
+    plaintext = plaintext[::-1]
+    print(plaintext)
+