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.)

Introduction

Introduction, The Introduction, Intro, or The Intro may refer to:

Intro (R&B group)

Intro is an American R&B trio from Brooklyn, New York City, New York. The trio consisted of members Jeff Sanders, Clinton "Buddy" Wike and lead singer/songwriter Kenny Greene. Intro released two albums (for Atlantic Records): 1993's Intro and their second album, 1995's New Life. The group had a string of US hits in the 1990s. The hits included the singles "Let Me Be The One", the Stevie Wonder cover "Ribbon in the Sky", "Funny How Time Flies" and their highest charting hit, "Come Inside".

Intro's Kenny Greene died from complications of AIDS in 2001. Intro recently emerged as a quintet consisting of Clinton "Buddy" Wike, Jeff Sanders, Ramon Adams and Eric Pruitt. Adams departed in 2014, with the group back down to its lineup as a trio. They are currently recording a new album to be released in 2015. The group released a new single in 2013 called "I Didn't Sleep With Her" and a new single "Lucky" in October 2014.

Discography

Albums

Singles

References

Introduction (music)

In music, the introduction is a passage or section which opens a movement or a separate piece, preceding the theme or lyrics. In popular music this is often abbreviated as intro. The introduction establishes melodic, harmonic, and/or rhythmic material related to the main body of a piece.

Introductions may consist of an ostinato that is used in the following music, an important chord or progression that establishes the tonality and groove for the following music, or they may be important but disguised or out-of-context motivic or thematic material. As such the introduction may be the first statement of primary or other important material, may be related to but different from the primary or other important material, or may bear little relation to any other material.

A common introduction to a rubato ballad is a dominant seventh chord with fermata, Play  an introduction that works for many songs is the last four or eight measures of the song, Play  while a common introduction to the twelve-bar blues is a single chorus. Play