1.\" 2.\" ---------------------------------------------------------------------------- 3.\" "THE BEER-WARE LICENSE" (Revision 42): 4.\" <phk@login.dkuug.dk> wrote this file. As long as you retain this notice you 5.\" can do whatever you want with this stuff. If we meet some day, and you think 6.\" this stuff is worth it, you can buy me a beer in return. Poul-Henning Kamp 7.\" ---------------------------------------------------------------------------- 8.\" 9.\" $FreeBSD$ 10.\" 11.Dd July 14, 1994 12.Dt MDX 3 13.Os FreeBSD 2 14.Sh NAME 15.Nm MDXInit , 16.Nm MDXUpdate , 17.Nm MDXFinal , 18.Nm MDXEnd , 19.Nm MDXFile , 20.Nm MDXData . 21.Nd calculate ``MDX'' cryptographic checksum 22.Sh SYNOPSIS 23.Fd #include <mdX.h> 24.Ft void 25.Fn MDXInit "MDX_CTX *context" 26.Ft void 27.Fn MDXUpdate "MDX_CTX *context" "unsigned char *data" "unsigned int len" 28.Ft void 29.Fn MDXFinal "unsigned char digest[16]" "MDX_CTX *context" 30.Ft "char *" 31.Fn MDXEnd "MDX_CTX *context" 32.Ft "char *" 33.Fn MDXFile "char *filename" 34.Ft "char *" 35.Fn MDXData "unsigned char *data" "unsigned int len" 36.Sh DESCRIPTION 37The MDX functions calculate a 128-bit cryptographic checksum (digest) 38for any number of input bytes. A cryptographic checksum is a one-way 39hash-function, that is, you cannot find (except by exhaustive search) 40the input corresponding to a particular output. This net result is 41a ``fingerprint'' of the input-data, which doesn't disclose the actual 42input. 43 44MD2 is the slowest, MD4 is the fastest and MD5 is somewhere in the middle. 45MD2 can only be used for Privacy-Enhanced Mail. 46MD4 has been critizised for being to weak, and MD5 was developed as a 47response to this as ``MD4 with safety-belts''. If in doubt, use MD5. 48 49The 50.Fn MDXInit , 51.Fn MDXUpdate 52and 53.Fn MDXFinal 54functions are the core functions. Allocate a MDX_CTX, initialize it with 55.Fn MDXInit 56run over the data with 57.Fn MDXUpdate 58and finally extract the result using 59.Fn MDXFinal . 60 61.Fn MDXEnd 62is identical to 63.Fn MDXFinal , 64except the return is in ASCII-HEX in a 65string allocated with 66.Xr malloc 3 . 67 68.Fn MDXFile 69calculates the digest of a file, and returns the ASCII-HEX result. 70In case the file cannot be opened, NULL is returned. 71 72.Fn MDXData 73calculates the digest of a chunk of data in memory, and returns the ASCII-HEX 74result. 75 76When using 77.Fn MDXEnd , 78.Fn MDXFile 79and 80.Fn MDXData , 81the returned string must be explicitly deallocated using 82.Xr free 3 83after use. 84.Sh SEE ALSO 85.Xr md2 3 , 86.Xr md4 3 , 87.Xr md5 3 88.Pp 89ISOC 90Internet Request For Comments 91.%T RFC1319 , 92.%T RFC1320 93and 94.%T RFC1321 . 95.Pp 96RSA Laboratories 97.%T Frequently Asked Questions About today's Cryptography . 98.Sh AUTHOR 99The MD2, MD4 and MD5 is designed and written by Ron Rivest and published in 100the above RFC's, including a reference implementation of each algorithm. 101 102This code is derived directly from these implementations by Poul-Henning Kamp 103<phk@login.dkuug.dk> 104 105Phk ristede runen. 106.Sh HISTORY 107These functions appeared in 108.Em FreeBSD-2.0 109.Sh BUGS 110No method is known to exist which finds two files having the same hash value, 111nor to find a file with a specific hash value. 112There is on the other hand no guarantee that such a method doesn't exist. 113 114MD2 can only be used for Privacy Enhanced Mail. 115Use MD4 or MD5 if that isn't what you're doing. 116.Sh COPYRIGHT 117