Cryptography is where security engineering meet mathematics. It provides us with the tools that underlie most modern security protocols. It is probably the key enabling technology for protecting distributed systems, yet it is surprisingly hard to do it right.
Cryptography is the science and art of designing cryptographic ciphers.
Cryptanalysis is the science and art of breaking them.
Cryptology is the study of both.
This domain includes:
- Encryption concepts
- Digital signatures
- Cryptanalytic attacks
- Public Key Infrastructure (PKI)
- Information hiding alternatives
Here are some videos which explains Cryptography well:
The most well known and developed application of quantum cryptography is quantum key distribution (QKD). QKD describes the process of using quantum communication to establish a shared key between two parties (usually called Alice and Bob) without a third party (Eve) learning anything about that key, even if Eve can eavesdrop on all communication between Alice and Bob. This is achieved by Alice encoding the bits of the key as quantum data and sending them to Bob; if Eve tries to learn these bits, the messages will be disturbed and Alice and Bob will notice. The key is then typically used for encrypted communication.
The security of QKD can be proven mathematically without imposing any restrictions on the abilities of an eavesdropper, something not possible with classical key distribution. This is usually described as "unconditional security", although there are some minimal assumptions required including that the laws of quantum mechanics apply and that Alice and Bob are able to authenticate each other, i.e. Eve should not be able to impersonate Alice or Bob as otherwise a man-in-the-middle attack would be possible.
Professor Artur Erket
Tokyo QKD 2010: Introduction to Quantum Cryptography
Scientific American :Quantum Entanglement Lab