Encryption
I INTRODUCTION
Encryption, process of converting messages or data into a form that cannot be read without decrypting or deciphering it. The root of the word encryption—crypt—comes from the Greek word kryptos, meaning “hidden” or “secret.”
The study and practice of encryption and decryption is called the science of cryptography. Scientists who study different ways to protect and ensure the confidentiality, integrity, and authenticity of information are called cryptologists. Cryptologists also engage in cryptanalysis to find ways to break encryption methods. For centuries before the age of electronic communication and computers, individuals, militaries, and other groups coded written information. As electronic forms of communication and information storage and processing have developed, the opportunities to intercept, modify, use, disclose, and read confidential information has grown, and the need for powerful encryption techniques has increased.
II HOW ENCRYPTION WORKS
Encryption uses a step-by-step procedure called an algorithm to convert data or the text of an original message, known as plaintext, into ciphertext, its encrypted form. Cryptographic algorithms normally require a string of characters called a key to encrypt or decrypt data. Those who possess the key and the algorithm can encrypt the plaintext into ciphertext and then decrypt the ciphertext back into plaintext.
Cryptologists engage in an unending competition to create stronger cryptographic techniques and to break them. Many recent cryptography techniques are nearly unbreakable even with the most powerful computers. These systems produce ciphertext that appears to be random characters. These systems resist most existing methods for deciphering back into plaintext. The many different types of new cryptosystems use highly complex mathematical language and resist breaking even though cryptologists may know the techniques used in creating them.
III POPULAR ENCRYPTION SYSTEMS
Three of the most popular cryptography systems used are the Data Encryption Standard (DES), Pretty Good Privacy (PGP), and the Rivest, Shamir, Adleman (RSA) system. DES uses a single key for both encrypting and decrypting. It was developed by International Business Machines Corporation (IBM) and approved by the United States National Institute of Standards and Technology in 1976. The Rivest, Shamir, Adleman (RSA) algorithm is a popular encryption method that uses two keys. It was developed for general use in 1977 and was named for the three computer scientists—Ronald L. Rivest, Adi Shamir, and Leonard Adleman—who originated it. The RSA Data Security Company has been highly successful in licensing its algorithm for others to use.
PGP is an encryption system that also uses two keys. It is based on the RSA algorithm. PGP was invented by software developer Philip Zimmerman and is one of the most common cryptosystems used on the Internet because it is effective, free, and simple to use. PGP is such an effective encryption tool that the United States government sued Zimmerman for releasing it to the public, alleging that making PGP available to enemies of the United States would endanger national security. The lawsuit was dropped, but it is still illegal in some countries to use PGP to communicate with people in other countries.
In the two-key system, also known as the public key system, one key encrypts the information and another, mathematically related key decrypts it. The computer sending an encrypted message uses a chosen private key that is never shared and so is known only to the sender. All computers authorized to receive and decrypt the message are given the matching public key. This method also establishes who sent the message. If a sending computer first encrypts the message with the intended receiver's public key and again with the sender's secret, private key, then the receiving computer may decrypt the message, first using its secret key and then the sender's public key. Using this public-key cryptographic method, the sender and receiver are able to authenticate one another as well as protect the secrecy of the message. Single key methods, in contrast, require great secrecy in conveying a key from sender to recipient.
IV OTHER CRYPTOSYSTEMS
Secure Sockets Layer (SSL), a protocol developed by Netscape Communications Corporation for transmitting private documents via the Internet, and Secure Hypertext Transfer Protocol (S-HTTP), designed to transmit individual messages, also use encryption methods.
The length or complexity of the key (along with the difficulty of the algorithm) usually indicates the effectiveness of the encryption. DES, for example, uses 56 bits in its key to change 8-character message segments into 64-bit segments of ciphertext. In 1997 the National Institute of Standards and Technology began coordinating development of a new encryption system called Advanced Encryption Standard (AES). AES is to replace DES, as it will use a stronger algorithm, based on a 128-bit encryption standard instead of the 64-bit standard that DES now uses. Another advanced encryption system employs the International Data Encryption Algorithm, or IDEA, based on 128-bit segments. The Swiss Federal Institute of Technology developed the IDEA standard in the 1990s. Banks in the United States and several countries in Europe use the IDEA standard for many of their transactions.
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