Cryptography Reference
In-Depth Information
chapter
1
CRYPTOGRAPHY,
CRYPTANALYSIS,
AND CRYPTOLOGY
The term
cryptography
is derived from the Greek
kryptós
(“hidden”) and
gráphein
, (“to write”).
Cryptography was originally the study of the principles
and techniques by which information could be concealed
in ciphers and later revealed by legitimate users employ-
ing the secret key. It now encompasses the whole area of
key-controlled transformations of information into forms
that are either impossible or computationally infeasible
for unauthorized persons to duplicate or undo.
Cryptanalysis (from the Greek
kryptós
and
analýein
, “to
loosen” or “to untie”) is the science and art of recovering
or forging cryptographically secured information without
knowledge of the key. Cryptology (from the Greek
kryptós
and
lógos
, “word”) is often—and mistakenly—considered
a synonym for cryptography and occasionally for crypt-
analysis, but specialists in the field have for years adopted
the convention that cryptology is the more inclusive term,
encompassing both cryptography and cryptanalysis and
including the entire science concerned with data commu-
nication and storage in secure and usually secret form.
Cryptography was initially concerned only with pro-
viding secrecy for written messages, especially in times of
war. Its principles apply equally well, however, to securing
data flowing between computers or data stored in them,
to encrypting facsimile and television signals, to verifying
the identity of participants in e-commerce, and providing
