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 proceeds as follows. Let $n$ be the block length, $A_{1},B_{1}$ two different constants of size $n$ . If $M=M_{1}||..||M_{m}$ where each $M_{i}$ has size $n$ , then the hash $V_{m}||W_{m}$ 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 $A_{{m+1}}||B_{{m+1}}$

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 MDC-2 can be freely used.

Notes

↑ 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:10.1007/978-3-540-72540-4_3. Retrieved January 31, 2008.
↑ "USPTO - Patent Maintenance Fees". United States Patent Office. March 13, 2002. Retrieved 2008-01-31. (Click on "Bibliographic data".)

Cryptographic hash functions & message authentication codes

List Comparison Known attacks

Common functions	MD5 SHA-1 SHA-2 SHA-3 BLAKE2

SHA-3 finalists	BLAKE Grøstl JH Skein Keccak (winner)

Other functions	ECOH FSB GOST HAS-160 HAVAL Kupyna LM hash MD2 MD4 MD5 MD6 MDC-2 N-Hash RIPEMD RadioGatún SWIFFT SipHash Snefru Streebog Tiger VSH WHIRLPOOL

Key derivation functions	bcrypt crypt PBKDF2 scrypt Argon2 Lyra2

MAC functions	DAA CBC-MAC HMAC OMAC/CMAC PMAC VMAC UMAC Poly1305

Authenticated encryption modes	CCM CWC EAX GCM IAPM OCB

Attacks	Collision attack Preimage attack Birthday attack Brute force attack Rainbow table Side-channel attack Length extension attack

Design	Avalanche effect Hash collision Merkle–Damgård construction

Standardization	CRYPTREC NESSIE NIST hash function competition

Utilization	Hash-based cryptography Key stretching Merkle tree Message authentication Proof of work Salt

Cryptography

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MDC-2

Algorithm

MDC-2DES hashes

Patent issues

See also

Notes