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Cryptanalysis definition

Cryptanalysis refers to the practice of analyzing codes and ciphers with the aim of deciphering them. Cryptanalysis, also called cryptology, covers the various ways you can decrypt code, or ciphertext, and reveal the hidden message, or plaintext.

See also: brute-force attack, end-to-end encryption

The history of cryptanalysis

Cryptanalysis dates back to ancient Egypt and the use of substitution ciphers to encode messages. The study of cryptanalysis started to develop in the 9th century during the Arab Islamic Golden Age. Al-Kindi, an Arab scholar, is credited with the first successful case of cryptanalysis when he broke a substitution cipher used by the Abbasid Caliphate.

During the Renaissance, cryptanalysis gained more attention with scholars. Leon Battista Alberti is credited with founding Western cryptography. The most famous cryptanalysis effort belongs to a team of British mathematicians led by Alan Turing. They cracked the German Enigma code during World War II.

In the digital age, cryptanalysis, along with cryptography, is used for both offensive and defensive purposes to secure communication, protect computer systems, and improve cybersecurity and intelligence gathering.

Common cryptanalysis techniques

  • A brute-force attack involves trying to decipher a code using every key combination possible.
  • The frequency technique refers to trying to break a cipher by analyzing the symbols or groups of symbols that appear most often.
  • Linear cryptanalysis helps determine the key used by analyzing the relationship between the plaintext, ciphertext, and the key.

Further reading

Ultimate digital security