The full question is the following:
Suppose you are told that the one time pad encryption of the message "attack at dawn" is
09e1c5f70a65ac519458e7e53f36 (the plaintext letters are encoded as 8-bit ASCII and the given ciphertext is written in hex). What would be the one time pad encryption of the message "attack at dusk" under the same OTP key?
To me it seems that all you'd have to do is find what the hexadecimal representation of attack at dusk is, add that to attack at dawn message and then use the key to convert attack at dusk to an encrypted value. However, I don't know how to store the hexadecimal value in C++ (or any language for that matter). This is what I thought you would do:
string attackAtDawn = 61747461636b206174206461776e;