freebsd-nq/lib/libmd/ripemd.3

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.Dd February 26, 1999
.Dt RIPEMD 3
.Os FreeBSD 4.0
.Sh NAME
.Nm RIPEMD160_Init ,
.Nm RIPEMD160_Update ,
.Nm RIPEMD160_Final ,
.Nm RIPEMD160_End ,
.Nm RIPEMD160_File ,
.Nm RIPEMD160_Data
.Nd calculate the RIPEMD160 message digest
.Sh LIBRARY
.Lb libmd
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <ripemd.h>
.Ft void
.Fn RIPEMD160_Init "RIPEMD160_CTX *context"
.Ft void
.Fn RIPEMD160_Update "RIPEMD160_CTX *context" "const unsigned char *data" "unsigned int len"
.Ft void
.Fn RIPEMD160_Final "unsigned char digest[20]" "RIPEMD160_CTX *context"
.Ft "char *"
.Fn RIPEMD160_End "RIPEMD160_CTX *context" "char *buf"
.Ft "char *"
.Fn RIPEMD160_File "const char *filename" "char *buf"
.Ft "char *"
.Fn RIPEMD160_Data "const unsigned char *data" "unsigned int len" "char *buf"
.Sh DESCRIPTION
The
.Li RIPEMD160_
functions calculate a 160-bit cryptographic checksum (digest)
for any number of input bytes.  A cryptographic checksum is a one-way
hash function; that is, it is computationally impractical to find
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
The
.Fn RIPEMD160_Init  ,
.Fn RIPEMD160_Update ,
and
.Fn RIPEMD160_Final
functions are the core functions.  Allocate an RIPEMD160_CTX, initialize it with
.Fn RIPEMD160_Init ,
run over the data with
.Fn RIPEMD160_Update ,
and finally extract the result using
.Fn RIPEMD160_Final .
.Pp
.Fn RIPEMD160_End
is a wrapper for
.Fn RIPEMD160_Final
which converts the return value to a 41-character
(including the terminating '\e0')
.Tn ASCII
string which represents the 160 bits in hexadecimal.
.Pp
.Fn RIPEMD160_File
calculates the digest of a file, and uses 
.Fn RIPEMD160_End
to return the result.
If the file cannot be opened, a null pointer is returned.
.Fn RIPEMD160_Data
calculates the digest of a chunk of data in memory, and uses
.Fn RIPEMD160_End
to return the result.
.Pp
When using
.Fn RIPEMD160_End ,
.Fn RIPEMD160_File ,
or
.Fn RIPEMD160_Data ,
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 41 characters of buffer space.
.Sh SEE ALSO
.Xr md2 3 ,
.Xr md4 3 ,
.Xr md5 3 ,
.Xr sha 3
.Sh AUTHORS
The core hash routines were implemented by Eric Young based on the
published
.Tn RIPEMD160
specification.
.Sh HISTORY
These functions appeared in
.Fx 4.0 .
.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.