I'm studying encryption in class and we're doing "One-Time-Pad" encryption and I've come across this situation. I want to code $1100$, where my key is $0110$). In my book it says that the cipher is $1010$ - done through binary addition.
but how does that make sense. In a $4$-bit system the numbers can only go to $2^4-1=15$ digits. So $1100+0110=10010$ ($12+6=18$). Am I missing something?