MD4(3) BSD Programmer's Manual MD4(3)
MD4Init, MD4Update, MD4Pad, MD4Final, MD4Transform, MD4End, MD4File, MD4FileChunk, MD4Data - calculate the RSA Data Security, Inc., ``MD4'' message digest
#include <sys/types.h> #include <md4.h> void MD4Init(MD4_CTX *context); void MD4Update(MD4_CTX *context, const u_int8_t *data, size_t len); void MD4Pad(MD4_CTX *context); void MD4Final(u_int8_t digest[MD4_DIGEST_LENGTH], MD4_CTX *context); void MD4Transform(u_int32_t state, u_int8_t block[MD4_BLOCK_LENGTH]); char * MD4End(MD4_CTX *context, char *buf); char * MD4File(const char *filename, char *buf); char * MD4FileChunk(const char *filename, char *buf, off_t offset, off_t length); char * MD4Data(const u_int8_t *data, size_t len, char *buf);
The MD4 functions calculate a 128-bit cryptographic checksum (digest) for any number of input bytes. A cryptographic checksum is a one-way hash- function, that is, you cannot find (except by exhaustive search) the in- put corresponding to a particular output. This net result is a "fingerprint" of the input-data, which doesn't disclose the actual input. MD4 has been broken; it should only be used where necessary for backward compatibility. MD5 has not yet (1999-02-11) been broken, but recent at- tacks have cast some doubt on its security properties. The attacks on both MD4 and MD5 are both in the nature of finding "collisions" - that is, multiple inputs which hash to the same value; it is still unlikely for an attacker to be able to determine the exact original input given a hash value. The MD4Init(), MD4Update(), and MD4Final() functions are the core func- tions. Allocate an MD4_CTX, initialize it with MD4Init(), run over the data with MD4Update(), and finally extract the result using MD4Final(). The MD4Pad() function can be used to apply padding to the message digest as in MD4Final(), but the current context can still be used with MD4Update(). The MD4Transform() function is used by MD4Update() to hash 512-bit blocks and forms the core of the algorithm. Most programs should use the inter- face provided by MD4Init(), MD4Update() and MD4Final() instead of calling MD4Transform() directly. MD4End() is a wrapper for MD4Final() which converts the return value to an MD4_DIGEST_STRING_LENGTH-character (including the terminating '\0') ASCII string which represents the 128 bits in hexadecimal. MD4File() calculates the digest of a file, and uses MD4End() to return the result. If the file cannot be opened, a null pointer is returned. MD4FileChunk() behaves like MD4File() but calculates the digest only for that portion of the file starting at offset and continuing for length bytes or until end of file is reached, whichever comes first. A zero length can be specified to read until end of file. A negative length or offset will be ignored. MD4Data() calculates the digest of a chunk of data in memory, and uses MD4End() to return the result. When using MD4End(), MD4File(), MD4FileChunk(), or MD4Data(), the buf ar- gument can be a null pointer, in which case the returned string is allo- cated with malloc(3) and subsequently must be explicitly deallocated us- ing free(3) after use. If the buf argument is non-null it must point to at least MD4_DIGEST_STRING_LENGTH characters of buffer space.
cksum(1), md5(1), adler32(3), md5(3), rmd160(3), sfv(3), sha1(3), sha2(3), suma(3), tiger(3), whirlpool(3) R. Rivest, The MD4 Message-Digest Algorithm, RFC 1186. R. Rivest, The MD5 Message-Digest Algorithm, RFC 1321. RSA Laboratories, Frequently Asked Questions About today's Cryptography, <http://www.rsa.com/rsalabs/faq/>. H. Dobbertin, "Alf Swindles Ann", CryptoBytes, 1(3):5, 1995. MJ. B. Robshaw, "On Recent Results for MD4 and MD5", RSA Laboratories Bulletin, 4, November 12, 1996. Hans Dobbertin, Cryptanalysis of MD5 Compress.
These functions appeared in OpenBSD 2.0.
The original MD4 routines were developed by RSA Data Security, Inc., and published in the above references. This code is derived from a public domain implementation written by Colin Plumb. The MD4End(), MD4File(), MD4FileChunk(), and MD4Data() helper functions are derived from code written by Poul-Henning Kamp.
Collisions have been found for the full versions of both MD4 and MD5 as well as strong attacks against the SHA-0 and SHA-1 family. The use of sha2(3), or rmd160(3) is recommended instead. MirOS BSD #10-current April 29, 2004 1
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