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The Vigenère cipher is a classical cipher that shifts each plaintext character by the value of the key at the same position modulo the key-length.
122 questions
A feistel-network or feistel cipher is a structure that has been used to create a number of different block ciphers (e.g., DES, Blowfish, Twofish, RC6).
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SHA-512 is part of the SHA-2 family of hash functions with a 512-bit output and a 256-bit security level.
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Encoding is the act of transforming information from one form to another. In cryptography, encoding is typically used to refer to an unkeyed process that does not provide any security in itself, but j…
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A man-in-the-middle (MITM) attack is 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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A block cypher encryption algorithm built from applying three iterations of the original DES algorithm.
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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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PKI is short for Public Key Infrastructure. The foundation of a PKI is the certificate authority (CA), which issues digital certificates that authenticate the identity of organizations and individuals…
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Questions about official cryptographic standards and their implementation.
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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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Data privacy refers to (cryptographic) methods to prevent the disclosure of sensitive (identifying) information of persons.
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Quantum cryptography describes the use of quantum mechanical effects to perform cryptographic tasks. This is not to be confused with quantum computing or cryptanalysis techniques such as Shor's algori…
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Cipher Block Chaining MAC (CBC-MAC) is a method of building a message authentication code from a block-cipher.
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A digital signature algorithm based on the discrete logarithm problem, provably secure in the random oracle model.
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Using the same key for more than one purpose, e.g. to encrypt two messages or to encrypt and authenticate a message. Some cryptosystems may be vulnerable to attacks if keys are inappropriately reused.
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RC4 is a fast and simple stream cipher used correctly in SSL and incorrectly in WEP.
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Ring learning with errors (RLWE) is a computational problem which serves as the foundation of new cryptographic algorithms, such as NewHope, designed to protect against cryptanalysis by quantum comput…
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Rijndael is a family of symmetric block-ciphers with block and keys sizes of 128, 160, 192, 224, or 256 bits.
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side channel attack based on the different speed at which certain operations are executed.
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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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Multiple encryption means encrypting a message two or more times using either the same, or a different algorithm.
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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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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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SHA-3, originally known as Keccak, is a cryptographic hash function designed by Guido Bertoni, Joan Daemen, Michaël Peeters, and Gilles Van Assche.
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Linear cryptanalysis is a known plaintext attack and uses a linear approximation to describe the behavior of the block cipher. Given sufficient pairs of plaintext and corresponding ciphertext, bits of…
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Attribute-Based Encryption is a type of public-key encryption in which the key used for encryption is based on selected attributes of the readers. Decryption of the ciphertext is possible only if the …
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HKDF is a key derivation function specified in RFC5869.
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The Merkle–Damgård construction — used in the design of many popular hash algorithms such as MD5, SHA1 and SHA2 — is a method of building collision-resistant cryptographic hash functions from collisio…
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ECC is an approach to public-key cryptography based on the algebraic structure of elliptic curves over finite fields. ECC allows smaller keys compared to non-EC cryptography (based on plain Galois fie…
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Threshold cryptography is the art of chopping a secret into little bits, so that the secret can only be learned by possessing more than a threshold number of those bits.
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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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Steganography is the art and science of writing hidden messages in such a way that no one, apart from the sender and intended recipient, suspects the existence of the message. While cryptography prot…
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bcrypt is an intentionally slow hash algorithm specially designed for passwords.
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NTRU is an encryption algorithm which is based on the shortest vector problem in a lattice.
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produces ciphertext that, by itself, does not reveal information about the original message besides its length
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A birthday attack is a cryptanalytic technique. Birthday attacks can be used to find collisions in a cryptographic hash function. For instance, suppose we have a hash function which, when supplied wit…
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