All modern cryptography is based on the use of algorithms to scramble (encrypt) the original message, called plaintext, into unintelligible babble, called ciphertext. The operation of the algorithm requires the use of a key. Until 1976 the algorithms were symmetric, that is, the key used to encrypt the plaintext was the same as the key used to decrypt the ciphertext. In 1977 the asymmetric or public key algorithm was introduced by the American mathematicians W. Diffie and M. E. Hellman. This algorithm requires two keys, an unguarded public key used to encrypt the plaintext and a guarded private key used for decryption of the ciphertext; the two keys are mathematically related but cannot be deduced from one another. The advantages of asymmetric algorithms are that compromising one of the keys is not sufficient for breaking the cipher and fewer unique keys must be generated.

In 1977 the Data Encryption Standard (DES), a symmetric algorithm, was adopted in the United States as a federal standard. DES and the International Data Encryption Algorithm (IDEA) are the two most commonly used symmetric techniques. The most common asymmetric technique is the RSA algorithm, named after Ronald Rivest, Adi Shami, and Len Adleman, who invented it while at the Massachusetts Institute of Technology in 1977. Other commonly used encryption algorithms include Pretty Good Privacy (PGP), Secure Sockets Layer (SSL), and Secure Hypertext Transfer Protocol (S-HTTP). The National Institute of Standards and Technology (NIST) is working with industry and the cryptographic community to develop the Advanced Encryption Standard (AES), a mutually acceptable algorithm that will protect sensitive government information and will be used by industry on a voluntary basis.

Data encryption is regarded by the U.S. government as a national-security issue because it can interfere with intelligence gathering—therefore, it is subject to export controls, which in turn make it difficult for U.S. companies to function competitively in the international marketplace. To resolve this dilemma, the federal government in 1993 proposed key escrow encryption, an approach, embodied in an electronic device called a "Clipper chip," that makes broadly available a purportedly unbreakable encryption technique (although the code was broken by researchers in 1995) with keys to unlock the information held in escrow for national security and law-enforcement purposes by the federal government. This approach, however, has been unacceptable to civil libertarians and to the international community. In 1994 the Clipper algorithm (called Skipjack) was specified in the Escrow Encryption Standard (EES), a voluntary federal standard for encryption of voice, facsimile (fax), and data communications over ordinary telephone lines. A subsequent compromise escrow scheme intended to create a standard for data encryption that balanced the needs of national security, law enforcement, and personal freedom was rejected in 1995; a compromise proposed in 1999 was also controversial.

Acquisition, recording, organization, retrieval, display, and dissemination of information. Today the term usually refers to computer-based operations. Information processing consists of locating and capturing information, using software to manipulate it into a desired form, and outputting the data. An Internet search engine is an example of an information-processing tool, as is any sophisticated information-retrieval system. Seealso data processing.

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Process of disguising information as “ciphertext,” or data that will be unintelligible to an unauthorized person. Decryption is the process of converting ciphertext back into its original format, sometimes called plaintext (see cryptography). Computers encrypt data by applying an algorithm to a block of data. A personal key known only to the message's transmitter and intended receiver is used to control the encryption. Well-designed keys are almost impregnable. A key 16 characters long selected at random from 256 ASCII characters could take far longer than the 15-billion-year age of the universe to decode, assuming the perpetrator attempted 100 million different key combinations per second. Symmetric encryption requires the same key for both encryption and decryption. Asymmetric encryption, or public-key cryptography, requires a pair of keys, one for encryption and one for decryption.

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Process of reducing the amount of data needed for storage or transmission of a given piece of information (text, graphics, video, sound, etc.), typically by use of encoding techniques. Data compression is characterized as either lossy or lossless depending on whether some data is discarded or not, respectively. Lossless compression scans the data for repetitive sequences or regions and replaces them with a single “token.” For example, every occurrence of the word the or region with the colour red might be converted to $. ZIP and GIF are the most common lossless formats for text and graphics, respectively. Lossy compression is frequently used for photographs, video, and sound files where the loss of some detail is generally unnoticeable. JPEG and MPEG (see MP3) are the most common lossy formats.

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Collection of data or information organized for rapid search and retrieval, especially by a computer. Databases are structured to facilitate storage, retrieval, modification, and deletion of data in conjunction with various data-processing operations. A database consists of a file or set of files that can be broken down into records, each of which consists of one or more fields. Fields are the basic units of data storage. Users retrieve database information primarily through queries. Using keywords and sorting commands, users can rapidly search, rearrange, group, and select the field in many records to retrieve or create reports on particular aggregates of data according to the rules of the database management system being used.

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