[OpenSPARC-T2-SAM] / sam-t2 / devtools / v8plus / man / man3 / Digest.3

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.\" ========================================================================
.\"
.IX Title "Digest 3"
.TH Digest 3 "2001-09-21" "perl v5.8.8" "Perl Programmers Reference Guide"
.SH "NAME"
Digest \- Modules that calculate message digests
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 5
\&  $md5  = Digest->new("MD5");
\&  $sha1 = Digest->new("SHA-1");
\&  $sha256 = Digest->new("SHA-256");
\&  $sha384 = Digest->new("SHA-384");
\&  $sha512 = Digest->new("SHA-512");
.Ve
.PP
.Vb 1
\&  $hmac = Digest->HMAC_MD5($key);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The \f(CW\*(C`Digest::\*(C'\fR modules calculate digests, also called \*(L"fingerprints\*(R"
or \*(L"hashes\*(R", of some data, called a message.  The digest is (usually)
some small/fixed size string.  The actual size of the digest depend of
the algorithm used.  The message is simply a sequence of arbitrary
bytes or bits.
.PP
An important property of the digest algorithms is that the digest is
\&\fIlikely\fR to change if the message change in some way.  Another
property is that digest functions are one-way functions, that is it
should be \fIhard\fR to find a message that correspond to some given
digest.  Algorithms differ in how \*(L"likely\*(R" and how \*(L"hard\*(R", as well as
how efficient they are to compute.
.PP
Note that the properties of the algorithms change over time, as the
algorithms are analyzed and machines grow faster.  If your application
for instance depends on it being \*(L"impossible\*(R" to generate the same
digest for a different message it is wise to make it easy to plug in
stronger algorithms as the one used grow weaker.  Using the interface
documented here should make it easy to change algorithms later.
.PP
All \f(CW\*(C`Digest::\*(C'\fR modules provide the same programming interface.  A
functional interface for simple use, as well as an object oriented
interface that can handle messages of arbitrary length and which can
read files directly.
.PP
The digest can be delivered in three formats:
.IP "\fIbinary\fR" 8
.IX Item "binary"
This is the most compact form, but it is not well suited for printing
or embedding in places that can't handle arbitrary data.
.IP "\fIhex\fR" 8
.IX Item "hex"
A twice as long string of lowercase hexadecimal digits.
.IP "\fIbase64\fR" 8
.IX Item "base64"
A string of portable printable characters.  This is the base64 encoded
representation of the digest with any trailing padding removed.  The
string will be about 30% longer than the binary version.
MIME::Base64 tells you more about this encoding.
.PP
The functional interface is simply importable functions with the same
name as the algorithm.  The functions take the message as argument and
return the digest.  Example:
.PP
.Vb 2
\&  use Digest::MD5 qw(md5);
\&  $digest = md5($message);
.Ve
.PP
There are also versions of the functions with \*(L"_hex\*(R" or \*(L"_base64\*(R"
appended to the name, which returns the digest in the indicated form.
.SH "OO INTERFACE"
.IX Header "OO INTERFACE"
The following methods are available for all \f(CW\*(C`Digest::\*(C'\fR modules:
.IP "$ctx = Digest\->\s-1XXX\s0($arg,...)" 4
.IX Item "$ctx = Digest->XXX($arg,...)"
.PD 0
.ie n .IP "$ctx = Digest\->new(\s-1XXX\s0 => $arg,...)" 4
.el .IP "$ctx = Digest\->new(\s-1XXX\s0 => \f(CW$arg\fR,...)" 4
.IX Item "$ctx = Digest->new(XXX => $arg,...)"
.IP "$ctx = Digest::XXX\->new($arg,...)" 4
.IX Item "$ctx = Digest::XXX->new($arg,...)"
.PD
The constructor returns some object that encapsulate the state of the
message-digest algorithm.  You can add data to the object and finally
ask for the digest.  The \*(L"\s-1XXX\s0\*(R" should of course be replaced by the proper
name of the digest algorithm you want to use.
.Sp
The two first forms are simply syntactic sugar which automatically
load the right module on first use.  The second form allow you to use
algorithm names which contains letters which are not legal perl
identifiers, e.g. \*(L"\s-1SHA\-1\s0\*(R".  If no implementation for the given algorithm
can be found, then an exception is raised.
.Sp
If \fInew()\fR is called as an instance method (i.e. \f(CW$ctx\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, and the return value is the
reference to the object (i.e. \f(CW$ctx\fR).
.ie n .IP "$other_ctx = $ctx\->clone" 4
.el .IP "$other_ctx = \f(CW$ctx\fR\->clone" 4
.IX Item "$other_ctx = $ctx->clone"
The clone method creates a copy of the digest state object and returns
a reference to the copy.
.IP "$ctx\->reset" 4
.IX Item "$ctx->reset"
This is just an alias for \f(CW$ctx\fR\->new.
.ie n .IP "$ctx\->add( $data, ... )" 4
.el .IP "$ctx\->add( \f(CW$data\fR, ... )" 4
.IX Item "$ctx->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$ctx\fR object itself.
.ie n .IP "$ctx\->addfile( $io_handle )" 4
.el .IP "$ctx\->addfile( \f(CW$io_handle\fR )" 4
.IX Item "$ctx->addfile( $io_handle )"
The \f(CW$io_handle\fR is read until \s-1EOF\s0 and the content is appended to the
message we calculate the digest for.  The return value is the \f(CW$ctx\fR
object itself.
.ie n .IP "$ctx\->add_bits( $data\fR, \f(CW$nbits )" 4
.el .IP "$ctx\->add_bits( \f(CW$data\fR, \f(CW$nbits\fR )" 4
.IX Item "$ctx->add_bits( $data, $nbits )"
.PD 0
.ie n .IP "$ctx\->add_bits( $bitstring )" 4
.el .IP "$ctx\->add_bits( \f(CW$bitstring\fR )" 4
.IX Item "$ctx->add_bits( $bitstring )"
.PD
The bits provided are appended to the message we calculate the digest
for.  The return value is the \f(CW$ctx\fR object itself.
.Sp
The two argument form of \fIadd_bits()\fR will add the first \f(CW$nbits\fR bits
from data.  For the last potentially partial byte only the high order
\&\f(CW\*(C`$nbits % 8\*(C'\fR bits are used.  If \f(CW$nbits\fR is greater than \f(CW\*(C`length($data) * 8\*(C'\fR, then this method would do the same as \f(CW\*(C`$ctx\->add($data)\*(C'\fR, that is \f(CW$nbits\fR is silently ignored.
.Sp
The one argument form of \fIadd_bits()\fR takes a \f(CW$bitstring\fR of \*(L"1\*(R" and \*(L"0\*(R"
chars as argument.  It's a shorthand for \f(CW\*(C`$ctx\->add_bits(pack("B*",
$bitstring), length($bitstring))\*(C'\fR.
.Sp
This example shows two calls that should have the same effect:
.Sp
.Vb 2
\&   $ctx->add_bits("111100001010");
\&   $ctx->add_bits("\exF0\exA0", 12);
.Ve
.Sp
Most digest algorithms are byte based.  For those it is not possible
to add bits that are not a multiple of 8, and the \fIadd_bits()\fR method
will croak if you try.
.IP "$ctx\->digest" 4
.IX Item "$ctx->digest"
Return the binary digest for the message.
.Sp
Note that the \f(CW\*(C`digest\*(C'\fR operation is effectively a destructive,
read-once operation. Once it has been performed, the \f(CW$ctx\fR object is
automatically \f(CW\*(C`reset\*(C'\fR and can be used to calculate another digest
value.  Call \f(CW$ctx\fR\->clone\->digest if you want to calculate the digest
without reseting the digest state.
.IP "$ctx\->hexdigest" 4
.IX Item "$ctx->hexdigest"
Same as \f(CW$ctx\fR\->digest, but will return the digest in hexadecimal form.
.IP "$ctx\->b64digest" 4
.IX Item "$ctx->b64digest"
Same as \f(CW$ctx\fR\->digest, but will return the digest as a base64 encoded
string.
.SH "Digest speed"
.IX Header "Digest speed"
This table should give some indication on the relative speed of
different algorithms.  It is sorted by throughput based on a benchmark
done with of some implementations of this \s-1API:\s0
.PP
.Vb 1
\& Algorithm      Size    Implementation                  MB/s
.Ve
.PP
.Vb 13
\& MD4            128     Digest::MD4 v1.3               165.0
\& MD5            128     Digest::MD5 v2.33               98.8
\& SHA-256        256     Digest::SHA2 v1.1.0             66.7
\& SHA-1          160     Digest::SHA v4.3.1              58.9
\& SHA-1          160     Digest::SHA1 v2.10              48.8
\& SHA-256        256     Digest::SHA v4.3.1              41.3
\& Haval-256      256     Digest::Haval256 v1.0.4         39.8
\& SHA-384        384     Digest::SHA2 v1.1.0             19.6
\& SHA-512        512     Digest::SHA2 v1.1.0             19.3
\& SHA-384        384     Digest::SHA v4.3.1              19.2
\& SHA-512        512     Digest::SHA v4.3.1              19.2
\& Whirlpool      512     Digest::Whirlpool v1.0.2        13.0
\& MD2            128     Digest::MD2 v2.03                9.5
.Ve
.PP
.Vb 5
\& Adler-32        32     Digest::Adler32 v0.03            1.3
\& CRC-16          16     Digest::CRC v0.05                1.1
\& CRC-32          32     Digest::CRC v0.05                1.1
\& MD5            128     Digest::Perl::MD5 v1.5           1.0
\& CRC-CCITT       16     Digest::CRC v0.05                0.8
.Ve
.PP
These numbers was achieved Apr 2004 with ActivePerl\-5.8.3 running
under Linux on a P4 2.8 GHz \s-1CPU\s0.  The last 5 entries differ by being
pure perl implementations of the algorithms, which explains why they
are so slow.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Digest::Adler32, Digest::CRC, Digest::Haval256,
Digest::HMAC, Digest::MD2, Digest::MD4, Digest::MD5,
Digest::SHA, Digest::SHA1, Digest::SHA2, Digest::Whirlpool
.PP
New digest implementations should consider subclassing from Digest::base.
.PP
MIME::Base64
.SH "AUTHOR"
.IX Header "AUTHOR"
Gisle Aas <gisle@aas.no>
.PP
The \f(CW\*(C`Digest::\*(C'\fR interface is based on the interface originally
developed by Neil Winton for his \f(CW\*(C`MD5\*(C'\fR module.
.PP
This library is free software; you can redistribute it and/or
modify it under the same terms as Perl itself.
.PP
.Vb 2
\&    Copyright 1998-2001,2003-2004 Gisle Aas.
\&    Copyright 1995-1996 Neil Winton.
.Ve
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129	.\" ========================================================================
130	.\"
131	.IX Title "Digest 3"
132	.TH Digest 3 "2001-09-21" "perl v5.8.8" "Perl Programmers Reference Guide"
133	.SH "NAME"
134	Digest \- Modules that calculate message digests
135	.SH "SYNOPSIS"
136	.IX Header "SYNOPSIS"
137	.Vb 5
138	\& $md5 = Digest->new("MD5");
139	\& $sha1 = Digest->new("SHA-1");
140	\& $sha256 = Digest->new("SHA-256");
141	\& $sha384 = Digest->new("SHA-384");
142	\& $sha512 = Digest->new("SHA-512");
143	.Ve
144	.PP
145	.Vb 1
146	\& $hmac = Digest->HMAC_MD5($key);
147	.Ve
148	.SH "DESCRIPTION"
149	.IX Header "DESCRIPTION"
150	The \f(CW\(C`Digest::\(C'\fR modules calculate digests, also called \(L"fingerprints\(R"
151	or \(L"hashes\(R", of some data, called a message. The digest is (usually)
152	some small/fixed size string. The actual size of the digest depend of
153	the algorithm used. The message is simply a sequence of arbitrary
154	bytes or bits.
155	.PP
156	An important property of the digest algorithms is that the digest is
157	\&\fIlikely\fR to change if the message change in some way. Another
158	property is that digest functions are one-way functions, that is it
159	should be \fIhard\fR to find a message that correspond to some given
160	digest. Algorithms differ in how \(L"likely\(R" and how \(L"hard\(R", as well as
161	how efficient they are to compute.
162	.PP
163	Note that the properties of the algorithms change over time, as the
164	algorithms are analyzed and machines grow faster. If your application
165	for instance depends on it being \(L"impossible\(R" to generate the same
166	digest for a different message it is wise to make it easy to plug in
167	stronger algorithms as the one used grow weaker. Using the interface
168	documented here should make it easy to change algorithms later.
169	.PP
170	All \f(CW\(C`Digest::\(C'\fR modules provide the same programming interface. A
171	functional interface for simple use, as well as an object oriented
172	interface that can handle messages of arbitrary length and which can
173	read files directly.
174	.PP
175	The digest can be delivered in three formats:
176	.IP "\fIbinary\fR" 8
177	.IX Item "binary"
178	This is the most compact form, but it is not well suited for printing
179	or embedding in places that can't handle arbitrary data.
180	.IP "\fIhex\fR" 8
181	.IX Item "hex"
182	A twice as long string of lowercase hexadecimal digits.
183	.IP "\fIbase64\fR" 8
184	.IX Item "base64"
185	A string of portable printable characters. This is the base64 encoded
186	representation of the digest with any trailing padding removed. The
187	string will be about 30% longer than the binary version.
188	MIME::Base64 tells you more about this encoding.
189	.PP
190	The functional interface is simply importable functions with the same
191	name as the algorithm. The functions take the message as argument and
192	return the digest. Example:
193	.PP
194	.Vb 2
195	\& use Digest::MD5 qw(md5);
196	\& $digest = md5($message);
197	.Ve
198	.PP
199	There are also versions of the functions with \(L"_hex\(R" or \(L"_base64\(R"
200	appended to the name, which returns the digest in the indicated form.
201	.SH "OO INTERFACE"
202	.IX Header "OO INTERFACE"
203	The following methods are available for all \f(CW\(C`Digest::\(C'\fR modules:
204	.IP "$ctx = Digest\->\s-1XXX\s0($arg,...)" 4
205	.IX Item "$ctx = Digest->XXX($arg,...)"
206	.PD 0
207	.ie n .IP "$ctx = Digest\->new(\s-1XXX\s0 => $arg,...)" 4
208	.el .IP "$ctx = Digest\->new(\s-1XXX\s0 => \f(CW$arg\fR,...)" 4
209	.IX Item "$ctx = Digest->new(XXX => $arg,...)"
210	.IP "$ctx = Digest::XXX\->new($arg,...)" 4
211	.IX Item "$ctx = Digest::XXX->new($arg,...)"
212	.PD
213	The constructor returns some object that encapsulate the state of the
214	message-digest algorithm. You can add data to the object and finally
215	ask for the digest. The \(L"\s-1XXX\s0\(R" should of course be replaced by the proper
216	name of the digest algorithm you want to use.
217	.Sp
218	The two first forms are simply syntactic sugar which automatically
219	load the right module on first use. The second form allow you to use
220	algorithm names which contains letters which are not legal perl
221	identifiers, e.g. \(L"\s-1SHA\-1\s0\(R". If no implementation for the given algorithm
222	can be found, then an exception is raised.
223	.Sp
224	If \fInew()\fR is called as an instance method (i.e. \f(CW$ctx\fR\->new) it will just
225	reset the state the object to the state of a newly created object. No
226	new object is created in this case, and the return value is the
227	reference to the object (i.e. \f(CW$ctx\fR).
228	.ie n .IP "$other_ctx = $ctx\->clone" 4
229	.el .IP "$other_ctx = \f(CW$ctx\fR\->clone" 4
230	.IX Item "$other_ctx = $ctx->clone"
231	The clone method creates a copy of the digest state object and returns
232	a reference to the copy.
233	.IP "$ctx\->reset" 4
234	.IX Item "$ctx->reset"
235	This is just an alias for \f(CW$ctx\fR\->new.
236	.ie n .IP "$ctx\->add( $data, ... )" 4
237	.el .IP "$ctx\->add( \f(CW$data\fR, ... )" 4
238	.IX Item "$ctx->add( $data, ... )"
239	The \f(CW$data\fR provided as argument are appended to the message we
240	calculate the digest for. The return value is the \f(CW$ctx\fR object itself.
241	.ie n .IP "$ctx\->addfile( $io_handle )" 4
242	.el .IP "$ctx\->addfile( \f(CW$io_handle\fR )" 4
243	.IX Item "$ctx->addfile( $io_handle )"
244	The \f(CW$io_handle\fR is read until \s-1EOF\s0 and the content is appended to the
245	message we calculate the digest for. The return value is the \f(CW$ctx\fR
246	object itself.
247	.ie n .IP "$ctx\->add_bits( $data\fR, \f(CW$nbits )" 4
248	.el .IP "$ctx\->add_bits( \f(CW$data\fR, \f(CW$nbits\fR )" 4
249	.IX Item "$ctx->add_bits( $data, $nbits )"
250	.PD 0
251	.ie n .IP "$ctx\->add_bits( $bitstring )" 4
252	.el .IP "$ctx\->add_bits( \f(CW$bitstring\fR )" 4
253	.IX Item "$ctx->add_bits( $bitstring )"
254	.PD
255	The bits provided are appended to the message we calculate the digest
256	for. The return value is the \f(CW$ctx\fR object itself.
257	.Sp
258	The two argument form of \fIadd_bits()\fR will add the first \f(CW$nbits\fR bits
259	from data. For the last potentially partial byte only the high order
260	\&\f(CW\(C`$nbits % 8\(C'\fR bits are used. If \f(CW$nbits\fR is greater than \f(CW\(C`length($data) 8\(C'\fR, then this method would do the same as \f(CW\(C`$ctx\->add($data)\*(C'\fR, that is \f(CW$nbits\fR is silently ignored.
261	.Sp
262	The one argument form of \fIadd_bits()\fR takes a \f(CW$bitstring\fR of \(L"1\(R" and \(L"0\(R"
263	chars as argument. It's a shorthand for \f(CW\(C`$ctx\->add_bits(pack("B",
264	$bitstring), length($bitstring))\*(C'\fR.
265	.Sp
266	This example shows two calls that should have the same effect:
267	.Sp
268	.Vb 2
269	\& $ctx->add_bits("111100001010");
270	\& $ctx->add_bits("\exF0\exA0", 12);
271	.Ve
272	.Sp
273	Most digest algorithms are byte based. For those it is not possible
274	to add bits that are not a multiple of 8, and the \fIadd_bits()\fR method
275	will croak if you try.
276	.IP "$ctx\->digest" 4
277	.IX Item "$ctx->digest"
278	Return the binary digest for the message.
279	.Sp
280	Note that the \f(CW\(C`digest\(C'\fR operation is effectively a destructive,
281	read-once operation. Once it has been performed, the \f(CW$ctx\fR object is
282	automatically \f(CW\(C`reset\(C'\fR and can be used to calculate another digest
283	value. Call \f(CW$ctx\fR\->clone\->digest if you want to calculate the digest
284	without reseting the digest state.
285	.IP "$ctx\->hexdigest" 4
286	.IX Item "$ctx->hexdigest"
287	Same as \f(CW$ctx\fR\->digest, but will return the digest in hexadecimal form.
288	.IP "$ctx\->b64digest" 4
289	.IX Item "$ctx->b64digest"
290	Same as \f(CW$ctx\fR\->digest, but will return the digest as a base64 encoded
291	string.
292	.SH "Digest speed"
293	.IX Header "Digest speed"
294	This table should give some indication on the relative speed of
295	different algorithms. It is sorted by throughput based on a benchmark
296	done with of some implementations of this \s-1API:\s0
297	.PP
298	.Vb 1
299	\& Algorithm Size Implementation MB/s
300	.Ve
301	.PP
302	.Vb 13
303	\& MD4 128 Digest::MD4 v1.3 165.0
304	\& MD5 128 Digest::MD5 v2.33 98.8
305	\& SHA-256 256 Digest::SHA2 v1.1.0 66.7
306	\& SHA-1 160 Digest::SHA v4.3.1 58.9
307	\& SHA-1 160 Digest::SHA1 v2.10 48.8
308	\& SHA-256 256 Digest::SHA v4.3.1 41.3
309	\& Haval-256 256 Digest::Haval256 v1.0.4 39.8
310	\& SHA-384 384 Digest::SHA2 v1.1.0 19.6
311	\& SHA-512 512 Digest::SHA2 v1.1.0 19.3
312	\& SHA-384 384 Digest::SHA v4.3.1 19.2
313	\& SHA-512 512 Digest::SHA v4.3.1 19.2
314	\& Whirlpool 512 Digest::Whirlpool v1.0.2 13.0
315	\& MD2 128 Digest::MD2 v2.03 9.5
316	.Ve
317	.PP
318	.Vb 5
319	\& Adler-32 32 Digest::Adler32 v0.03 1.3
320	\& CRC-16 16 Digest::CRC v0.05 1.1
321	\& CRC-32 32 Digest::CRC v0.05 1.1
322	\& MD5 128 Digest::Perl::MD5 v1.5 1.0
323	\& CRC-CCITT 16 Digest::CRC v0.05 0.8
324	.Ve
325	.PP
326	These numbers was achieved Apr 2004 with ActivePerl\-5.8.3 running
327	under Linux on a P4 2.8 GHz \s-1CPU\s0. The last 5 entries differ by being
328	pure perl implementations of the algorithms, which explains why they
329	are so slow.
330	.SH "SEE ALSO"
331	.IX Header "SEE ALSO"
332	Digest::Adler32, Digest::CRC, Digest::Haval256,
333	Digest::HMAC, Digest::MD2, Digest::MD4, Digest::MD5,
334	Digest::SHA, Digest::SHA1, Digest::SHA2, Digest::Whirlpool
335	.PP
336	New digest implementations should consider subclassing from Digest::base.
337	.PP
338	MIME::Base64
339	.SH "AUTHOR"
340	.IX Header "AUTHOR"
341	Gisle Aas <gisle@aas.no>
342	.PP
343	The \f(CW\(C`Digest::\(C'\fR interface is based on the interface originally
344	developed by Neil Winton for his \f(CW\(C`MD5\(C'\fR module.
345	.PP
346	This library is free software; you can redistribute it and/or
347	modify it under the same terms as Perl itself.
348	.PP
349	.Vb 2
350	\& Copyright 1998-2001,2003-2004 Gisle Aas.
351	\& Copyright 1995-1996 Neil Winton.
352	.Ve