noun (n)

• the science of analyzing and deciphering codes and ciphers and cryptograms(noun.cognition)

  Synonym:
  cryptanalysis, cryptanalytics, cryptology
  

  source: wordnet30
• act of writing in code or cipher(noun.act)

  Synonym:
  coding, secret writing, steganography
  

  source: wordnet30
• The act or art of writing in secret characters; also, secret characters, or cipher.(noun)

  source: webster1913