update readme

crypto/XMASSpirit/README.md

@@ -24,7 +24,7 @@ HTB{4ff1n3_c1ph3r_15_51mpl3_m47h5}
 - So it's possible to attack the encryption by iterating and trying to create a	pair (a, b) that matches the entire encrypted pdf header.
 
 ```python
-def get_factors(ct, n=256):
+def get_factors(ct:bytes, n:int=256) -> (int, int):
     ''' find a and b for n and ct '''
     # first generate a list of all numbers without common divisor with 256
     nogcds = [ x for x in range(1, n) if gcd(x, n) == 1 ]
@@ -43,7 +43,7 @@ def get_factors(ct, n=256):
 - When the factors are found, simply create a lookup table of all values and substitute each byte in the ciphertext.
 
 ```python
-def decrypt(ct):
+def decrypt(ct:bytes) -> bytes:
     ''' decrypt the file using the lookup table '''
     res = b''
     for byte in ct: