def guess(list_encrypted):
string_index= int(raw_input("Which string do you want to guess from?"))
string= list_encrypted[string_index]
start_offset= int(raw_input("Enter start offset of guess:"))
end_offset = int(raw_input("Enter end offset of guess:"))
enc= string[start_offset:end_offset]
guess_len= end_offset-start_offset
dec = raw_input("Guessed plain text:")
#Check so you enter the right number of characters while you actually guess stuff and not head scratch where you're going wrong :)
if len(dec) != guess_len:
print "Guess length incorrect.Exiting"
print
sys.exit(0)
#CT xor PT = key based on stream cipher property. Get the key for one string and re-use the key to try and decrypt the rest of the encrypted strings.
key= block.xor(enc, dec)
t4= []
for count,s1 in enumerate(list_encrypted):
t3= s1[start_offset:end_offset]
t4.append(block.xor(key[0:len(t3)],t3))
return t4
def hmac(self, p1):
key = 'teddy'
blocksize = 64
if len(key) > blocksize:
key = sha1(key).hexdigest()
if len(key) < blocksize:
diff = blocksize - len(key)
key = key + '\x00' * diff
o_key_pad = block.xor('\x5c' * blocksize, key)
i_key_pad = block.xor('\x36' * blocksize, key)
m1 = i_key_pad + p1
h_m1 = sha1(m1).hexdigest()
m2 = o_key_pad + h_m1
h_m2 = sha1(m2).hexdigest()
return h_m2
def get_key(decrypted):
t1 = [decrypted[x:x + 16] for x in range(0, len(decrypted), 16)]
s1 = t1[0]
s2 = t1[2]
k1 = []
for i in range(0, 16):
k1.append(block.xor(s1[i], s2[i]))
key = ''.join(k1)
#This is for sanity checking only. Did we recover the key correctly?
key_orig = '0x71e6efcfb44e362b6e14f7abbecf5503'
key_in_binary_orig = binascii.a2b_hex(key_orig[2:])
if key == key_in_binary_orig:
return key
else:
return None
#Importing common crypto module
import block
import common
def ctr_counter_fixed_nonce_encrypt(decoded_input_str, key, nonce, counter):
t1 = nonce + str(counter).zfill(8)
t2 = block.openssl_ecb_encrypt(t1, key)
keystream.append(t2)
return keystream
if __name__ == "__main__":
input_str = 'L77na/nrFsKvynd6HzOoG7GHTLXsTVu9qvY/2syLXzhPweyyMTJULu/6/kXX0KSvoOLSFQ=='
#input_str= 'MDAwMDAwTm93IHRoYXQgdGhlIHBhcnR5IGlzIGp1bXBpbmc='
decoded_input_str = input_str.decode("base64")
blocklen = 16
counter = len(decoded_input_str) / blocklen + 1
key = '71e6efcfb44e362b6e14f7abbecf5503'
nonce = '0' * 8
keystream = []
for i in range(0, counter, 1):
t3 = ctr_counter_fixed_nonce_encrypt(decoded_input_str, key, nonce, i)
keystream = ''.join(t3)
encrypted = block.xor(decoded_input_str, keystream)
decrypted = block.xor(encrypted, keystream)
print decrypted