Cryptanalysis

From Wikipedia, the free encyclopedia

Close-up of the rotors in a Fialka cipher machine

Cryptanalysis (from the Greek kryptós, "hidden", and analýein, "to loosen" or "to untie") is the art and science of analyzing information systems in order to study the hidden aspects of the systems.^[1] Cryptanalysis is used to breach cryptographic security systems and gain access to the contents of encrypted messages, even if the cryptographic key is unknown.
In addition to mathematical analysis of cryptographic algorithms, cryptanalysis also includes the study of side-channel attacks that do not target weaknesses in the cryptographic algorithms themselves, but instead exploit weaknesses in their implementation.
Even though the goal has been the same, the methods and techniques of cryptanalysis have changed drastically through the history of cryptography, adapting to increasing cryptographic complexity, ranging from the pen-and-paper methods of the past, through machines like Bombes and Colossus computers at Bletchley Park in World War II, to the mathematically advanced computerized schemes of the present. Methods for breaking modern cryptosystems often involve solving carefully constructed problems in pure mathematics, the best-known being integer factorization.

Contents

• 1 Overview
  • 1.1 Amount of information available to the attacker
  • 1.2 Computational resources required
  • 1.3 Partial breaks
• 2 History of cryptanalysis
  • 2.1 Classical ciphers
  • 2.2 Ciphers from World War I and World War II
    • 2.2.1 Indicator
    • 2.2.2 Depth
  • 2.3 The development of modern cryptography
• 3 Cryptanalysis of symmetric ciphers
• 4 Cryptanalysis of asymmetric ciphers
• 5 Attacking cryptographic hash systems
• 6 Side-channel attacks
• 7 Quantum computing applications for cryptanalysis
• 8 See also
  • 8.1 Historic cryptanalysts
• 9 References
  • 9.1 Notes
  • 9.2 Bibliography
• 10 Further reading
• 11 External links

Overview

Given some encrypted data ("ciphertext"), the goal of the cryptanalyst is to gain as much information as possible about the original, unencrypted data ("plaintext").