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"THE BEER-WARE LICENSE" (Revision 42):
<phk (at] 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
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from FreeBSD Id: mdX.3,v 1.7 1996/10/22 16:28:56 phk Exp
.Dd September 24, 2005 .Dt MD2 3 .Os .Sh NAME .Nm MD2Init , .Nm MD2Update , .Nm MD2Final , .Nm MD2End , .Nm MD2File , .Nm MD2Data .Nd calculate the RSA Data Security, Inc., .Dq MD2 message digest .Sh LIBRARY .Lb libc .Sh SYNOPSIS n sys/types.h n mdX.h .Ft void .Fn MD2Init "MD2_CTX *context" .Ft void .Fn MD2Update "MD2_CTX *context" "const unsigned char *data" "unsigned int len" .Ft void .Fn MD2Final "unsigned char digest[16]" "MD2_CTX *context" .Ft "char *" .Fn MD2End "MD2_CTX *context" "char *buf" .Ft "char *" .Fn MD2File "const char *filename" "char *buf" .Ft "char *" .Fn MD2Data "const unsigned char *data" "unsigned int len" "char *buf" .Sh DESCRIPTION The MD2 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.
p The MD2 routines should not be used for any security-related purpose.
p The .Fn MD2Init , .Fn MD2Update , and .Fn MD2Final functions are the core functions. Allocate an MD2_CTX, initialize it with .Fn MD2Init , run over the data with .Fn MD2Update , and finally extract the result using .Fn MD2Final .
p .Fn MD2End is a wrapper for .Fn MD2Final which converts the return value to a 33-character (including the terminating '\e0') ASCII string which represents the 128 bits in hexadecimal.
p .Fn MD2File calculates the digest of a file, and uses .Fn MD2End to return the result. If the file cannot be opened, a null pointer is returned. .Fn MD2Data calculates the digest of a chunk of data in memory, and uses .Fn MD2End to return the result.
p When using .Fn MD2End , .Fn MD2File , or .Fn MD2Data , 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 md4 3 , .Xr md5 3 , .Xr openssl_MD2 3 , .Xr openssl_MD4 3 , .Xr openssl_MD5 3 , .Rs .%A B. Kaliski .%T The MD2 Message-Digest Algorithm .%O RFC 1319 .Re .Rs .%A RSA Laboratories .%T Frequently Asked Questions About today's Cryptography .Re .Sh HISTORY These functions appeared in .Nx 1.3 . .Sh AUTHORS .An -nosplit The original MD2 routines were developed by .An RSA Data Security, Inc. , and published in the above references. This code is a public domain implementation by .An Andrew Brown . .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.
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