MDC

MDC may refer to:

MDC-2

In cryptography, MDC-2 (Modification Detection Code 2, sometimes called Meyer-Schilling) is a cryptographic hash function. MDC-2 is a hash function based on a block cipher with a proof of security in the ideal-cipher model. The length of the output hash depends on the underlying block cipher used.

Algorithm

For a given message to hash and a given block cipher encryption function , the MDC-2 algorithm proceeds as follows. Let be the block length, two different constants of size . If where each has size , then the hash of the message is given by:

for to :

• 
• 
• 
• 
• 
• 

return

MDC-2DES hashes

When MDC-2 uses the DES block cipher, the 128-bit (16-byte) MDC-2 hashes are typically represented as 32-digit hexadecimal numbers. The following demonstrates a 43-byte ASCII input and the corresponding MDC-2 hash:

Even a small change in the message will (with probability) result in a completely different hash, e.g. changing d to c:

The hash of the zero-length string is:

Patent issues

MDC-2 was covered by U.S. Patent 4,908,861, issued on March 13, 1990 but filed by IBM on August 28, 1987.
For this reason, support for MDC-2 has been disabled in OpenSSL on most Linux distributions and is not implemented by many other cryptographic libraries.

One-way compression function

In cryptography, a one-way compression function is a function that transforms two fixed-length inputs into a fixed-length output. The transformation is "one-way", meaning that it is difficult given a particular output to compute inputs which compress to that output. One-way compression functions are not related to data compression, which by definition can be inverted exactly (lossless compression) or approximately (lossy compression) to the original data.

One-way compression functions are for instance used in the Merkle–Damgård construction inside cryptographic hash functions.

One-way compression functions are often built from block ciphers. Some methods to turn any normal block cipher into a one-way compression function are Davies–Meyer, Matyas–Meyer–Oseas, Miyaguchi–Preneel (single-block-length compression functions) and MDC-2/Meyer–Schilling, MDC-4, Hirose (double-block-length compression functions). These methods are described in detail further down. (MDC-2 is also the name of a hash function patented by IBM.)

Acids in wine

The acids in wine are an important component in both winemaking and the finished product of wine. They are present in both grapes and wine, having direct influences on the color, balance and taste of the wine as well as the growth and vitality of yeast during fermentation and protecting the wine from bacteria. The measure of the amount of acidity in wine is known as the “titratable acidity” or “total acidity”, which refers to the test that yields the total of all acids present, while strength of acidity is measured according to pH, with most wines having a pH between 2.9 and 3.9. Generally, the lower the pH, the higher the acidity in the wine. However, there is no direct connection between total acidity and pH (it is possible to find wines with a high pH for wine and high acidity). In wine tasting, the term “acidity” refers to the fresh, tart and sour attributes of the wine which are evaluated in relation to how well the acidity balances out the sweetness and bitter components of the wine such as tannins. Three primary acids are found in wine grapes: tartaric, malic and citric acids. During the course of winemaking and in the finished wines, acetic, butyric, lactic and succinic acids can play significant roles. Most of the acids involved with wine are fixed acids with the notable exception of acetic acid, mostly found in vinegar, which is volatile and can contribute to the wine fault known as volatile acidity. Sometimes, additional acids, such as ascorbic, sorbic and sulfurous acids, are used in winemaking.

Acid (disambiguation)

An acid is any chemical compound that, when dissolved in water, gives a solution with a pH less than 7.0.

Acid or ACID may also refer to:

Science

Computing

Music

Genres

Bands

Acid house

Acid house is a subgenre of house music developed around the mid-1980s by DJs from Chicago. The defining feature of a "squelching" bass sound was produced using the Roland TB-303 electronic synthesizer-sequencer. Acid house spread to the United Kingdom and continental Europe, where it was played by DJs in the acid house and later rave scenes. By the late 1980s, acid house had moved into the British mainstream, where it had some influence on pop and dance styles.

Acid house brought house music to a worldwide audience. The influence of acid house can be heard on later styles of dance music including trance, Goa trance, psychedelic trance, breakbeat, big beat, techno and trip hop.

Characteristics

Acid house's minimalist production aesthetic combined house music's ubiquitous programmed 4/4 beat with the electronic ‘squelch' sound produced by the Roland TB-303 electronic synthesizer-sequencer by constantly modulating its frequency and resonance controls to create 'movement' in otherwise simple bass patterns. Other elements, such as synthetic strings and stabs, were usually minimal. Sometimes tracks were instrumentals such as Phuture's "Acid Tracks", or contained full vocal performances such as Pierre's Pfantasy Club's "Dream Girl", while others were essentially instrumentals complemented by the odd spoken word 'drop-in', such as Phuture's "Slam".