We have introduced the basic notions of communication theory and cryptography both for classical and quantum physics. We have introduced the respective basic units of information – the bit and the qubit. Following the Kerckhoffs’ principle we have seen that the availability of secret key is sufficient to establish secure communication. We have seen how the BB84 quantum cryptography enables two distant parties to establish such a secret key, and how this relies on the quantum physical principle of no measurement without disturbance. Finally, we have addressed some of the technical issues and future challenges of quantum cryptography.