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Longman Dictionary of Contemporary English
▪ And anyone communicating by quantum cryptography also would have a sure way to spot spies.
▪ Clearly, one advantage of public-key cryptography is that no one can figure out the private key from the corresponding public key.
▪ Furthermore, public-key cryptography can be used for sender authentication, known as digital signatures.
▪ Public-Key Cryptography A more powerful form of cryptography involves the use of public keys.
▪ Secret-Key Cryptography Secret-key cryptography involves the use of a shared key for both encryption by the transmitter and decryption by the receiver.
▪ The potential commercial and military applications of quantum cryptography are breathtaking.
▪ These are the basics of single-key cryptography.
▪ Zimmermann was the target of a federal investigation for his role in creating a publicly available cryptography program called Pretty Good Privacy.
The Collaborative International Dictionary

Cryptography \Cryp*tog"ra*phy\ (-f?), n. [Cf. F. cryptographie.]

  1. The act or art of writing in code or secret characters; also, secret characters, codes or ciphers, or messages written in a secret code.

  2. the science which studies methods for encoding messages so that they can be read only by a person who knows the secret information required for decoding, called the key; it includes cryptanalysis, the science of decoding encrypted messages without possessing the proper key.

Douglas Harper's Etymology Dictionary

1650s, from French cryptographie or directly from Modern Latin cryptographia, from Greek kryptos "hidden" (see crypt) + -graphy. Related: Cryptograph; cryptographer.


n. The discipline concerned with communication security (eg, confidentiality of messages, integrity of messages, sender authentication, non-repudiation of messages, and many other related issues), regardless of the used medium such as pencil and paper or computers.

  1. n. the science of analyzing and deciphering codes and ciphers and cryptograms [syn: cryptanalysis, cryptanalytics, cryptology]

  2. act of writing in code or cipher [syn: coding, secret writing]


Cryptography or cryptology (from Greek kryptós, "hidden, secret"; and graphein, "writing", or -logia, "study", respectively) is the practice and study of techniques for secure communication in the presence of third parties called adversaries. More generally, cryptography is about constructing and analyzing protocols that prevent third parties or the public from reading private messages; various aspects in information security such as data confidentiality, data integrity, authentication, and non-repudiation are central to modern cryptography. Modern cryptography exists at the intersection of the disciplines of mathematics, computer science, and electrical engineering. Applications of cryptography include ATM cards, computer passwords, and electronic commerce.

Cryptography prior to the modern age was effectively synonymous with encryption, the conversion of information from a readable state to apparent nonsense. The originator of an encrypted message (Alice) shared the decoding technique needed to recover the original information only with intended recipients (Bob), thereby precluding unwanted persons (Eve) from doing the same. The cryptography literature often uses Alice ("A") for the sender, Bob ("B") for the intended recipient, and Eve (" eavesdropper") for the adversary. Since the development of rotor cipher machines in World War I and the advent of computers in World War II, the methods used to carry out cryptology have become increasingly complex and its application more widespread.

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 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-theoretically secure schemes that 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.

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. 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. Cryptography also plays a major role in digital rights management and copyright infringement of digital media.

Usage examples of "cryptography".

His success cemented his attachment to cryptanalysis, and he followed this demonstration of the low estate of high-level cryptography with a 100-page memorandum on the solution of American diplomatic codes.

Gruppen II and III into Hauptgruppe a for cryptography, Gruppen IV and V into Hauptgruppe b for cryptanalysis, each with its own head who reported to Kettler.

Instead of interesting the readers, it evidently destroyed even the slightest desire to read the epitaphs, for soon after the funerary cryptography was begun, it was abandoned.

This list encompassed, for the first time in cryptography, both transposition and substitution ciphers.

They looked instead to that neglected child of cryptography, the cipher.

More ideas came from army officers who had studied cryptography in the courses in signal communication that the national military academies, such as St.

Moreover, cryptography still functions through a hierarchy and employs a multitude of special systems.

The telegraph thereby furnished cryptography with the structure and the content that it still has.

The sentence is pregnant with most of the requirements that have come to be demanded of systems of military cryptography, requirements such as simplicity, reliability, rapidity, and so on.

He was on the side of the angels, but a practical field cipher that is unbreakable was not possible in his day, nor is it today, and so military cryptography has settled for field ciphers that delay but do not defeat cryptanalysis.

Kerckhoffs merely published his perceptions of the problems facing post-telegraph cryptography and his prescriptions for resolving them, he would have assured a place for himself in the pantheon of cryptology.

The army at the same time prepared, through a Military Cryptography Commission, for the solution of enciphered German radio messages.

Kerckhoffs accurately regarded it as an auxiliary to cryptography, a means to the end of perfecting military codes and ciphers.

He freed a fundamental process in cryptography from the shackles of time and error.

His great contribution was to bring to cryptography the automation that had benefited mankind so much in so many fields of endeavor.