Cryptography referred almost
exclusively to encryption, the process of converting ordinary information
(plain text) into unintelligible gibberish .Decryption is the reverse, moving
from unintelligible
cipher text to
plain text. A cipher (or cypher)
is a pair of algorithms which perform this encryption and the reversing
decryption. The detailed operation of a cipher is controlled both by the
algorithm and, in each instance, by a key. This is a secret parameter
(ideally, known only to the communicants) for a specific message exchange
context. Keys are important, as
ciphers without variable keys are trivially breakable
and therefore less than useful for most purposes. Historically, ciphers were
often used directly for encryption or decryption, without additional procedures
such as authentication or integrity checks.
In colloquial use, the term "code" is often used to mean any
method of encryption or concealment of meaning. However, in cryptography,
code has a more specific meaning; it means the replacement of a unit of plain text
(i.e., a meaningful word or phrase) with a code word (for example, apple pie replaces attack at dawn). Codes are no longer used
in serious cryptography—except incidentally for such things as unit
designations (eg, ''Bronco Flight'' or Operation Overlord) —- since properly
chosen ciphers are both more practical and more secure than even the best
codes, and better adapted to computers as well.
Some use the terms
Cryptography and cryptology interchangeably
in English, while others use cryptography to refer to the use and
practice of cryptographic techniques, and cryptology to refer to the
subject as a field of study.
More abstracts about the cryptography