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Topics In Cryptography
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 commerce. Essence of cryptography * Cryptographer * Encryption/decryption * Cryptographic key * Cipher * Ciphertext * Plaintext * Code * Tabula recta * Alice and Bob Uses of cryptographic techniques * Commitment schemes * Secure multiparty computation * Electronic voting * Authentication * Digital signatures * Crypto systems * Dining cryptographers problem * Anonymous remailer * Pseudonymity * Onion routing * Digital currency * Secret sharing * Indistinguishability obfuscation Branches of cryptography * Multivariate cryptography * Post-quantum cryptography * Quantum cryptography * Steganography * Visual cryptography * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Cipher
In cryptography, a cipher (or cypher) is an algorithm for performing encryption or decryption—a series of well-defined steps that can be followed as a procedure. An alternative, less common term is ''encipherment''. To encipher or encode is to convert information into cipher or code. In common parlance, "cipher" is synonymous with "code (cryptography), code", as they are both a set of steps that encrypt a message; however, the concepts are distinct in cryptography, especially classical cryptography. Codes generally substitute different length strings of characters in the output, while ciphers generally substitute the same number of characters as are input. A code maps one meaning with another. Words and phrases can be coded as letters or numbers. Codes typically have direct meaning from input to key. Codes primarily function to save time. Ciphers are algorithmic. The given input must follow the cipher's process to be solved. Ciphers are commonly used to encrypt written info ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Anonymous Remailer
An anonymous remailer is a server that receives messages with embedded instructions on where to send them next, and that forwards them without revealing where they originally came from. There are cypherpunk anonymous remailers, mixmaster anonymous remailers, and nym servers, among others, which differ in how they work, in the policies they adopt, and in the type of attack on the anonymity of e-mail they can (or are intended to) resist. ''Remailing'' as discussed in this article applies to e-mails intended for particular recipients, not the general public. Anonymity in the latter case is more easily addressed by using any of several methods of anonymous publication. Types of remailer There are several strategies that affect the anonymity of the handled e-mail. In general, different classes of anonymous remailers differ with regard to the choices their designers/operators have made. These choices can be influenced by the legal ramifications of operating specific types of remaile ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Dining Cryptographers Problem
In cryptography, the dining cryptographers problem studies how to perform a secure multi-party computation of the boolean-XOR function. David Chaum first proposed this problem in the early 1980s and used it as an illustrative example to show that it was possible to send anonymous messages with unconditional sender and recipient untraceability. Anonymous communication networks based on this problem are often referred to as DC-nets (where DC stands for "dining cryptographers"). Despite the word ''dining'', the dining cryptographers problem is unrelated to the dining philosophers problem. Description Three cryptographers gather around a table for dinner. The waiter informs them that the meal has been paid for by someone, who could be one of the cryptographers or the National Security Agency (NSA). The cryptographers respect each other's right to make an anonymous payment, but want to find out whether the NSA paid. So they decide to execute a two-stage protocol. In the first stag ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Crypto System
In cryptography, a cryptosystem is a suite of cryptographic algorithms needed to implement a particular security service, such as confidentiality (encryption). Typically, a cryptosystem consists of three algorithms: one for key generation, one for encryption, and one for decryption. The term ''cipher'' (sometimes ''cypher'') is often used to refer to a pair of algorithms, one for encryption and one for decryption. Therefore, the term ''cryptosystem'' is most often used when the key generation algorithm is important. For this reason, the term ''cryptosystem'' is commonly used to refer to public key techniques; however both "cipher" and "cryptosystem" are used for symmetric key techniques. Formal definition Mathematically, a cryptosystem or encryption scheme can be defined as a tuple (\mathcal,\mathcal,\mathcal,\mathcal,\mathcal) with the following properties. # \mathcal is a set called the "plaintext space". Its elements are called plaintexts. # \mathcal is a set called the "c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Authentication
Authentication (from ''authentikos'', "real, genuine", from αὐθέντης ''authentes'', "author") is the act of proving an Logical assertion, assertion, such as the Digital identity, identity of a computer system user. In contrast with identification, the act of indicating a person or thing's identity, authentication is the process of verifying that identity. Authentication is relevant to multiple fields. In art, antiques, and anthropology, a common problem is verifying that a given artifact was produced by a certain person, or in a certain place (i.e. to assert that it is not counterfeit), or in a given period of history (e.g. by determining the age via carbon dating). In computer science, verifying a user's identity is often required to allow access to confidential data or systems. It might involve validating personal identity documents. In art, antiques and anthropology Authentication can be considered to be of three types: The ''first'' type of authentication is accep ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Electronic Voting
Electronic voting is voting that uses electronic means to either aid or handle casting and counting ballots including voting time. Depending on the particular implementation, e-voting may use standalone '' electronic voting machines'' (also called EVM) or computers connected to the Internet (online voting). It may encompass a range of Internet services, from basic transmission of tabulated results to full-function online voting through common connectable household devices. The degree of automation may be limited to marking a paper ballot, or may be a comprehensive system of vote input, vote recording, data encryption and transmission to servers, and consolidation and tabulation of election results. A worthy e-voting system must perform most of these tasks while complying with a set of standards established by regulatory bodies, and must also be capable to deal successfully with strong requirements associated with security, accuracy, speed, privacy, auditability, accessib ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Secure Multiparty Computation
Secure multi-party computation (also known as secure computation, multi-party computation (MPC) or privacy-preserving computation) is a subfield of cryptography with the goal of creating methods for parties to jointly compute a function over their inputs while keeping those inputs private. Unlike traditional cryptographic tasks, where cryptography assures security and integrity of communication or storage and the adversary is outside the system of participants (an eavesdropper on the sender and receiver), the cryptography in this model protects participants' privacy from each other. The foundation for secure multi-party computation started in the late 1970s with the work on mental poker, cryptographic work that simulates game playing/computational tasks over distances without requiring a trusted third party. Traditionally, cryptography was about concealing content, while this new type of computation and protocol is about concealing partial information about data while computing with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Commitment Scheme
A commitment scheme is a cryptographic primitive that allows one to commit to a chosen value (or chosen statement) while keeping it hidden to others, with the ability to reveal the committed value later.Oded Goldreich (2001). Foundations of Cryptography': Volume 1, Basic Tools. Cambridge University Press. . Commitment schemes are designed so that a party cannot change the value or statement after they have committed to it: that is, commitment schemes are ''binding''. Commitment schemes have important applications in a number of cryptographic protocols including secure coin flipping, zero-knowledge proofs, and secure computation. A way to visualize a commitment scheme is to think of a sender as putting a message in a locked box, and giving the box to a receiver. The message in the box is hidden from the receiver, who cannot open the lock themselves. Since the receiver has the box, the message inside cannot be changed—merely revealed if the sender chooses to give them the key ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Alice And Bob
Alice and Bob are fictional characters commonly used as placeholders in discussions about cryptography, cryptographic systems and Cryptographic protocol, protocols, and in other science and engineering literature where there are several participants in a thought experiment. The Alice and Bob characters were created by Ron Rivest, Adi Shamir, and Leonard Adleman in their 1978 paper "A Method for Obtaining Digital Signatures and Public-key Cryptosystems". Subsequently, they have become common archetypes in many scientific and engineering fields, such as quantum cryptography, game theory and physics. As the use of Alice and Bob became more widespread, additional characters were added, sometimes each with a particular meaning. These characters do not have to refer to people; they refer to generic agents which might be different computers or even different programs running on a single computer. Overview Alice and Bob are the names of fictional characters used for convenience and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Tabula Recta
In cryptography, the ''tabula recta'' (from Latin language, Latin ''wikt:tabula#Latin, tabula wikt:rectus#Latin, rēcta'') is a square table of alphabets, each row of which is made by shifting the previous one to the left. The term was invented by the German author and monk Johannes TrithemiusSalomon, Data Privacy, page 63 in 1508, and used in his Trithemius cipher. Trithemius cipher The Trithemius cipher was published by Johannes Trithemius in his book ''Polygraphia (book), Polygraphia'', which is credited with being the first published printed work on cryptology. Trithemius used the ''tabula recta'' to define a polyalphabetic cipher, which was equivalent to Leon Battista Alberti's Alberti cipher disk, cipher disk except that the order of the letters in the target alphabet is not mixed. The ''tabula recta'' is often referred to in discussing pre-computer ciphers, including the Vigenère cipher and Blaise de Vigenère's less well-known autokey cipher. All polyalphabetic ciphe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |