just for now

week06/easy/client.py

@@ -1,25 +1,44 @@
 import socket
-
+from Crypto.Util.number import getPrime, inverse
+import re
 # Fill in the right target here
-HOST = 'this.is.not.a.valid.domain'  # TODO
-PORT = 0  # TODO
+HOST = 'netsec.net.in.tum.de'  # TODO
+PORT = 20106  # TODO
 
 
 def int_to_bytes(m):
     return m.to_bytes((m.bit_length() + 7) // 8, 'big').decode()
 
+def modular_inverse(p, phi_q):
+    x = inverse(p, phi_q)
+    return x % phi_q
+
+def decrypt_message(encrypted, p, q):
+    phi_q = q - 1
+    d = modular_inverse(p, phi_q)
+    message = pow(encrypted, d, q)
+    return message
+    
+
 
 def get_flag():
     s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
 
     s.connect((HOST, PORT))
     sf = s.makefile('rw')  # we use a file abstraction for the sockets
-
-    message1 = sf.readline().rstrip('\n')
-    # TODO
-
+    m = sf.readline().rstrip('\n')
+    bit_len = int(re.search(r"[0-9]+", m).group())
+    print(f"bit_len is {bit_len}")
+    p = getPrime(bit_len*2)
+    q = getPrime(bit_len*2)
+    sf.write(f'{p};{q}\n')
+    sf.flush()
+    c_m = int(sf.readline().rstrip('\n'))
+    print("C_M: ", c_m)
+    d_m = decrypt_message(c_m, p, q)
     sf.close()
     s.close()
+    print(int_to_bytes(d_m))
 
 
 if __name__ == '__main__':