Cryptography

Lorenz cipher machine twelve rotors with mechanism
Lorenz cipher machine, used in World War II to encrypt communications of the German High Command

Cryptography, or cryptology (from Ancient Greek: κρυπτός, romanizedkryptós "hidden, secret"; and γράφειν graphein, "to write", or -λογία -logia, "study", respectively[1]), is the practice and study of techniques for secure communication in the presence of adversarial behavior.[2] More generally, cryptography is about constructing and analyzing protocols that prevent third parties or the public from reading private messages.[3] Modern cryptography exists at the intersection of the disciplines of mathematics, computer science, information security, electrical engineering, digital signal processing, physics, and others.[4] Core concepts related to information security (data confidentiality, data integrity, authentication, and non-repudiation) are also central to cryptography.[5] Practical applications of cryptography include electronic commerce, chip-based payment cards, digital currencies, computer passwords, and military communications.

Cryptography prior to the modern age was effectively synonymous with encryption, converting readable information (plaintext) to unintelligible nonsense text (ciphertext), which can only be read by reversing the process (decryption). The sender of an encrypted (coded) message shares the decryption (decoding) technique only with the intended recipients to preclude access from adversaries. The cryptography literature often uses the names "Alice" (or "A") for the sender, "Bob" (or "B") for the intended recipient, and "Eve" (or "E") for the eavesdropping adversary.[6] Since the development of rotor cipher machines in World War I and the advent of computers in World War II, cryptography methods have become increasingly complex and their applications more varied.

Modern cryptography is heavily based on mathematical theory and computer science practice; cryptographic algorithms are designed around computational hardness assumptions, making such algorithms hard to break in actual practice by any adversary. While it is theoretically possible to break into a well-designed system, it is infeasible in actual practice to do so. Such schemes, if well designed, are therefore termed "computationally secure". Theoretical advances (e.g., improvements in integer factorization algorithms) and faster computing technology require these designs to be continually reevaluated and, if necessary, adapted. Information-theoretically secure schemes that provably cannot be broken even with unlimited computing power, such as the one-time pad, are much more difficult to use in practice than the best theoretically breakable but computationally secure schemes.

The growth of cryptographic technology has raised a number of legal issues in the Information Age. Cryptography's potential for use as a tool for espionage and sedition has led many governments to classify it as a weapon and to limit or even prohibit its use and export.[7] In some jurisdictions where the use of cryptography is legal, laws permit investigators to compel the disclosure of encryption keys for documents relevant to an investigation.[8][9] Cryptography also plays a major role in digital rights management and copyright infringement disputes with regard to digital media.[10]

  1. ^ Liddell, Henry George; Scott, Robert; Jones, Henry Stuart; McKenzie, Roderick (1984). A Greek-English Lexicon. Oxford University Press.
  2. ^ Rivest, Ronald L. (1990). "Cryptography". In J. Van Leeuwen (ed.). Handbook of Theoretical Computer Science. Vol. 1. Elsevier.
  3. ^ Bellare, Mihir; Rogaway, Phillip (21 September 2005). "Introduction". Introduction to Modern Cryptography. p. 10.
  4. ^ Sadkhan, Sattar B. (December 2013). "Key note lecture multidisciplinary in cryptology and information security". 2013 International Conference on Electrical Communication, Computer, Power, and Control Engineering (ICECCPCE). pp. 1–2. doi:10.1109/ICECCPCE.2013.6998773. ISBN 978-1-4799-5633-3. S2CID 22378547. Archived from the original on 27 August 2022. Retrieved 20 September 2022.
  5. ^ Menezes, A.J.; van Oorschot, P.C.; Vanstone, S.A. (1997). Handbook of Applied Cryptography. Taylor & Francis. ISBN 978-0-8493-8523-0.
  6. ^ Biggs, Norman (2008). Codes: An introduction to Information Communication and Cryptography. Springer. p. 171.
  7. ^ Cite error: The named reference cryptolaw was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference UK law was invoked but never defined (see the help page).
  9. ^ Ranger, Steve (24 March 2015). "The undercover war on your internet secrets: How online surveillance cracked our trust in the web". TechRepublic. Archived from the original on 12 June 2016. Retrieved 12 June 2016.
  10. ^ Cite error: The named reference AACS was invoked but never defined (see the help page).

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