|
Urandom
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 (a value that provides randomness) from environmental noise, collected from device drivers and other sources. Users can obtain random numbers from the CSPRNG simply by reading the file. Not all operating systems implement the same methods for and . In older operating systems, typically blocked if there was less entropy available than requested; more recently (see below for the differences between operating systems) it usually blocks at startup until sufficient entropy has been gathered, then unblocks permanently. The device typically was never a blocking device, even if the pseudorandom number generator seed was not fully initialized with entropy since boot. This special file originated in Linux in 1994. It was quickly adopted by other Unix-like operating systems. Linux The Linux kernel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Entropy (computing)
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 (variance in fan noise or HDD), 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. Linux kernel The Linux kernel generates entropy from Keyboard (computing), keyboard timings, Mouse (computing), mouse movements, and integrated drive electronics (IDE) timings and makes the random character data available to other operating system processes through the special files /dev/random and /dev/urandom. This capability was introduced in Linux version 1.3.30. There are some Linux kernel patches allowing one to use more entropy sources. The audio_entropyd project, which is included in some operating systems such as Fedora (operating system), Fedora, allows audio data ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cryptographically Secure Pseudorandom Number Generator
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 referred to as a cryptographic random number generator (CRNG). Background Most cryptographic applications require random numbers, for example: * key generation * initialization vectors * nonces * salts in certain signature schemes, including ECDSA and RSASSA-PSS * token generation The "quality" of the randomness required for these applications varies. For example, creating a nonce in some protocols needs only uniqueness. On the other hand, the generation of a master key requires a higher quality, such as more entropy. And in the case of one-time pads, the information-theoretic guarantee of perfect secrecy only holds if the key material comes from a true random source with high entropy, and thus just any kind of pseudorandom number gener ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ChaCha20
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. ChaCha is a modification of Salsa20 published in 2008. It uses a new round function that increases diffusion and increases performance on some architectures. Both ciphers are built on a pseudorandom function based on add–rotate–XOR (ARX) operations — 32-bit addition, bitwise addition (XOR) and rotation operations. The core function maps a 256-bit key, a 64-bit nonce, and a 64-bit counter to a 512-bit block of the key stream (a Salsa version with a 128-bit key also exists). This gives Salsa20 and ChaCha the unusual advantage that the user can efficiently seek to any position in the key stream in constant time. Salsa20 offers speeds of around 4–14 cycles per byte in software on modern x86 processors, and reasonable hardware perfor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Special File
In Unix-like operating systems, a device file, device node, or special file is an interface to a device driver that appears in a file system as if it were an ordinary file. There are also special files in DOS, OS/2, and Windows. These special files allow an application program to interact with a device by using its device driver via standard input/output system calls. Using standard system calls simplifies many programming tasks, and leads to consistent user-space I/O mechanisms regardless of device features and functions. Overview Device files usually provide simple interfaces to standard devices (such as printers and serial ports), but can also be used to access specific unique resources on those devices, such as disk partitions. Additionally, device files are useful for accessing system resources that have no connection with any actual device, such as data sinks and random number generators. There are two general kinds of device files in Unix-like operating systems, kno ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Entropy Pool
In computing, a hardware random number generator (HRNG), true random number generator (TRNG), non-deterministic random bit generator (NRBG), or physical random number generator is a device that generates random numbers from a physical process capable of producing entropy, unlike a pseudorandom number generator (PRNG) that utilizes a deterministic algorithm and non-physical nondeterministic random bit generators that do not include hardware dedicated to generation of entropy. Many natural phenomena generate low-level, statistically random "noise" signals, including thermal and shot noise, jitter and metastability of electronic circuits, Brownian motion, and atmospheric noise. Researchers also used the photoelectric effect, involving a beam splitter, other quantum phenomena, and even the nuclear decay (due to practical considerations the latter, as well as the atmospheric noise, is not viable except for fairly restricted applications or online distribution services). While "cl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Everything2
Everything2 (styled Everything2 or E2 for short) is a collaborative online community consisting of a database of interlinked user-submitted written material. E2 is moderated for quality, but has no formal policy on subject matter. Writing on E2 covers a wide range of topics and genres, including encyclopedic articles, diary entries (known as "daylogs"), poetry, humor, and fiction. History The predecessor of E2 was a similar database called Everything (later labeled "Everything1" or "E1") which was started around March 1998 by Nathan Oostendorp and was initially closely aligned with and promoted by the technology-related news website Slashdot (by virtue of various key principals having attended the Holland Christian High School), even sharing (at the time) some administrators. The Everything2 software offered vastly more features, and the Everything1 data was twice incorporated into E2: once on November 13, 1999, and again in January 2000. The Everything2 server used to be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 is to convert information into cipher or code. In common parlance, "cipher" is synonymous with "code (cryptography), code", as they are both a set of steps that encrypt a message; however, the concepts are distinct in cryptography, especially classical cryptography. Codes generally substitute different length strings of characters in the output, while ciphers generally substitute the same number of characters as are input. A code maps one meaning with another. Words and phrases can be coded as letters or numbers. Codes typically have direct meaning from input to key. Codes primarily function to save time. Ciphers are algorithmic. The given input must follow the cipher's process to be solved. Ciphers are commonly used to encrypt written info ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Export Of Cryptography
The export of cryptography is the transfer from one country to another of devices and technology related to cryptography. In the early days of the Cold War, the United States and its allies developed an elaborate series of export control regulations designed to prevent a wide range of Western technology from falling into the hands of others, particularly the Eastern bloc. All export of technology classed as 'critical' required a license. CoCom was organized to coordinate Western export controls. Many countries, notably those participating in the Wassenaar Arrangement The Wassenaar Arrangement on Export Controls for Conventional Arms and Dual-Use Goods and Technologies, also known simply as the Wassenaar Arrangement, is a multilateral export control regime governing the international transfer of conventional ..., introduced restrictions. The Wassenaar restrictions were largely loosened in the late 2010s. See also * Crypto wars * Export of cryptography from the United Stat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hexdump Of Dev Urandom
In computing, a hex dump is a textual hexadecimal view (on screen or paper) of computer data, from memory or from a computer file or storage device. Use of a hex dump of data is usually done in the context of either debugging, reverse engineering or digital forensics. Interactive editors that provide a similar view but also manipulating the data in question are called hex editors. In a hex dump, each byte (8 bits) is represented as a two-digit hexadecimal number. Hex dumps are commonly organized into rows of 8 or 16 bytes, sometimes separated by whitespaces. Some hex dumps have the hexadecimal memory address at the beginning. On systems where the conventional representation of data is octal, the equivalent is an ''octal dump''. Some common names for this program function are hexdump, hd, od, xxd and simply dump or even D. Samples The following sample shows output from unix program hexdump, other systems have programs which generate similar output. 0123456789ABCDEF /* **** ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Entropy Pool
In computing, a hardware random number generator (HRNG), true random number generator (TRNG), non-deterministic random bit generator (NRBG), or physical random number generator is a device that generates random numbers from a physical process capable of producing entropy, unlike a pseudorandom number generator (PRNG) that utilizes a deterministic algorithm and non-physical nondeterministic random bit generators that do not include hardware dedicated to generation of entropy. Many natural phenomena generate low-level, statistically random "noise" signals, including thermal and shot noise, jitter and metastability of electronic circuits, Brownian motion, and atmospheric noise. Researchers also used the photoelectric effect, involving a beam splitter, other quantum phenomena, and even the nuclear decay (due to practical considerations the latter, as well as the atmospheric noise, is not viable except for fairly restricted applications or online distribution services). While "cl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
