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A cryptographic hash function (CHF) is a hash algorithm (a map of an arbitrary binary string to a binary string with a fixed size of bits) that has special properties desirable for a cryptographic application: [ 1 ] the probability of a particular n {\displaystyle n} -bit output result (hash value) for a random input string ("message") is 2 − ...
One-time pad. A format of one-time pad used by the U.S. National Security Agency, code named DIANA. The table on the right is an aid for converting between plaintext and ciphertext using the characters at left as the key. In cryptography, the one-time pad (OTP) is an encryption technique that cannot be cracked, but requires the use of a single ...
Caesar cipher. The action of a Caesar cipher is to replace each plaintext letter with a different one a fixed number of places down the alphabet. The cipher illustrated here uses a left shift of 3, so that (for example) each occurrence of E in the plaintext becomes B in the ciphertext. In cryptography, a Caesar cipher, also known as Caesar's ...
A hash function is any function that can be used to map data of arbitrary size to fixed-size values, though there are some hash functions that support variable-length output. [ 1 ] The values returned by a hash function are called hash values, hash codes, hash digests, digests, or simply hashes. [ 2 ] The values are usually used to index a ...
Padding (cryptography) In cryptography, padding is any of a number of distinct practices which all include adding data to the beginning, middle, or end of a message prior to encryption. In classical cryptography, padding may include adding nonsense phrases to a message to obscure the fact that many messages end in predictable ways, e.g ...
Space. Θ (n) [ 1 ] O (n) A small phone book as a hash table. In computing, a hash table is a data structure that implements an associative array, also called a dictionary or simply map; an associative array is an abstract data type that maps keys to values. [ 2 ] A hash table uses a hash function to compute an index, also called a hash code ...
In cryptography, a salt is random data fed as an additional input to a one-way function that hashes data, a password or passphrase. [1] Salting helps defend against attacks that use precomputed tables (e.g. rainbow tables), by vastly growing the size of table needed for a successful attack. [2][3][4] It also helps protect passwords that occur ...
Data structure alignment is the way data is arranged and accessed in computer memory. It consists of three separate but related issues: data alignment, data structure padding, and packing. The CPU in modern computer hardware performs reads and writes to memory most efficiently when the data is naturally aligned, which generally means that the ...