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Cryptography that will remain secure should large-scale quantum computing become feasible. Based on hard problems with no known polynomial-time quantum algorithm (e.g., Shor's algorithm).
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In cryptography, a pseudo-random generator (PRG) is a deterministic procedure that maps a random seed to a longer pseudo-random string such that no statistical test can distinguish between the output …
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(or Data Encryption Standard), a (symmetric) block cipher using a 64 bit block size, with keys of size 56 bit, the standard US block cipher from 1976 to 2001.
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a system of arithmetic for integers, where numbers "wrap around" upon reaching a certain value… the modulus.
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A cipher which uses a different encryption key every time, as long as the message. The key is XOR'ed with the message to render the cipher text which can then be XOR'ed with the same key to get the p…
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Unique data used by block cipher modes of operation to randomize the output in order to achieve semantic security. Also for other similar constructs in other iterative algorithms.
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a family of deterministic functions indexed by a parameter, such that a randomly selected instance is computationally indistinguishable from a uniformly random functi…
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a measure of how predictable the outcome of a random process is, or how much uncertainty one has in one's state of knowledge about an unknown piece of information, defined in terms of the p…
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ways of applying a block cipher to multi-block messages and enabling repeated use without changing the key.
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Multi-party computation (MPC) allows a set of parties, each with a private input, to securely and jointly perform any computation over their inputs.
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an integer greater than 1 with no divisors other than itself and 1. Primes and prime products play an important role in public key cryptography.
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attempting to find a secret value by trying all possible values until the correct one is found.
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an open source implementation of the SSL and TLS protocols. Questions about how to use the OpenSSL tools and libraries are usually better asked at Stack Overflow or Super User.
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a public key encryption scheme with security based on the discrete logarithm problem.
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a hash function that is two generations old, no longer considered secure for all uses and should only be used for backward compatibility.
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Padding has two primary uses in cryptography, ensuring messages are the proper length necessary for certain ciphers (e.g., block ciphers) or to provide assurances not built into the core cipher (e.g.,…
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A cryptographic attack tries to theoretically and/or practically attack the security properties of a cipher and/or algorithm.
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a mathematical construct based on a set of axioms which are held to be true. A number of interesting and useful properties arise from finite fields that makes them particularly suita…
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The Galois Counter Mode, an authenticated encryption mode of operation for a block cipher.
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the size measured in bits of the key used in a cryptographic algorithm.
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The attacker can specify his own plain text and encrypt or sign it.
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the study and use of lattice problems applied to cryptography.
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a hash function that is no longer considered secure from a cryptographic point of view. Therefore, it should only be used for backward compatibility.
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one of the basic operations on bits and bit-sequences. It is a building block of many cryptographic primitives (and some higher-level algorithms, like modes of operations).
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Questions about the meaning and proper use of specific technical terms or notation within cryptography.
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A certificate consists of a public key and information about the owner (e. g. the name of a person or server).
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The Password-Based Key Derivation Function 2 (PBKDF2) is a method of securely deriving encryption keys from a passphrase entered by a user. It features an iteration count that can be deliberately adju…
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Pairing-based cryptography uses bilinear maps to create a gap group that allows efficient constructions of certain primitives.
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an encryption mode, that builds a random-access stream-cipher from a block-cipher.
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Ciphers invented before the era of computers and modern cryptographic theory. Classical ciphers typically operate on letters instead of bits and are usually designed to be implemented by hand or using…
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The OpenPGP encrypted data format (RFC 4880), and its implementations PGP and GnuPG.
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easy to compute but hard to invert (i.e. find preimages for). The existence of one-way functions implies the possibility of many useful cryptographic schemes. No one-way functions …
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an abstract algebraic concept based on a set and a group law (a binary function which closes the set).
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(or substitution boxes), components in many block ciphers used to substitute parts of the data in a non-linear way. While often fixed by the algorithm (like in DES and AES), sometimes they are key-dep…
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Complexity describes - in simple words - how hard (complex) it is to reach a specific goal; and under which conditions. In cryptography, this mostly ends up in using the complexity theory to analyze t…