ENCRYPTION
Encryption or information scrambling technology is a simple XOR algorithm with a procedure that involves a mathematical transformation of information into scrambled data, called ‘Cipher text’—a set of rules that specify the kind of arithmetic operations used for specific sets of data. The encryption algorithm uses a key, which is a big number associated with a password and consists of long, randomly chosen strings of bits, to convert plain text into cipher text with strings of characters or numbers. The encryption technology is a supplier of software protection devices allowing software to be protected against unlicensed use. This technology can provide a secure communication channel, despite the insecure network infrastructure, when data passes through shared systems among a group of people who may have access to the data. In these situations, data should be encrypted to prevent any unintended modifications.
Encryption can be divided into two categories, block encryption and data-stream encryption. In block encryption, the plaintext is segmented into blocks of fixed size, which each then is encrypted separately. In this way, a plaintext block would be encrypted into the same cipher text block. Data-stream encryption on contrast has no fixed size.
Modern encryption techniques are based on mathematical theories and encrypt a message by altering it in some reversible way; for example, a W becomes 23 and an F becomes 7. the message is then changed by adding two, for example, to each number and moving each letter two places up the alphabet; for instance, 2 would become B and Y would become A. this conversion technique creates a cipher text that is only decodable by an expert in this technology. The cipher text can become more complex by converting another piece of text into numeric form and adding it to the secret code. This added text is called a ‘key.’ In modern systems, the key is a number with at least 64 bits or about 20 digits. The more bit strength you have, 128 bits or about 40 digits, the more complex your password key can be, hence the more secure your documents are. For example, 56 bit encryption uses a 56 bit key, which allows 72 quadrillion possible combinations, yet
128 bit encryptions are 4.7 sextillion times more difficult to track. The security of these systems is based on the fact that there are various keys and it’s difficult to find which one matches your message.
Presently the most secure form of encryption is one-time pad, which refers to the practice of using a pad of hundreds of sheets of paper containing a random sequence of letters. In this case, the sender has one pad and the receiver has a copy of it and one copy is used for encryption, the other is used for decryption; both copies are destroyed after the message is deciphered (one-time pad). There are public and private keys, which are the two cryptographic methods that are applied to computer security problems. Quantum cryptography is a new type of encryption that uses particles of light (photons) to establish random numbers. Cryptography creates unbreakable codes that involve the laws of quantum physics; physical states such as photon polarization can be used as a key for encoding information, since an intruder can’t discover a cryptographic key based on particle state information according to Heisenberg uncertainty principle. In private-key encryption, the sender and receiver of information share a key that’s both used for encryption and decryption. In public key encryption two different mathematically related keys are used to encrypt and decrypt data. The security of a cryptogram depends on the

key’s length, if the key is shorter than the encrypted message, some information about the message can be discovered. To avoid such eavesdropping, cryptosystems such as the
Vernam cipher (the key is as long as the message) have been produced to hide the messages. One of the most commonly used ciphers is the Data Encryption Standard. One of the biggest problems of cryptography is the management of private and public keys.
Private encryption keys must be protected against theft, recoverable and matched with encrypted data.
Physicists are getting close to find a more secure method of encryption. This new method, unlike the previous ciphers, is theoretically unbreakable rather than just practically unbreakable. The first quantum technology out to the market will have current public-key systems and security will be provided through changing the keys up to a speed of 4 times per second, so that hackers will have to crack multiple AES codes. Today’s quantum key distribution uses an emitter (based on a single photon) for fiber-optic networks. The emitters have a speed of 1Kb/s and are limited to less than 100 Km, but they are completely secure. Currently experimental messages encrypted are being sent over tens of kilometers of optical fibers and received securely. A few years ago the first quantum cryptography machine which can send encrypted messages through air over dozens of kilometers was unveiled at the Los Alames National Laboratory in New
Mexico last year (2003). Magiq Technologies Inc. used quantum techniques to create a
BB84 encryption key code that has a key that can never be cracked.