# What to do with this specific scenario of a key reuse [duplicate]

I am brand new to the world of cryptogrophy. I am trying to decrypt a many-time-pad. I understand the methodology of using the XOR to get the messages.

C1 XOR C2 = M1 XOR M2

Now my question lies in a specific case. I have about 11 cipher texts with a number down the same index. All of them either have a '2', '3', or '4'. I am completely lost on how to decrypt this key index. If the cipher texts are the same, then it means if I XOR them together I get a ASCII 0 value, I don't know how that helps me. Anything XOR 0, is that anything. So is the message itself contain a integer at that location? Is my key a 0? I doubt that 11 cipher texts would have a number at the exact same spot, seems odd.

How would I go on about getting the key at this specific spot?

• Hint: what if the ciphertexts don't have the same digits; what happens if you xor a text with a '2' with a text with a '3'; how does that differ if instead you xor a '2' with a '4'? – poncho Feb 4 '17 at 16:41
• 2^3=1, 2^4=6. Not sure where it is going. – Maty Feb 4 '17 at 16:53
• So, if you xor two texts, and get a 1 in that position, what can you deduce from that? What if you get a 6? – poncho Feb 4 '17 at 18:34
• The two messages XORed together is a 1 or a 6. – Maty Feb 4 '17 at 19:49