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Diffstat (limited to 'lib/libmd/mdX.3')
| -rw-r--r-- | lib/libmd/mdX.3 | 167 |
1 files changed, 167 insertions, 0 deletions
diff --git a/lib/libmd/mdX.3 b/lib/libmd/mdX.3 new file mode 100644 index 0000000..ebd8b30 --- /dev/null +++ b/lib/libmd/mdX.3 @@ -0,0 +1,167 @@ +.\" +.\" ---------------------------------------------------------------------------- +.\" "THE BEER-WARE LICENSE" (Revision 42): +.\" <phk@login.dkuug.dk> wrote this file. As long as you retain this notice you +.\" can do whatever you want with this stuff. If we meet some day, and you think +.\" this stuff is worth it, you can buy me a beer in return. Poul-Henning Kamp +.\" ---------------------------------------------------------------------------- +.\" +.\" $FreeBSD$ +.\" +.Dd February 11, 1999 +.Dt MDX 3 +.Os FreeBSD 2 +.Sh NAME +.Nm MDXInit , +.Nm MDXUpdate , +.Nm MDXPad , +.Nm MDXFinal , +.Nm MDXEnd , +.Nm MDXFile , +.Nm MDXData +.Nd calculate the RSA Data Security, Inc., ``MDX'' message digest +.Sh SYNOPSIS +.Fd #include <sys/types.h> +.Fd #include <mdX.h> +.Ft void +.Fn MDXInit "MDX_CTX *context" +.Ft void +.Fn MDXUpdate "MDX_CTX *context" "const unsigned char *data" "unsigned int len" +.Ft void +.Fn MDXPad "MDX_CTX *context" +.Ft void +.Fn MDXFinal "unsigned char digest[16]" "MDX_CTX *context" +.Ft "char *" +.Fn MDXEnd "MDX_CTX *context" "char *buf" +.Ft "char *" +.Fn MDXFile "const char *filename" "char *buf" +.Ft "char *" +.Fn MDXData "const unsigned char *data" "unsigned int len" "char *buf" +.Sh DESCRIPTION +The MDX 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 input corresponding to a particular output. This net result is +a ``fingerprint'' of the input-data, which doesn't disclose the actual +input. +.Pp +MD2 is the slowest, MD4 is the fastest and MD5 is somewhere in the middle. +MD2 can only be used for Privacy-Enhanced Mail. +MD4 has now been broken; it should only be used where necessary for +backward compatibility. +MD5 has not yet (1999-02-11) been broken, but sufficient attacks have been +made that its security is in some doubt. 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. +.Pp +The +.Fn MDXInit , +.Fn MDXUpdate , +and +.Fn MDXFinal +functions are the core functions. Allocate an MDX_CTX, initialize it with +.Fn MDXInit , +run over the data with +.Fn MDXUpdate , +and finally extract the result using +.Fn MDXFinal . +.Pp +.Fn MDXPad +can be used to pad message data in same way +as done by +.Fn MDXFinal +without terminating calculation. +.Pp +.Fn MDXEnd +is a wrapper for +.Fn MDXFinal +which converts the return value to a 33-character +(including the terminating '\e0') +.Tn ASCII +string which represents the 128 bits in hexadecimal. +.Pp +.Fn MDXFile +calculates the digest of a file, and uses +.Fn MDXEnd +to return the result. +If the file cannot be opened, a null pointer is returned. +.Fn MDXData +calculates the digest of a chunk of data in memory, and uses +.Fn MDXEnd +to return the result. +.Pp +When using +.Fn MDXEnd , +.Fn MDXFile , +or +.Fn MDXData , +the +.Ar buf +argument can be a null pointer, in which case the returned string +is allocated with +.Xr malloc 3 +and subsequently must be explicitly deallocated using +.Xr free 3 +after use. +If the +.Ar buf +argument is non-null it must point to at least 33 characters of buffer space. +.Sh SEE ALSO +.Xr md2 3 , +.Xr md4 3 , +.Xr md5 3 , +.Xr sha 3 +.Rs +.%A B. Kaliski +.%T The MD2 Message-Digest Algorithm +.%O RFC 1319 +.Re +.Rs +.%A R. Rivest +.%T The MD4 Message-Digest Algorithm +.%O RFC 1186 +.Re +.Rs +.%A R. Rivest +.%T The MD5 Message-Digest Algorithm +.%O RFC 1321 +.Re +.Rs +.%A RSA Laboratories +.%T Frequently Asked Questions About today's Cryptography +.%O \&<http://www.rsa.com/rsalabs/faq/> +.Re +.Rs +.%A H. Dobbertin +.%T Alf Swindles Ann +.%J CryptoBytes +.%N 1(3):5 +.%D 1995 +.Re +.Rs +.%A MJ. B. Robshaw +.%T On Recent Results for MD2, MD4 and MD5 +.%J RSA Laboratories Bulletin +.%N 4 +.%D November 12, 1996 +.Re +.Sh AUTHORS +The original MDX routines were developed by +.Tn RSA +Data Security, Inc., and published in the above references. +This code is derived directly from these implementations by +.An Poul-Henning Kamp Aq phk@login.dkuug.dk +.Pp +Phk ristede runen. +.Sh HISTORY +These functions appeared in +.Fx 2.0 . +.Sh BUGS +No method is known to exist which finds two files having the same hash value, +nor to find a file with a specific hash value. +There is on the other hand no guarantee that such a method doesn't exist. +.Pp +MD2 has only been licensed for use in Privacy Enhanced Mail. +Use MD4 or MD5 if that isn't what you're doing. +.Sh COPYRIGHT |
