'\" t
.\"	aegis - project change supervisor
.\"	Copyright (C) 1994, 1995 Peter Miller;
.\"	All rights reserved.
.\"
.\"	This program is free software; you can redistribute it and/or modify
.\"	it under the terms of the GNU General Public License as published by
.\"	the Free Software Foundation; either version 2 of the License, or
.\"	(at your option) any later version.
.\"
.\"	This program is distributed in the hope that it will be useful,
.\"	but WITHOUT ANY WARRANTY; without even the implied warranty of
.\"	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
.\"	GNU General Public License for more details.
.\"
.\"	You should have received a copy of the GNU General Public License
.\"	along with this program; if not, write to the Free Software
.\"	Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
.\"
.\" MANIFEST: manual entry for the aefp command
.\"
.ds n) aefp
.TH \*(n) 1 \*(N) "Reference Manual"
.SH NAME
\*(n) \- calculate file fingerprint
.XX "aefp(1)" "calculate file fingerprint"
.SH SYNOPSIS
.B \*(n)
[
.IR option \&...
][
.IR filename \&...
]
.br
.B \*(n)
.B -Help
.br
.B \*(n)
.B -VERSion
.SH DESCRIPTION
The
.I \*(n)
program is used to
calculate the fingerprints of files.
A fingerprint is a hash of the contents of a file.
The default fingerprint is cryptographically strong,
so the probability of two different files having the
same fingerprint is less than 1 in 2**200.
.PP
The fingerprint is based on Dan Berstien <djb@silverton.berkeley.edu>
public domain fingerprint 0.50 beta package 930809,
posted to the alt.sources newsgroup.
This program produces identical results;
the expected test results were generated using Dan's package.
.PP
The
fingerprint is a base-64-sanely-encoded fingerprint of the input.
Imagine this fingerprint as something universal and permanent.
A fingerprint is 76 characters long, containing the following:
.TP 4n
1.
A Snefru-8 (version 2.5, 8 passes, 512->256) hash.
(Derived from the Xerox Secure Hash Function.)
.TP 4n
2.
An MD5 hash, as per RFC 1321.
(Derived from the RSADSI MD5 Message-Digest Algorithm.)
.TP 4n
3.
A CRC checksum, as in the new cksum utility.
.TP 4n
4.
Length modulo 2^40.
.PP
The output format is not expected to be compatible with anything.
However,
options are available to produce
the purported output of Merkle's snefru program,
the purported output of RSADSI's mddriver -x,
or the purported output of the POSIX cksum program.
.PP
If no files are named as input,
the standard input will be used.
The special file name ``-'' is understood to mean the standard input.
.br
.ne 1i
.SH OPTIONS
The following options are understood:
.TP 8n
.B -Checksum
Print the CRC32 checksum and length of the named file(s).
.TP 8n
.B -Identifier
Print a condensed form of the fingerprint (obtained by performing a
CRC32 checksum on the full fingerprint described above - a definite
overkill).
This is an 8-digit hexadecimal number,
useful for generating unique short identifiers out of long names.
The first character is forced to be a letter (g-p),
so there is no problem in using the output as a variable name.
.TP 8n
.B -Help
.br
Provide some help with using the
.I \*(n)
program.
.TP 8n
.B -Message_Digest
Print the
RSA Data Security, Inc. MD5 Message-Digest Algorithm
hash of the named file(s).
.TP 8n
.B -Snefru
Print the Snefru hash of the named file(s),
derived from the Xerox Secure Hash Function.
.TP 8n
.B -VERSion
.br
Print the version of the
.I \*(n)
program being executed.
.PP
All other options will produce a diagnostic error.
.so o__rules.so
.so z_exit.so
.so z_cr.so
.PP
Portions of this program are derived from sources from other people,
sometimes with liberal copyrights, and sometimes in the public domain.
These include:
.TP 8n
Dan Bernstien
See
.I common/fp/README
for details.
.TP 8n
Gary S Brown.
See
.I common/fp/crc32.c
for details.
.TP 8n
RSA Data Security, Inc.
See
.I common/fp/md5.c
for details.
.TP 8n
Xerox Corporation
See
.I common/fp/snefru.c
for details.
.PP
In addition to the above copyright holders,
there have been numerous authors and contributors,
see the named files for details.
Files names are relative to the root of the
.I aegis
distribution.