Editing Theoretical computer science (section)

===Cryptography===
{{main|Cryptography}}
[[Cryptography]]  is the practice and study of techniques for [[secure communication]] in the presence of third parties (called [[adversary (cryptography)|adversaries]]).<ref name="rivest90">{{cite book|first=Ronald L.|last=Rivest|author-link=Ron Rivest|editor=J. Van Leeuwen|title=Handbook of Theoretical Computer Science|chapter=Cryptology|volume=1|publisher=Elsevier|year=1990}}</ref> More generally, it is about constructing and analyzing [[communications protocol|protocol]]s that overcome the influence of adversaries<ref name="modern-crypto">{{Cite book|first1=Mihir|last1=Bellare|first2=Phillip|last2=Rogaway|title=Introduction to Modern Cryptography|chapter=Introduction|page=10|date=21 September 2005}}</ref> and that are related to various aspects in [[information security]] such as data [[confidentiality]], [[data integrity]], [[authentication]], and [[non-repudiation]].<ref name="hac">{{cite book |first1=A. J. |last1=Menezes |first2=P. C. |last2=van Oorschot |first3=S. A. |last3=Vanstone |url=https://archive.org/details/handbookofapplie0000mene |title=Handbook of Applied Cryptography |isbn=978-0-8493-8523-0 |year=1997 |publisher=Taylor & Francis }}</ref> Modern cryptography intersects the disciplines of [[mathematics]], [[computer science]], and [[electrical engineering]]. Applications of cryptography include [[automated teller machine|ATM cards]], [[password|computer passwords]], and [[electronic commerce]].

Modern cryptography is heavily based on mathematical theory and computer science practice; cryptographic algorithms are designed around [[computational hardness assumption]]s, making such algorithms hard to break in practice by any adversary. It is theoretically possible to break such a system, but it is infeasible to do so by any known practical means. These schemes are therefore termed computationally secure; theoretical advances, e.g., improvements in [[integer factorization]] algorithms, and faster computing technology require these solutions to be continually adapted. There exist [[Information theoretic security|information-theoretically secure]] schemes that {{not a typo|provably}} cannot be broken even with unlimited computing power—an example is the [[one-time pad]]—but these schemes are more difficult to implement than the best theoretically breakable but computationally secure mechanisms.