Random number generators Random number generation is a process by which, often by means of a random number generator (RNG), a sequence of numbers or symbols is generated that cannot be reasonably predicted better than by random chance. This means that the particular ou ...

are important in many kinds of technical applications, including

physics Physics is the scientific study of matter, its Elementary particle, fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge whi ...

engineering Engineering is the practice of using natural science, mathematics, and the engineering design process to Problem solving#Engineering, solve problems within technology, increase efficiency and productivity, and improve Systems engineering, s ...

mathematical Mathematics is a field of study that discovers and organizes methods, Mathematical theory, theories and theorems that are developed and Mathematical proof, proved for the needs of empirical sciences and mathematics itself. There are many ar ...

computer studies (e.g.,

Monte Carlo Monte Carlo ( ; ; or colloquially ; , ; ) is an official administrative area of Monaco, specifically the Ward (country subdivision), ward of Monte Carlo/Spélugues, where the Monte Carlo Casino is located. Informally, the name also refers to ...

simulations),

cryptography Cryptography, or cryptology (from "hidden, secret"; and ''graphein'', "to write", or ''-logy, -logia'', "study", respectively), is the practice and study of techniques for secure communication in the presence of Adversary (cryptography), ...

and

gambling Gambling (also known as betting or gaming) is the wagering of something of Value (economics), value ("the stakes") on a Event (probability theory), random event with the intent of winning something else of value, where instances of strategy (ga ...

(on

game server A game server (also sometimes referred to as a host) is a server which is the authoritative source of events in a multiplayer video game. The server transmits enough data about its internal state to allow its connected clients to maintain thei ...

s). This list includes many common types, regardless of quality or applicability to a given use case.

Pseudorandom number generators (PRNGs)

The following algorithms are

pseudorandom number generator A pseudorandom number generator (PRNG), also known as a deterministic random bit generator (DRBG), is an algorithm for generating a sequence of numbers whose properties approximate the properties of sequences of random number generation, random n ...

Cryptographic algorithms

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 i ...

algorithms and

cryptographic hash 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 n bits) that has special properties desirable for a cryptographic application: * the probability of a particu ...

es can be used as very high-quality pseudorandom number generators. However, generally they are considerably slower (typically by a factor 2–10) than fast, non-cryptographic random number generators. These include: *

Stream cipher stream cipher is a symmetric key cipher where plaintext digits are combined with a pseudorandom cipher digit stream ( keystream). In a stream cipher, each plaintext digit is encrypted one at a time with the corresponding digit of the keystrea ...

s. Popular choices are

Salsa20 Salsa20 and the closely related ChaCha are stream ciphers developed by Daniel J. Bernstein. Salsa20, the original cipher, was designed in 2005, then later submitted to the eSTREAM European Union cryptographic validation process by Bernstein. Ch ...

ChaCha Cha-Cha, Cha Cha, ChaCha or Chacha may refer to: Music *Cha-cha-cha (dance), a dance of Cuban origin *Cha-cha-cha (music), a genre of Cuban music *Cha Cha (album), ''Cha Cha'' (album), a 1978 album by Herman Brood & His Wild Romance *Cha Cha (sou ...

(often with the number of rounds reduced to 8 for speed),

ISAAC Isaac ( ; ; ; ; ; ) is one of the three patriarchs (Bible), patriarchs of the Israelites and an important figure in the Abrahamic religions, including Judaism, Christianity, Islam, and the Baháʼí Faith. Isaac first appears in the Torah, in wh ...

, HC-128 and

RC4 In cryptography, RC4 (Rivest Cipher 4, also known as ARC4 or ARCFOUR, meaning Alleged RC4, see below) is a stream cipher. While it is remarkable for its simplicity and speed in software, multiple vulnerabilities have been discovered in RC4, ren ...

. *

Block cipher In cryptography, a block cipher is a deterministic algorithm that operates on fixed-length groups of bits, called ''blocks''. Block ciphers are the elementary building blocks of many cryptographic protocols. They are ubiquitous in the storage a ...

s in

counter mode In cryptography, a block cipher mode of operation is an algorithm that uses a block cipher to provide information security such as confidentiality or authenticity. A block cipher by itself is only suitable for the secure cryptographic transform ...

. Common choices are AES (which is very fast on systems supporting it in hardware),

TwoFish In cryptography, Twofish is a symmetric key block cipher with a block size of 128 bits and key sizes up to 256 bits. It was one of the five finalists of the Advanced Encryption Standard contest, but it was not selected for standardization. Two ...

, Serpent and

Camellia ''Camellia'' (pronounced or ) is a genus of flowering plants in the family Theaceae. They are found in tropical and subtropical areas in East Asia, eastern and South Asia, southern Asia, from the Himalayas east to Japan and Indonesia. There are ...

. *

Cryptographic hash function A cryptographic hash function (CHF) is a hash algorithm (a map (mathematics), map of an arbitrary binary string to a binary string with a fixed size of n bits) that has special properties desirable for a cryptography, cryptographic application: ...

s A few cryptographically secure pseudorandom number generators do not rely on cipher algorithms but try to link mathematically the difficulty of distinguishing their output from a `true' random stream to a computationally difficult problem. These approaches are theoretically important but are too slow to be practical in most applications. They include: * Blum–Micali algorithm (1984) *

Blum Blum Shub Blum Blum Shub (B.B.S.) is a pseudorandom number generator proposed in 1986 by Lenore Blum, Manuel Blum and Michael Shub that is derived from Michael O. Rabin's one-way function. __TOC__ Blum Blum Shub takes the form :x_ = x_n^2 \bmod M, where ...

(1986) *

Naor–Reingold pseudorandom function In 1997, Moni Naor and Omer Reingold described efficient constructions for various cryptographic primitives in private key as well as public-key cryptography. Their result is the construction of an efficient pseudorandom function. Let ''p'' and '' ...

(1997)

Random number generators that use external entropy

These approaches combine a pseudo-random number generator (often in the form of a block or stream cipher) with an external source of randomness (e.g., mouse movements, delay between keyboard presses etc.). *

/dev/random 

In Unix-like operating systems,  and  are special files that provide random numbers from a cryptographically secure pseudorandom number generator (CSPRNG). The CSPRNG is seeded with Entropy_(computing), entropy (a value that provides randomness) f ...

–

Unix-like A Unix-like (sometimes referred to as UN*X, *nix or *NIX) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Uni ...

systems *

CryptGenRandom CryptGenRandom is a deprecated cryptographically secure pseudorandom number generator function that is included in Microsoft CryptoAPI. In Win32 programs, Microsoft recommends its use anywhere random number generation is needed. A 2007 paper from H ...

–

Microsoft Windows Windows is a Product lining, product line of Proprietary software, proprietary graphical user interface, graphical operating systems developed and marketed by Microsoft. It is grouped into families and subfamilies that cater to particular sec ...

Fortuna Fortuna (, equivalent to the Greek mythology, Greek goddess Tyche) is the goddess of fortune and the personification of luck in Religion in ancient Rome, Roman religion who, largely thanks to the Late Antique author Boethius, remained popular thr ...

RDRAND RDRAND (for "read random") is an instruction for returning random numbers from an Intel on-chip hardware random number generator which has been seeded by an on-chip entropy source. It is also known as Intel Secure Key Technology, codenamed Bull M ...

instructions (called ''Intel Secure Key'' by

Intel Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California, and Delaware General Corporation Law, incorporated in Delaware. Intel designs, manufactures, and sells computer compo ...

), available in Intel x86 CPUs since 2012. They use the AES generator built into the CPU, reseeding it periodically. *''True Random Number Generator using Corona Discharge.''True Random Number Generator using Corona Discharge: Indian Patent Office. Patent Application Number: 201821026766 *

Yarrow ''Achillea millefolium'', commonly known as yarrow () or common yarrow, is a flowering plant in the family Asteraceae. Growing to tall, it is characterized by small whitish flowers, a tall stem of fernlike leaves, and a pungent odor. The plan ...

* RANDOM.org

References

External links

SP800-90 series on Random Number Generation

NIST The National Institute of Standards and Technology (NIST) is an agency of the United States Department of Commerce whose mission is to promote American innovation and industrial competitiveness. NIST's activities are organized into physical s ...

Random Number Generation in the GNU Scientific Library Reference Manual
* ttps://lomont.org/papers/2008/Lomont_PRNG_2008.pdf Chris Lomont's overview of PRNGs, including a good implementation of the WELL512 algorithmbr>Source code to read data from a TrueRNG V2 hardware TRNG
{{DEFAULTSORT:Random number generators Computing-related lists Mathematics-related lists * *

Pseudorandom number generators (PRNGs)

Cryptographic algorithms

Random number generators that use external entropy

See also

References

External links