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Cryptography, or cryptology (from Ancient Greek: κρυπτός, romanized: kryptós "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]
Cryptographic protocols can sometimes be verified formally on an abstract level. When it is done, there is a necessity to formalize the environment in which the protocol operates in order to identify threats.
The following outline is provided as an overview of and topical guide to cryptography: Cryptography (or cryptology) – practice and study of hiding information. Modern cryptography intersects the disciplines of mathematics, computer science, and engineering. Applications of cryptography include ATM cards, computer passwords, and electronic ...
Symmetric key cryptography—compute a ciphertext decodable with the same key used to encode (e.g., AES) Public-key cryptography—compute a ciphertext decodable with a different key used to encode (e.g., RSA) Digital signatures—confirm the author of a message; Mix network—pool communications from many users to anonymize what came from whom
Kerckhoffs viewed cryptography as a rival to, and a better alternative than, steganographic encoding, which was common in the nineteenth century for hiding the meaning of military messages. One problem with encoding schemes is that they rely on humanly-held secrets such as "dictionaries" which disclose for example, the secret meaning of words.
In cryptography, a semantically secure cryptosystem is one where only negligible information about the plaintext can be feasibly extracted from the ciphertext.Specifically, any probabilistic, polynomial-time algorithm (PPTA) that is given the ciphertext of a certain message (taken from any distribution of messages), and the message's length, cannot determine any partial information on the ...
There are a number of standards related to cryptography. Standard algorithms and protocols provide a focus for study; standards for popular applications attract a large amount of cryptanalysis . Encryption standards
Attribute-based encryption is a generalisation of public-key encryption which enables fine grained access control of encrypted data using authorisation policies.The secret key of a user and the ciphertext are dependent upon attributes (e.g. their email address, the country in which they live, or the kind of subscription they have).