WHAT IS QUANTUM CRYPTOGRAPHY
Quantum computers, now being reasearched, using quantum effects and qubits instead of bits are capable of doing certain kinds of computation more quickly than conventional computers. A quantum computer can essentially do a very large number of similar computations simultaneously. Conventional ciphers can be completely secure, provided that the sender has access to an encoding key and the reciever has access to the decoding key, but nobody else does. That’s a problem if the communication link isn’t secure – how do the sender and the receiver both get a key without compromising the system? Modern public key systems have different encoding keys and decoding keys so that, for example, the encoding key can be made public, so anyone can encrypt a message, but only the receiver can work out what it said. Only the receiver can work out what the sender said. The only thing that needs to be done is to make sure that the secret key is very hard to work out from the public key. Conventional comput
Quantum cryptography is a form of cryptography which relies on the principles of quantum mechanics to secure data and detect eavesdropping. Like all forms of cryptography, quantum cryptography is potentially breakable, but it is theoretically extremely reliable, which could make it suitable for very sensitive data. Unfortunately, it also requires the possession of some very specialized equipment, which could hinder the spread of quantum cryptography. Cryptography involves the exchange of coded messages. The sender and the recipient have the ability to decode the messages, thereby determining the content. The key and the message are generally sent separately, as one is useless without the other. In the case of quantum cryptography, or quantum key distribution (QKD) as it is sometimes known, quantum mechanics are involved in the generation of the key to make it private and secure. Quantum mechanics is an extremely complex field, but the important thing to know about it in relationship to
Quantum cryptography [BBB92] [Bra93] is a method for secure key exchange over an insecure channel based on the nature of photons. Photons have a polarization, which can be measured in any basis, where a basis consists of two directions orthogonal to each other, as shown in Figure 7.1. Figure 7.1: Bases (click for a larger image) If a photon’s polarization is read in the same basis twice, the polarization will be read correctly and will remain unchanged. If it is read in two different bases, a random answer will be obtained in the second basis, and the polarization in the initial basis will be changed randomly, as shown in Figure 7.2. Figure 7.2: Polarization readings (click for a larger image) The following protocol can be used by Alice and Bob to exchange secret keys. • Alice sends Bob a stream of photons, each with a random polarization, in a random basis. She records the polarizations. • Bob measures each photon in a randomly chosen basis and records the results. • Bob announces, ov
The science of cryptography has existed in one form or another for centuries. Cryptography is the art of encoding and decoding messages for transmission between two parties, while keeping the message secret from unwanted viewers. There are many common implementations of cryptography in use today such as the HTTPS protocol on the Internet. All forms of data encryption and cryptography require a key in some form or another for use in encoding and decoding data. There are even some modern methods of encryption that have been mathematically proven to be unbreakable if they are implemented properly. The inherent problem with any form of cryptography is in the method of key distribution. To date, all forms of message encryption have possessed this major vulnerability. As such, it makes no difference whether a secret message is sent via homing pigeon, a radio transmission, a penciled message on a notepad, or whispering to another, there is no physical way to get a cryptographic key to another
Quantum cryptography is an approach based on quantum physics for secure communications. Unlike traditional cryptography, which employs various mathematical techniques to restrict eavesdroppers from learning the contents of encrypted messages, quantum cryptography is based on the physics of information.
