A tag is a keyword or label that categorizes your question with other, similar questions. Using the right tags makes it easier for others to find and answer your question.

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The National Institute of Standards and Technology (NIST) is a U.S. federal agency that works with industry to develop and apply technology, measurements, and standards.
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an attack model for cryptanalysis in which the cryptanalyst gathers information, at least in part, by choosing a ciphertext and obtaining its decryption under an un…
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a structure that has been used to create a number of different block ciphers (e.g., DES, Blowfish, Twofish, RC6).
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A digital signature scheme based on the discrete logarithm problem, published by Taher ElGamal in 1984. Not to be confused with the ElGamal encryption system.
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an encryption algorithm that can be used as a replacement for the DES or IDEA algorithms. Blowfish was designed in 1993 by Bruce Schneier as an alternative to existing encryption algorithm…
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a password that is valid for only one session or transaction.
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Multiple encryption means encrypting a message two or more times using either the same, or a different algorithm.
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based on a mathematical problem that is moderate hard to solve but easy to verify.
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A public-key cryptosystem invented by Pascal Paillier in 1999.
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an active attack where the attacker is able to interpose himself between the sender and receiver. The attacker may monitor and/or modify some or all of the messag…
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Format-preserving encryption (FPE) refers to encrypting in such a way that the output has the same length as the input, or otherwise has the same format or structure as the input.
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for questions about cryptographic algorithms which were invented (and used) before the computer age.
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a classical cipher that shifts each plaintext character by the value of the key at the same position modulo the key-length.
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a digital peer-to-peer currency with no central authority. It was created in 2009 by Satoshi Nakamoto. Transactions are managed entirely by the network.
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Anonymity describes the state of being unknown or unacknowledged.
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a protocol where one party commits themselves to a secret value without revealing it. At a later point, the value can be revealed.
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In identity-based encryption (IBE) the public key of a user $A$ is some identity string $ID_A$, e.g., an email address. To encrypt a message for this user there is no need to retrieve an authentic cop…
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Performance defines the abilities of a cipher in terms of processing throughput on various platforms, including its memory requirements.
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a function that cannot be distinguished (with practical effort) from a permutation selected at random with uniform probability from the family of all permutations …
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an arbitrary number or string used only once within the context of a specific cryptographic scheme. Nonces are used e.g. in authentication protocols to prevent replay attacks, as well as …
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the reduction in size of data without losing information.
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an algorithm for producing digital signatures. The algorithm is based on Edwards curves introduced by Bernstein et al. (2007) and named after mathematician Harold M. Edwards.
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a key derivation function specified in RFC5869.
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In a blind signature scheme, the signer does not know what he is signing. This is an important building block of anonymous voting or digital cash schemes, because it allows an authority to control the…
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Questions on the meaning, history, and usage of symbols and notation in cryptography. Please remember to mention where (book, paper, webpage, etc.) you encountered any notation you are asking about.
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Oblivious transfer refers to a cryptographic protocol in which a sender possesses a set of data and a receiver queries the sender for a particular member of that set in such a way that the sender does…
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an optimized brute-force attack that significantly reduces the number of keys the attacker needs to try by utilizing a time-space trade-off. Work is done from the begi…
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a dynamic, object-oriented, prototype-based, weakly typed language commonly used for scripting in web browsers. Despite the name, it is unrelated to the Java programming language and sha…
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produces ciphertext that, by itself, does not reveal information about the original message besides its length
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Difficulty of finding another input string that hashes to the same value as a given string
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A backdoor in a cryptosystem or algorithm allows someone to obtain access to the decrypted data, without the need for the key/password that was used to encrypt the data.
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a historic polygraphic substitution cipher invented by Lester S. Hill in 1929.
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History of cryptography and cryptanalysis. Questions that wish to ask about the history of cryptography should use this tag; if you're asking about historical ciphers you may also wish to use the clas…
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Disk encryption protects information by encrypting every byte that is written to a HD or virtual disk volume.
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a sequence of bytes or bits, having a fixed length (the block-size).
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The term "pen and paper" can practically be interpreted as "using no tools like electronic devices", since it targets cryptographic functions, schemes, and procedures which can be handled by humans wh…