The Collaborative International Dictionary of English v.0.48:

Cryptography \Cryp*tog"ra*phy\ (-f?), n. [Cf. F. cryptographie.]
   1. The act or art of writing in code or secret characters;
      also, secret characters, codes or ciphers, or messages
      written in a secret code.
      [1913 Webster +PJC]

   2. The science which studies methods for encoding messages so
      that they can be read only by a person who knows the
      secret information required for decoding, called the key;
      it includes cryptanalysis, the science of decoding
      encrypted messages without possessing the proper key, and
      has several other branches; see for example
      steganography.
      [PJC]

WordNet (r) 3.0 (2006):

cryptography
    n 1: the science of analyzing and deciphering codes and ciphers
         and cryptograms [syn: cryptanalysis, cryptanalytics,
         cryptography, cryptology]
    2: act of writing in code or cipher [syn: cryptography,
       coding, secret writing, steganography]

Moby Thesaurus II by Grady Ward, 1.0:

48 Moby Thesaurus words for "cryptography":
   cipher, code, coded message, coup de plume, criticism,
   cryptanalysis, cryptoanalysis, cryptoanalytics, cryptogram,
   cryptograph, cryptographer, cryptology, diagnostics, engrossment,
   epigraphy, exegetics, hermeneutics, ink spilling, inkslinging,
   inscription, invisible ink, lettering, lexicography,
   literary criticism, macrography, metoposcopy, micrography,
   oneirology, paleography, pathognomy, pen, pen-and-ink,
   pencil driving, physiognomics, physiognomy, scrivenery, scrivening,
   secret language, secret writing, semeiology, semeiotics,
   sympathetic ink, symptomatology, textual criticism, tropology,
   typewriting, typing, writing



The Free On-line Dictionary of Computing (30 December 2018):

cryptography

    The practise and study of encryption and
   decryption - encoding data so that it can only be decoded by
   specific individuals.  A system for encrypting and decrypting
   data is a cryptosystem.  These usually involve an algorithm
   for combining the original data ("plaintext") with one or
   more "keys" - numbers or strings of characters known only to
   the sender and/or recipient.  The resulting output is known as
   "ciphertext".

   The security of a cryptosystem usually depends on the secrecy
   of (some of) the keys rather than with the supposed secrecy of
   the algorithm.  A strong cryptosystem has a large range of
   possible keys so that it is not possible to just try all
   possible keys (a "brute force" approach).  A strong
   cryptosystem will produce ciphertext which appears random to
   all standard statistical tests.  A strong cryptosystem will
   resist all known previous methods for breaking codes
   ("cryptanalysis").

   See also cryptology, public-key encryption, RSA.

   Usenet newsgroups: news:sci.crypt,
   news:sci.crypt.research.

   FAQ MIT
   (ftp://rtfm.mit.edu/pub/usenet/news.answers/cryptography-faq/).

   Cryptography glossary
   (http://io.com/~ritter/GLOSSARY.HTM#BruteForceAttack).

   RSA cryptography glossary
   (http://rsasecurity.com/rsalabs/faq/glossary.html).

   Cryptography, PGP, and Your Privacy
   (http://draco.centerline.com:8080/~franl/crypto.html).

   (2000-01-16)