# MDC-2

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[1]. The length of the output hash depends on the underlying block cipher used.

## Algorithm

For a given message M to hash and a given block cipher encryption function E, the MDC-2 algorithm proceed as followed. Let n be the block length, A1,B1 two different constants of size n. If M = M1 | | .. | Mm where each Mi has size n, then the hash Vm | | Wm of the message is given by:

• for i = 1 to m:
• $V_i = M_i \oplus E(M_i,A_i)$
• $W_i = M_i \oplus E(M_i,B_i)$
• $V_i^L || V_i^R = V_i$
• $W_i^L || W_i^R = W_i$
• $A_{i+1} = V_i^R||W_i^L$
• $B_{i+1} = W_i^R||V_i^L$
• return Am + 1 | | Bm + 1

## 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:

``` MDC2("The quick brown fox jumps over the lazy dog")
= 000ed54e093d61679aefbeae05bfe33a
```

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

``` MDC2("The quick brown fox jumps over the lazy cog")
= 775f59f8e51aec29c57ac6ab850d58e8
```

The hash of the zero-length string is:

``` MDC2("")
= 52525252525252522525252525252525
```

## 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.

But the maximum lifespan of 20 years from filing date means that the U.S. Patent 4,908,861 could not have lasted beyond August 28, 2007 ; in fact it has expired in 2002[2], because IBM has not paid the renewal fee. The same goes for the Canadian patent. There is no patent for Europe.
This means that MDC2 can be freely used.

## Notes

1. ^ Steinberger, John (June 23, 2007). "The Collision Intractability of MDC-2 in the Ideal-Cipher Model". Advances in Cryptology - EUROCRYPT 2007. Springer-Verlag. pp. 34–51. doi:http://dx.doi.org/10.1007/978-3-540-72540-4_3. Retrieved January 31, 2008.
2. ^ USPTO - Patent Maintenance Fees. United States Patent Office. March 13, 2002. Retrieved 2008-01-31  (Click on "Bibliographic data".)

Wikimedia Foundation. 2010.

### См. также в других словарях:

• MDC — usually refers to: Movement for Democratic Change – Tsvangirai (MDC T), a Zimbabwean political party Movement for Democratic Change (pre 2005), a former Zimbabwean political party that split in 2005 into the MDC T and MDC M Movement for… …   Wikipedia

• MDC — (Motorola Data Communications) цифровой низкоскоростной протокол обмена. MDC монодансилкадаверин, производное кадаверина, ингибитор ферментов. MDC макрофагальный хемокин CCL22. MDC (англ. modification detection code) код проверки целостности …   Википедия

• MDC — son unas siglas que pueden referirse a: El Aeropuerto Internacional Sam Ratulangi, también conocido como «MDC», según el código de aeropuertos de IATA. La banda de hardcore punk estadounidense MDC. El partido político francés MDC (Mouvement des… …   Wikipedia Español

• MDC — ist die Abkürzung für Major Diagnostic Categories, die Hauptdiagnosegruppen im Diagnosis Related Groups Abrechnungssystem in der Medizin Flughafen Manado in Indonesien (IATA Code) Max Delbrück Centrum für Molekulare Medizin in Berlin Buch MDC,… …   Deutsch Wikipedia

• MDC — Cette page d’homonymie répertorie les différents sujets et articles partageant un même nom.   Sigles d’une seule lettre   Sigles de deux lettres > Sigles de trois lettres   Sigles de quatre lettres …   Wikipédia en Français

• MDC — material distribution center (MDC) A postal supply center that stocks retail supplies and equipment, forms and directives, spare parts, and expendable items …   Glossary of postal terms

• MDC — abbrev Movement for Democratic Change * * * MDC (no periods), more developed country: »The MDCs should make research facilities…available to the LDCs (Annual Register) …   Useful english dictionary

• MDC — abbreviation more developed country …   New Collegiate Dictionary

• MDC — Movement For Democratic Change (Governmental » Politics) *** M D C Holdings, Inc. (Business » NYSE Symbols) * Metropolitan District Commission (Governmental » State & Local) * Macrophage Derived Chemokine (Miscellaneous » Food) * Major Diagnostic …   Abbreviations dictionary

• MDC — macrophage derived chemokine; major diagnostic categories; metalloprotease disintegrin cysteine [ rich protein]; Metoprolol in Dilated Cardiomyopathy [trial]; minimum detectable concentration; monocyte depleted mononuclear cell; Multicenter… …   Medical dictionary

### Поделиться ссылкой на выделенное

##### Прямая ссылка:
Нажмите правой клавишей мыши и выберите «Копировать ссылку»