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.\" ========================================================================
.\"
.IX Title "MD4 3pm"
.TH MD4 3pm "2018-11-01" "perl v5.28.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
Digest::MD4 \- Perl interface to the MD4 Algorithm
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 2
\& # Functional style
\& use Digest::MD4 qw(md4 md4_hex md4_base64);
\&
\& $digest = md4($data);
\& $digest = md4_hex($data);
\& $digest = md4_base64($data);
\&
\& # OO style
\& use Digest::MD4;
\&
\& $ctx = Digest::MD4\->new;
\&
\& $ctx\->add($data);
\& $ctx\->addfile(*FILE);
\&
\& $digest = $ctx\->digest;
\& $digest = $ctx\->hexdigest;
\& $digest = $ctx\->b64digest;
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The \f(CW\*(C`Digest::MD4\*(C'\fR module allows you to use the \s-1RSA\s0 Data Security
Inc. \s-1MD4\s0 Message Digest algorithm from within Perl programs.  The
algorithm takes as input a message of arbitrary length and produces as
output a 128\-bit \*(L"fingerprint\*(R" or \*(L"message digest\*(R" of the input.
.PP
The \f(CW\*(C`Digest::MD4\*(C'\fR module provide a procedural interface for simple
use, as well as an object oriented interface that can handle messages
of arbitrary length and which can read files directly.
.SH "FUNCTIONS"
.IX Header "FUNCTIONS"
The following functions are provided by the \f(CW\*(C`Digest::MD4\*(C'\fR module.
None of these functions are exported by default.
.IP "md4($data,...)" 4
.IX Item "md4($data,...)"
This function will concatenate all arguments, calculate the \s-1MD4\s0 digest
of this \*(L"message\*(R", and return it in binary form.  The returned string
will be 16 bytes long.
.Sp
The result of md4(\*(L"a\*(R", \*(L"b\*(R", \*(L"c\*(R") will be exactly the same as the
result of md4(\*(L"abc\*(R").
.IP "md4_hex($data,...)" 4
.IX Item "md4_hex($data,...)"
Same as \fBmd4()\fR, but will return the digest in hexadecimal form. The
length of the returned string will be 32 and it will only contain
characters from this set: '0'..'9' and 'a'..'f'.
.IP "md4_base64($data,...)" 4
.IX Item "md4_base64($data,...)"
Same as \fBmd4()\fR, but will return the digest as a base64 encoded string.
The length of the returned string will be 22 and it will only contain
characters from this set: 'A'..'Z', 'a'..'z', '0'..'9', '+' and
\&'/'.
.Sp
Note that the base64 encoded string returned is not padded to be a
multiple of 4 bytes long.  If you want interoperability with other
base64 encoded md4 digests you might want to append the redundant
string \*(L"==\*(R" to the result.
.SH "METHODS"
.IX Header "METHODS"
The object oriented interface to \f(CW\*(C`Digest::MD4\*(C'\fR is described in this
section.  After a \f(CW\*(C`Digest::MD4\*(C'\fR object has been created, you will add
data to it and finally ask for the digest in a suitable format.  A
single object can be used to calculate multiple digests.
.PP
The following methods are provided:
.ie n .IP "$md4 = Digest::MD4\->new" 4
.el .IP "\f(CW$md4\fR = Digest::MD4\->new" 4
.IX Item "$md4 = Digest::MD4->new"
The constructor returns a new \f(CW\*(C`Digest::MD4\*(C'\fR object which encapsulate
the state of the \s-1MD4\s0 message-digest algorithm.
.Sp
If called as an instance method (i.e. \f(CW$md4\fR\->new) it will just reset the
state the object to the state of a newly created object.  No new
object is created in this case.
.ie n .IP "$md4\->reset" 4
.el .IP "\f(CW$md4\fR\->reset" 4
.IX Item "$md4->reset"
This is just an alias for \f(CW$md4\fR\->new.
.ie n .IP "$md4\->clone" 4
.el .IP "\f(CW$md4\fR\->clone" 4
.IX Item "$md4->clone"
This a copy of the \f(CW$md4\fR object. It is useful when you do not want to
destroy the digests state, but need an intermediate value of the
digest, e.g. when calculating digests iteratively on a continuous data
stream.  Example:
.Sp
.Vb 5
\&    my $md4 = Digest::MD4\->new;
\&    while (<>) {
\&        $md4\->add($_);
\&        print "Line $.: ", $md4\->clone\->hexdigest, "\en";
\&    }
.Ve
.ie n .IP "$md4\->add($data,...)" 4
.el .IP "\f(CW$md4\fR\->add($data,...)" 4
.IX Item "$md4->add($data,...)"
The \f(CW$data\fR provided as argument are appended to the message we
calculate the digest for.  The return value is the \f(CW$md4\fR object itself.
.Sp
All these lines will have the same effect on the state of the \f(CW$md4\fR
object:
.Sp
.Vb 4
\&    $md4\->add("a"); $md4\->add("b"); $md4\->add("c");
\&    $md4\->add("a")\->add("b")\->add("c");
\&    $md4\->add("a", "b", "c");
\&    $md4\->add("abc");
.Ve
.ie n .IP "$md4\->addfile($io_handle)" 4
.el .IP "\f(CW$md4\fR\->addfile($io_handle)" 4
.IX Item "$md4->addfile($io_handle)"
The \f(CW$io_handle\fR will be read until \s-1EOF\s0 and its content appended to the
message we calculate the digest for.  The return value is the \f(CW$md4\fR
object itself.
.Sp
The \fBaddfile()\fR method will \fBcroak()\fR if it fails reading data for some
reason.  If it croaks it is unpredictable what the state of the \f(CW$md4\fR
object will be in. The \fBaddfile()\fR method might have been able to read
the file partially before it failed.  It is probably wise to discard
or reset the \f(CW$md4\fR object if this occurs.
.Sp
In most cases you want to make sure that the \f(CW$io_handle\fR is in
\&\f(CW\*(C`binmode\*(C'\fR before you pass it as argument to the \fBaddfile()\fR method.
.ie n .IP "$md4\->digest" 4
.el .IP "\f(CW$md4\fR\->digest" 4
.IX Item "$md4->digest"
Return the binary digest for the message.  The returned string will be
16 bytes long.
.Sp
Note that the \f(CW\*(C`digest\*(C'\fR operation is effectively a destructive,
read-once operation. Once it has been performed, the \f(CW\*(C`Digest::MD4\*(C'\fR
object is automatically \f(CW\*(C`reset\*(C'\fR and can be used to calculate another
digest value.  Call \f(CW$md4\fR\->clone\->digest if you want to calculate the
digest without resetting the digest state.
.ie n .IP "$md4\->hexdigest" 4
.el .IP "\f(CW$md4\fR\->hexdigest" 4
.IX Item "$md4->hexdigest"
Same as \f(CW$md4\fR\->digest, but will return the digest in hexadecimal
form. The length of the returned string will be 32 and it will only
contain characters from this set: '0'..'9' and 'a'..'f'.
.ie n .IP "$md4\->b64digest" 4
.el .IP "\f(CW$md4\fR\->b64digest" 4
.IX Item "$md4->b64digest"
Same as \f(CW$md4\fR\->digest, but will return the digest as a base64 encoded
string.  The length of the returned string will be 22 and it will only
contain characters from this set: 'A'..'Z', 'a'..'z', '0'..'9', '+'
and '/'.
.Sp
The base64 encoded string returned is not padded to be a multiple of 4
bytes long.  If you want interoperability with other base64 encoded
md4 digests you might want to append the string \*(L"==\*(R" to the result.
.SH "EXAMPLES"
.IX Header "EXAMPLES"
The simplest way to use this library is to import the \fBmd4_hex()\fR
function (or one of its cousins):
.PP
.Vb 2
\&    use Digest::MD4 qw(md4_hex);
\&    print "Digest is ", md4_hex("foobarbaz"), "\en";
.Ve
.PP
The above example would print out the message:
.PP
.Vb 1
\&    Digest is b2b2b528f632f554ae9cb2c02c904eeb
.Ve
.PP
The same checksum can also be calculated in \s-1OO\s0 style:
.PP
.Vb 1
\&    use Digest::MD4;
\&    
\&    $md4 = Digest::MD4\->new;
\&    $md4\->add(\*(Aqfoo\*(Aq, \*(Aqbar\*(Aq);
\&    $md4\->add(\*(Aqbaz\*(Aq);
\&    $digest = $md4\->hexdigest;
\&    
\&    print "Digest is $digest\en";
.Ve
.PP
With \s-1OO\s0 style you can break the message arbitrary.  This means that we
are no longer limited to have space for the whole message in memory, i.e.
we can handle messages of any size.
.PP
This is useful when calculating checksum for files:
.PP
.Vb 1
\&    use Digest::MD4;
\&
\&    my $file = shift || "/etc/passwd";
\&    open(FILE, $file) or die "Can\*(Aqt open \*(Aq$file\*(Aq: $!";
\&    binmode(FILE);
\&
\&    $md4 = Digest::MD4\->new;
\&    while (<FILE>) {
\&        $md4\->add($_);
\&    }
\&    close(FILE);
\&    print $md4\->b64digest, " $file\en";
.Ve
.PP
Or we can use the addfile method for more efficient reading of
the file:
.PP
.Vb 1
\&    use Digest::MD4;
\&
\&    my $file = shift || "/etc/passwd";
\&    open(FILE, $file) or die "Can\*(Aqt open \*(Aq$file\*(Aq: $!";
\&    binmode(FILE);
\&
\&    print Digest::MD4\->new\->addfile(*FILE)\->hexdigest, " $file\en";
.Ve
.PP
Perl 5.8 support Unicode characters in strings.  Since the \s-1MD4\s0
algorithm is only defined for strings of bytes, it can not be used on
strings that contains chars with ordinal number above 255.  The \s-1MD4\s0
functions and methods will croak if you try to feed them such input
data:
.PP
.Vb 1
\&    use Digest::MD4 qw(md4_hex);
\&
\&    my $str = "abc\ex{300}";
\&    print md4_hex($str), "\en";  # croaks
\&    # Wide character in subroutine entry
.Ve
.PP
What you can do is calculate the \s-1MD4\s0 checksum of the \s-1UTF\-8\s0
representation of such strings.  This is achieved by filtering the
string through \fBencode_utf8()\fR function:
.PP
.Vb 2
\&    use Digest::MD4 qw(md4_hex);
\&    use Encode qw(encode_utf8);
\&
\&    my $str = "abc\ex{300}";
\&    print md4_hex(encode_utf8($str)), "\en";
\&    # fc2ef2836f9bc3f44ed6d7adee2f1533
.Ve
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Digest,
Digest::MD2,
Digest::SHA1,
Digest::HMAC
.PP
\&\fBmd4sum\fR\|(1)
.PP
\&\s-1RFC 1320\s0
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
This library is free software; you can redistribute it and/or
modify it under the same terms as Perl itself.
.PP
.Vb 3
\& Copyright 1998\-2003 Gisle Aas.
\& Copyright 1995\-1996 Neil Winton.
\& Copyright 1991\-1992 RSA Data Security, Inc.
.Ve
.PP
The \s-1MD4\s0 algorithm is defined in \s-1RFC 1320.\s0 This implementation is
derived from the reference C code in \s-1RFC 1320\s0 which is covered by
the following copyright statement:
.IP "\(bu" 4

.Sp
.Vb 1
\&   Copyright (C) 1990\-2, RSA Data Security, Inc. All rights reserved.
\&
\&   License to copy and use this software is granted provided that it
\&   is identified as the "RSA Data Security, Inc. MD4 Message\-Digest
\&   Algorithm" in all material mentioning or referencing this software
\&   or this function.
\&
\&   License is also granted to make and use derivative works provided
\&   that such works are identified as "derived from the RSA Data
\&   Security, Inc. MD4 Message\-Digest Algorithm" in all material
\&   mentioning or referencing the derived work.
\&
\&   RSA Data Security, Inc. makes no representations concerning either
\&   the merchantability of this software or the suitability of this
\&   software for any particular purpose. It is provided "as is"
\&   without express or implied warranty of any kind.
\&
\&   These notices must be retained in any copies of any part of this
\&   documentation and/or software.
.Ve
.PP
This copyright does not prohibit distribution of any version of Perl
containing this extension under the terms of the \s-1GNU\s0 or Artistic
licenses.
.SH "AUTHORS"
.IX Header "AUTHORS"
The original \f(CW\*(C`MD5\*(C'\fR interface was written by Neil Winton
(\f(CW\*(C`N.Winton@axion.bt.co.uk\*(C'\fR).
.PP
The \f(CW\*(C`Digest::MD5\*(C'\fR module is written by Gisle Aas <gisle@ActiveState.com>.
.PP
The \f(CW\*(C`Digest::MD4\*(C'\fR module is derived from Digest::MD5 by Mike McCauley (mikem@airspayce.com)