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MD2 (cryptography)
The MD2 Message-Digest Algorithm is a cryptographic hash function developed by Ronald Rivest in 1989. The algorithm is optimized for 8-bit computers. MD2 is specified in IETF RFC 1319. The "MD" in MD2 stands for "Message Digest". Even though MD2 is not yet fully compromised, the IETF retired MD2 to "historic" status in 2011, citing "signs of weakness". It is deprecated in favor of SHA-256 and other strong hashing algorithms. Nevertheless, , it remained in use in public key infrastructures as part of certificates generated with MD2 and RSA. Description The 128-bit hash value of any message is formed by padding it to a multiple of the block length (128 bits or 16 bytes) and adding a 16-byte checksum to it. For the actual calculation, a 48-byte auxiliary block and a 256-byte S-table are used. The constants were generated by shuffling the integers 0 through 255 using a variant of Durstenfeld's algorithm with a pseudorandom number generator based on decimal digits of (pi) (s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ronald Rivest
Ronald Linn Rivest (; born May 6, 1947) is an American cryptographer and computer scientist whose work has spanned the fields of algorithms and combinatorics, cryptography, machine learning, and election integrity. He is an Institute Professor at the Massachusetts Institute of Technology (MIT), and a member of MIT's Department of Electrical Engineering and Computer Science and its Computer Science and Artificial Intelligence Laboratory. Along with Adi Shamir and Len Adleman, Rivest is one of the inventors of the RSA algorithm. He is also the inventor of the symmetric key encryption algorithms RC2, RC4, and RC5, and co-inventor of RC6. (''RC'' stands for "Rivest Cipher".) He also devised the MD2, MD4, MD5 and MD6 cryptographic hash functions. Education Rivest earned a bachelor's degree in mathematics from Yale University in 1969, and a Ph.D. degree in computer science from Stanford University in 1974 for research supervised by Robert W. Floyd. Career At MIT, Riv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ASCII
ASCII ( ), an acronym for American Standard Code for Information Interchange, is a character encoding standard for representing a particular set of 95 (English language focused) printable character, printable and 33 control character, control characters a total of 128 code points. The set of available punctuation had significant impact on the syntax of computer languages and text markup. ASCII hugely influenced the design of character sets used by modern computers; for example, the first 128 code points of Unicode are the same as ASCII. ASCII encodes each code-point as a value from 0 to 127 storable as a seven-bit integer. Ninety-five code-points are printable, including digits ''0'' to ''9'', lowercase letters ''a'' to ''z'', uppercase letters ''A'' to ''Z'', and commonly used punctuation symbols. For example, the letter is represented as 105 (decimal). Also, ASCII specifies 33 non-printing control codes which originated with ; most of which are now obsolete. The control cha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SHA-1
In cryptography, SHA-1 (Secure Hash Algorithm 1) is a hash function which takes an input and produces a 160-bit (20-byte) hash value known as a message digest – typically rendered as 40 hexadecimal digits. It was designed by the United States National Security Agency, and is a U.S. Federal Information Processing Standard. The algorithm has been cryptographically broken but is still widely used. Since 2005, SHA-1 has not been considered secure against well-funded opponents; as of 2010 many organizations have recommended its replacement. NIST formally deprecated use of SHA-1 in 2011 and disallowed its use for digital signatures in 2013, and declared that it should be phased out by 2030. , chosen-prefix attacks against SHA-1 are practical. As such, it is recommended to remove SHA-1 from products as soon as possible and instead use SHA-2 or SHA-3. Replacing SHA-1 is urgent where it is used for digital signatures. All major web browser vendors ceased acceptance of SHA-1 SSL certifi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Comparison Of Cryptographic Hash Functions
The following tables compare general and technical information for a number of cryptographic hash functions. See the individual functions' articles for further information. This article is not all-inclusive or necessarily up-to-date. An overview of hash function security/cryptanalysis can be found at hash function security summary. General information Basic general information about the cryptographic hash functions: year, designer, references, etc. Parameters Notes Compression function The following tables compare technical information for compression functions of cryptographic hash functions. The information comes from the specifications, please refer to them for more details. Notes See also * List of hash functions * Hash function security summary * Word (computer architecture) References External links ECRYPT Benchmarking of Cryptographic Hashes– measurements of hash function speed on various platforms The ECRYPT Hash Function Website– A wiki for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hash Function Security Summary
This article summarizes publicly known attacks against cryptographic hash functions. Note that not all entries may be up to date. For a summary of other hash function parameters, see comparison of cryptographic hash functions. Table color key Common hash functions Collision resistance Chosen prefix collision attack Preimage resistance Length extension *Vulnerable: MD5, SHA1, SHA256, SHA512 *Not vulnerable: SHA384, SHA-3, BLAKE2 Less-common hash functions Collision resistance Preimage resistance Attacks on hashed passwords Hashes described here are designed for fast computation and have roughly similar speeds. Because most users typically choose short passwords formed in predictable ways, passwords can often be recovered from their hashed value if a fast hash is used. Searches on the order of 100 billion tests per second are possible with high-end graphics processors. Special hashes called key derivation functions have been created to slow brute for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Network Security Services
Network Security Services (NSS) is a collection of cryptographic computer libraries designed to support cross-platform development of security-enabled client and server applications with optional support for hardware TLS/SSL acceleration on the server side and hardware smart cards on the client side. NSS provides a complete open-source implementation of cryptographic libraries supporting Transport Layer Security (TLS) / Secure Sockets Layer (SSL) and S/MIME. NSS releases prior to version 3.14 are tri-licensed under the Mozilla Public License 1.1, the GNU General Public License, and the GNU Lesser General Public License. Since release 3.14, NSS releases are licensed under GPL-compatible Mozilla Public License 2.0. History NSS originated from the libraries developed when Netscape invented the SSL security protocol. FIPS 140 validation and NISCC testing The NSS software crypto module has been validated five times (in 1997, 1999, 2002, 2007, and 2010) for conformance to FIPS 140 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
GnuTLS
GnuTLS (, the GNU Transport Layer Security Library) is a free software implementation of the TLS, SSL and DTLS protocols. It offers an application programming interface (API) for applications to enable secure communication over the network transport layer, as well as interfaces to access X.509, PKCS #12, OpenPGP and other structures. Features GnuTLS consists of a library that allows client applications to start secure sessions using the available protocols. It also provides command-line tools, including an X.509 certificate manager, a test client and server, and random key and password generators. GnuTLS has the following features: * TLS 1.3, TLS 1.2, TLS 1.1, TLS 1.0, and SSL 3.0 protocols * Datagram TLS (DTLS) 1.2, and DTLS 1.0, protocols * TLS-SRP: Secure remote password protocol (SRP) for TLS authentication * TLS-PSK: Pre-shared key (PSK) for TLS authentication * X.509 and OpenPGP certificate handling * CPU assisted cryptography and cryptographic accelerator support ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
OpenSSL
OpenSSL is a software library for applications that provide secure communications over computer networks against eavesdropping, and identify the party at the other end. It is widely used by Internet servers, including the majority of HTTPS websites. OpenSSL contains an open-source implementation of the SSL and TLS protocols. The core library, written in the C programming language, implements basic cryptographic functions and provides various utility functions. Wrappers allowing the use of the OpenSSL library in a variety of computer languages are available. The OpenSSL Software Foundation (OSF) represents the OpenSSL project in most legal capacities including contributor license agreements, managing donations, and so on. OpenSSL Software Services (OSS) also represents the OpenSSL project for support contracts. OpenSSL is available for most Unix-like operating systems (including Linux, macOS, and BSD), Microsoft Windows and OpenVMS. Project history The OpenSSL project wa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Birthday Attack
A birthday attack is a bruteforce collision attack that exploits the mathematics behind the birthday problem in probability theory. This attack can be used to abuse communication between two or more parties. The attack depends on the higher likelihood of collisions found between random attack attempts and a fixed degree of permutations ( pigeonholes). Let H be the number of possible values of a hash function, with H=2^l. With a birthday attack, it is possible to find a collision of a hash function with 50% chance in \sqrt = 2^, where l is the bit length of the hash output, and with 2^ being the classical preimage resistance security with the same probability. There is a general (though disputed) result that quantum computers can perform birthday attacks, thus breaking collision resistance, in \sqrt = 2^. Although there are some digital signature vulnerabilities associated with the birthday attack, it cannot be used to break an encryption scheme any faster than a brute-for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Collision Attack
In cryptography, a collision attack on a cryptographic hash tries to find two inputs producing the same hash value, i.e. a hash collision. This is in contrast to a preimage attack where a specific target hash value is specified. There are roughly two types of collision attacks: ;Classical collision attack: Find two different messages ''m''1 and ''m''2 such that ''hash''(''m''1) = ''hash''(''m''2). More generally: ;Chosen-prefix collision attack: Given two different prefixes ''p''1 and ''p''2, find two suffixes ''s''1 and ''s''2 such that ''hash''(''p''1 ∥ ''s''1) = ''hash''(''p''2 ∥ ''s''2), where ∥ denotes the concatenation operation. Classical collision attack Much like symmetric-key ciphers are vulnerable to brute force attacks, every cryptographic hash function is inherently vulnerable to collisions using a birthday attack. Due to the birthday problem, these attacks are much faster than a brute force would be. A hash of ''n'' bits can be broken in 2''n''/2 time steps (e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Time Complexity
In theoretical computer science, the time complexity is the computational complexity that describes the amount of computer time it takes to run an algorithm. Time complexity is commonly estimated by counting the number of elementary operations performed by the algorithm, supposing that each elementary operation takes a fixed amount of time to perform. Thus, the amount of time taken and the number of elementary operations performed by the algorithm are taken to be related by a constant factor. Since an algorithm's running time may vary among different inputs of the same size, one commonly considers the worst-case time complexity, which is the maximum amount of time required for inputs of a given size. Less common, and usually specified explicitly, is the average-case complexity, which is the average of the time taken on inputs of a given size (this makes sense because there are only a finite number of possible inputs of a given size). In both cases, the time complexity is gene ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Preimage Attack
In cryptography, a preimage attack on cryptographic hash functions tries to find a message that has a specific hash value. A cryptographic hash function should resist attacks on its preimage (set of possible inputs). In the context of attack, there are two types of preimage resistance: * ''preimage resistance'': for essentially all pre-specified outputs, it is computationally infeasible to find any input that hashes to that output; i.e., given , it is difficult to find an such that . * ''second-preimage resistance'': for a specified input, it is computationally infeasible to find another input which produces the same output; i.e., given , it is difficult to find a second input such that . These can be compared with a collision resistance, in which it is computationally infeasible to find any two distinct inputs , that hash to the same output; i.e., such that . Collision resistance implies second-preimage resistance. Second-preimage resistance implies preimage resistance only ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
