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 numbers. The PRNG-generated sequence is not truly random, because it is completely determined by an initial value, called the PRNG's seed. Although sequences that are closer to truly random can be generated using hardware random number generators, pseudorandom number generators are important in practice for their speed in number generation and their reproducibility.
The Yarrow algorithm is a family of cryptographic pseudorandom number generators (CSPRNG) devised by John Kelsey, Bruce Schneier, and Niels Ferguson and published in 1999. The Yarrow algorithm is explicitly unpatented, royalty-free, and open source; no license is required to use it. An improved design from Ferguson and Schneier, Fortuna, is described in their book, Practical Cryptography
A cryptographically secure pseudorandom number generator (CSPRNG) or cryptographic pseudorandom number generator (CPRNG) is a pseudorandom number generator (PRNG) with properties that make it suitable for use in cryptography. It is also loosely known as a cryptographic random number generator (CRNG).
Niels T. Ferguson is a Dutch cryptographer and consultant who currently works for Microsoft. He has worked with others, including Bruce Schneier, designing cryptographic algorithms, testing algorithms and protocols, and writing papers and books. Among the designs Ferguson has contributed to is the AES finalist block cipher algorithm Twofish as well as the stream cipher Helix and the Skein hash function.
In Unix-like operating systems, /dev/random and /dev/urandom are special files that serve as cryptographically secure pseudorandom number generators (CSPRNGs). They allow access to a CSPRNG that is seeded with entropy from environmental noise, collected from device drivers and other sources. /dev/random typically blocks if there was less entropy available than requested; more recently it usually blocks at startup until sufficient entropy has been gathered, then unblocks permanently. The /dev/urandom device typically was never a blocking device, even if the pseudorandom number generator seed was not fully initialized with entropy since boot. Not all operating systems implement the same methods for /dev/random and /dev/urandom.
In cryptography, nothing-up-my-sleeve numbers are any numbers which, by their construction, are above suspicion of hidden properties. They are used in creating cryptographic functions such as hashes and ciphers. These algorithms often need randomized constants for mixing or initialization purposes. The cryptographer may wish to pick these values in a way that demonstrates the constants were not selected for a nefarious purpose, for example, to create a backdoor to the algorithm. These fears can be allayed by using numbers created in a way that leaves little room for adjustment. An example would be the use of initial digits from the number π as the constants. Using digits of π millions of places after the decimal point would not be considered trustworthy because the algorithm designer might have selected that starting point because it created a secret weakness the designer could later exploit—though even with natural-seeming selections, enough entropy exists in the possible choices that the utility of these numbers has been questioned.
The security of cryptographic systems depends on some secret data that is known to authorized persons but unknown and unpredictable to others. To achieve this unpredictability, some randomization is typically employed. Modern cryptographic protocols often require frequent generation of random quantities. Cryptographic attacks that subvert or exploit weaknesses in this process are known as random number generator attacks.
A random password generator is a software program or hardware device that takes input from a random or pseudo-random number generator and automatically generates a password. Random passwords can be generated manually, using simple sources of randomness such as dice or coins, or they can be generated using a computer.
Fortuna is a cryptographically secure pseudorandom number generator (CS-PRNG) devised by Bruce Schneier and Niels Ferguson and published in 2003. It is named after Fortuna, the Roman goddess of chance. FreeBSD uses Fortuna for /dev/random and /dev/urandom is symbolically linked to it since FreeBSD 11. Apple OSes have switched to Fortuna since 2020 Q1.
Random number generation is a process by which, often by means of a random number generator (RNG), a sequence of numbers or symbols that cannot be reasonably predicted better than by random chance is generated. This means that the particular outcome sequence will contain some patterns detectable in hindsight but impossible to foresee. True random number generators can be hardware random-number generators (HRNGs), wherein each generation is a function of the current value of a physical environment's attribute that is constantly changing in a manner that is practically impossible to model. This would be in contrast to so-called "random number generations" done by pseudorandom number generators (PRNGs), which generate numbers that only look random but are in fact pre-determined—these generations can be reproduced simply by knowing the state of the PRNG.
The Microsoft Windows platform specific Cryptographic Application Programming Interface is an application programming interface included with Microsoft Windows operating systems that provides services to enable developers to secure Windows-based applications using cryptography. It is a set of dynamically linked libraries that provides an abstraction layer which isolates programmers from the code used to encrypt the data. The Crypto API was first introduced in Windows NT 4.0 and enhanced in subsequent versions.
The Native API is a lightweight application programming interface (API) used by Windows NT and user mode applications. This API is used in the early stages of Windows NT startup process, when other components and APIs are still unavailable. Therefore, a few Windows components, such as the Client/Server Runtime Subsystem (CSRSS), are implemented using the Native API. The Native API is also used by subroutines such as those in kernel32.dll that implement the Windows API, the API based on which most of the Windows components are created.
The Microsoft Windows operating system supports a form of shared libraries known as "dynamic-link libraries", which are code libraries that can be used by multiple processes while only one copy is loaded into memory. This article provides an overview of the core libraries that are included with every modern Windows installation, on top of which most Windows applications are built.
In computing, entropy is the randomness collected by an operating system or application for use in cryptography or other uses that require random data. This randomness is often collected from hardware sources, either pre-existing ones such as mouse movements or specially provided randomness generators. A lack of entropy can have a negative impact on performance and security.
Dual_EC_DRBG is an algorithm that was presented as a cryptographically secure pseudorandom number generator (CSPRNG) using methods in elliptic curve cryptography. Despite wide public criticism, including the public identification of the possibility that the National Security Agency put a backdoor into a recommended implementation, it was for seven years one of four CSPRNGs standardized in NIST SP 800-90A as originally published circa June 2006, until it was withdrawn in 2014.
There are various implementations of the Advanced Encryption Standard, also known as Rijndael.
RDRAND 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. Intel introduced the feature around 2012, and AMD added support for the instruction in June 2015.
Dell BSAFE, formerly known as RSA BSAFE, is a FIPS 140-2 validated cryptography library, available in both C and Java. BSAFE was initially created by RSA Security, which was purchased by EMC and then, in turn, by Dell. When Dell sold the RSA business to Symphony Technology Group in 2020, Dell elected to retain the BSAFE product line. BSAFE was one of the most common encryption toolkits before the RSA patent expired in September 2000. It also contained implementations of the RCx ciphers, with the most common one being RC4. From 2004 to 2013 the default random number generator in the library was a NIST-approved RNG standard, widely known to be insecure from at least 2006, containing a kleptographic backdoor from the American National Security Agency (NSA), as part of its secret Bullrun program. In 2013 Reuters revealed that RSA had received a payment of $10 million to set the compromised algorithm as the default option. The RNG standard was subsequently withdrawn in 2014, and the RNG removed from BSAFE beginning in 2015.
Entropy-supplying system calls are system calls in Unix-like operating system kernels through which processes can obtain entropic or random data. The first of these was getentropy, introduced to the OpenBSD operating system in release 5.6, as a refactoring of the sysctl(3) KERN_ARND approach used since 1997. Linux offers a very similar system call, getrandom, which was based on getentropy. It was first available in Linux 3.17, released in October 2014. In July 2015, Solaris introduced slightly modified versions of getentropy and getrandom. In August 2015, FreeBSD introduced the read_random system call for obtaining random data from the kernel.
A counter-based random number generation is a kind of pseudorandom number generator that uses only an integer counter as its internal state. They are generally used for generating pseudorandom numbers for large parallel computations.
