1 |
=head1 NAME |
2 |
|
3 |
Crypt::Spritz - Spritz stream cipher/hash/MAC/AEAD/CSPRNG family |
4 |
|
5 |
=head1 SYNOPSIS |
6 |
|
7 |
use Crypt::Spritz; |
8 |
|
9 |
# see the commented examples in their respective classes, |
10 |
# but basically |
11 |
|
12 |
my $cipher = new Crypt::Spritz::Cipher::XOR $key, $iv; |
13 |
$ciphertext = $cipher->crypt ($cleartext); |
14 |
|
15 |
my $hasher = new Crypt::Spritz::Hash; |
16 |
$hasher->add ($data); |
17 |
$digest = $hasher->finish; |
18 |
|
19 |
my $hasher = new Crypt::Spritz::MAC $key; |
20 |
$hasher->add ($data); |
21 |
$mac = $hasher->finish; |
22 |
|
23 |
my $aead = new Crypt::Spritz::AEAD::XOR $key; |
24 |
$aead->nonce ($counter); |
25 |
$aead->associated_data ($header); |
26 |
$ciphertext = $aead->crypt ($cleartext); |
27 |
$mac = $aead->mac; |
28 |
|
29 |
my $prng = new Crypt::Spritz::PRNG $entropy; |
30 |
$prng->add ($additional_entropy); |
31 |
$keydata = $prng->get (32); |
32 |
|
33 |
=head1 DESCRIPTION |
34 |
|
35 |
This module implements the Spritz spongelike function (with N=256), the |
36 |
spiritual successor of RC4 developed by Ron Rivest and Jacob Schuldt. |
37 |
|
38 |
Its strength is extreme versatility (you get a stream cipher, a hash, a |
39 |
MAC, a DRBG/CSPRNG, an authenticated encryption block/stream cipher and |
40 |
more) and extremely simple and small code (encryption and authentication |
41 |
can be had in 1KB of compiled code on amd64, which isn't an issue for most |
42 |
uses in Perl, but is useful in embedded situations, or e.g. when doing |
43 |
crypto using javascript in a browser and communicating with Perl). |
44 |
|
45 |
Its weakness is its relatively slow speed (encryption is a few times |
46 |
slower than RC4 or AES, hashing many times slower than SHA-3, although |
47 |
this might be reversed on an 8-bit-cpu) and the fact that it is totally |
48 |
unproven in the field (as of this writing, the cipher was just a few |
49 |
months old), so it can't be called production-ready. |
50 |
|
51 |
All the usual caveats regarding stream ciphers apply - never repeat your |
52 |
key, never repeat your nonce and so on - you should have some basic |
53 |
understanding of cryptography before using this cipher in your own |
54 |
designs. |
55 |
|
56 |
The Spritz base class is not meant for end users. To make usage simpler |
57 |
and safer, a number of convenience classes are provided for typical |
58 |
end-user tasks: |
59 |
|
60 |
encryption - Crypt::Spritz::Cipher::XOR |
61 |
hashing - Crypt::Spritz::Hash |
62 |
message authentication - Crypt::Spritz::MAC |
63 |
authenticated encryption - Crypt::Spritz::AEAD::XOR |
64 |
random number generation - Crypt::Spritz::PRNG |
65 |
|
66 |
=cut |
67 |
|
68 |
package Crypt::Spritz; |
69 |
|
70 |
use XSLoader; |
71 |
|
72 |
$VERSION = '0.1'; |
73 |
|
74 |
XSLoader::load __PACKAGE__, $VERSION; |
75 |
|
76 |
@Crypt::Spritz::ISA = Crypt::Spritz::Base::; |
77 |
|
78 |
@Crypt::Spritz::Hash::ISA = |
79 |
@Crypt::Spritz::PRNG::ISA = |
80 |
@Crypt::Spritz::Cipher::ISA = |
81 |
@Crypt::Spritz::AEAD::ISA = Crypt::Spritz::Base::; |
82 |
|
83 |
@Crypt::Spritz::MAC::ISA = Crypt::Spritz::Hash::; |
84 |
|
85 |
@Crypt::Spritz::Cipher::XOR::ISA = Crypt::Spritz::Cipher::; |
86 |
@Crypt::Spritz::AEAD::XOR::ISA = Crypt::Spritz::AEAD::; |
87 |
|
88 |
sub Crypt::Spritz::Cipher::keysize () { 32 } |
89 |
sub Crypt::Spritz::Cipher::blocksize () { 64 } |
90 |
|
91 |
*Crypt::Spritz::Hash::new = \&Crypt::Spritz::new; |
92 |
|
93 |
*Crypt::Spritz::Hash::add = |
94 |
*Crypt::Spritz::PRNG::add = \&Crypt::Spritz::absorb; |
95 |
|
96 |
*Crypt::Spritz::PRNG::get = \&Crypt::Spritz::squeeze; |
97 |
|
98 |
*Crypt::Spritz::AEAD::new = \&Crypt::Spritz::MAC::new; |
99 |
*Crypt::Spritz::AEAD::finish = \&Crypt::Spritz::Hash::finish; |
100 |
|
101 |
*Crypt::Spritz::AEAD::associated_data = |
102 |
*Crypt::Spritz::AEAD::nonce = \&Crypt::Spritz::absorb_and_stop; |
103 |
|
104 |
|
105 |
=head2 THE Crypt::Spritz CLASS |
106 |
|
107 |
This class implements most of the Spritz primitives. To use it effectively |
108 |
you should understand them, for example, by reading the L<Spritz |
109 |
paper/http://people.csail.mit.edu/rivest/pubs/RS14.pdf>, especially |
110 |
pp. 5-6. |
111 |
|
112 |
The Spritz primitive corresponding to the Perl method is given as |
113 |
comment. |
114 |
|
115 |
=over 4 |
116 |
|
117 |
=item $spritz = new Crypt::Spritz # InitializeState |
118 |
|
119 |
Creates and returns a new, initialised Spritz state. |
120 |
|
121 |
=item $spritz->init # InitializeState |
122 |
|
123 |
Initialises the Spritz state again, throwing away the previous state. |
124 |
|
125 |
=item $another_spritz = $spritz->clone |
126 |
|
127 |
Make an exact copy of the spritz state. This method can be called on all |
128 |
of the objects in this module, but is documented separately to give some |
129 |
cool usage examples. |
130 |
|
131 |
=item $spritz->update # Update |
132 |
|
133 |
=item $spritz->whip ($r) # Whip |
134 |
|
135 |
=item $spritz->crush # Crush |
136 |
|
137 |
=item $spritz->shuffle # Shuffle |
138 |
|
139 |
=item $spritz->output # Output |
140 |
|
141 |
Calls the Spritz primitive ovf the same name - these are not normally |
142 |
called manually. |
143 |
|
144 |
=item $spritz->absorb ($I) # Absorb |
145 |
|
146 |
Absorbs the given data into the state (usually used for key material, |
147 |
nonces, IVs messages to be hashed and so on). |
148 |
|
149 |
=item $spritz->absorb_stop # AbsorbStop |
150 |
|
151 |
Absorbs a special stop symbol - this is usually used as delimiter between |
152 |
multiple strings to be absorbed, to thwart extension attacks. |
153 |
|
154 |
=item $spritz->absorb_and_stop ($I) |
155 |
|
156 |
This is a convenience function that simply calls C<absorb> followed by |
157 |
C<absorb_stop>. |
158 |
|
159 |
=item $octet = $spritz->drip # Drip |
160 |
|
161 |
Squeezes out a single byte from the state. |
162 |
|
163 |
=item $octets = $spritz->squeeze ($len) # Squeeze |
164 |
|
165 |
Squeezes out the requested number of bytes from the state - this is usually |
166 |
|
167 |
=back |
168 |
|
169 |
|
170 |
=head2 THE Crypt::Spritz::Cipher::XOR CLASS |
171 |
|
172 |
This class implements stream encryption/decryption. It doesn't implement |
173 |
the standard Spritz encryption but the XOR variant (called B<spritz-xor> |
174 |
in the paper). |
175 |
|
176 |
The XOR variant should be as secure as the standard variant, but |
177 |
doesn't have separate encryption and decryaption functions, which saves |
178 |
codesize. IT is not compatible with standard Spritz encryption, however - |
179 |
drop me a note if you want that implemented as well. |
180 |
|
181 |
Typical use for encryption I<and> decryption (code is identical for |
182 |
decryption, you simply pass the encrypted data to C<crypt>): |
183 |
|
184 |
# create a cipher - $salt can be a random string you send |
185 |
# with your message, in clear, a counter (best), or empty if |
186 |
# you only want to encrypt one message with the given key. |
187 |
# 16 or 32 octets are typical sizes for the key, for the salt, |
188 |
# use whatever you need to give a unique salt for every |
189 |
# message you encrypt with the same key. |
190 |
|
191 |
my $cipher = Crypt::Spritz::Cipher::XOR $key, $salt; |
192 |
|
193 |
# encrypt a message in one or more calls to crypt |
194 |
|
195 |
my $encrypted; |
196 |
|
197 |
$encrypted .= $cipher->crypt ("This is"); |
198 |
$encrypted .= $cipher->crypt ("all very"); |
199 |
$encrypted .= $cipher->crypt ("secret"); |
200 |
|
201 |
# that's all |
202 |
|
203 |
=over 4 |
204 |
|
205 |
=item $cipher = new Crypt::Spritz::Cipher::XOR $key[, $iv] |
206 |
|
207 |
Creates a new cipher object usable for encryption and decryption. The |
208 |
C<$key> must be provided, the initial vector C<$IV> is optional. |
209 |
|
210 |
Both C<$key> and C<$IV> can be of any length. Typical lengths for the |
211 |
C<$key> are 16 (128 bit) or 32 (256 bit), while the C<$IV> simply needs to |
212 |
be long enough to distinguish repeated uses of tghe same key. |
213 |
|
214 |
=item $encrypted = $cipher->crypt ($cleartext) |
215 |
|
216 |
=item $cleartext = $cipher->crypt ($encrypted) |
217 |
|
218 |
Encrypt or decrypt a piece of a message. This can be called as many times |
219 |
as you want, and the message can be split into as few or many pieces as |
220 |
required without affecting the results. |
221 |
|
222 |
=item $cipher->crypt_inplace ($cleartext_or_ciphertext) |
223 |
|
224 |
Same as C<crypt>, except it I<modifies the argument in-place>. |
225 |
|
226 |
=item $another_cipher = $cipher->clone |
227 |
|
228 |
Make an exact copy of the cipher state. This can be useful to cache states |
229 |
for reuse later, for example, to avoid expensive key setups. |
230 |
|
231 |
While there might be use cases for this feature, it makes a lot more sense |
232 |
for C<Crypt::Spritz::AEAD> and C<Crypt::Spritz::AEAD::XOR>, as they allow |
233 |
you to specify the IV/nonce separately. |
234 |
|
235 |
=item $constant_32 = $cipher->keysize |
236 |
|
237 |
=item $constant_64 = $cipher->blocksize |
238 |
|
239 |
These methods are provided for L<Crypt::CBC> compatibility and simply |
240 |
return C<32> and C<64>, respectively. |
241 |
|
242 |
Note that it is pointless to use Spritz with L<Crypt::CBC>, as Spritz is |
243 |
not a block cipher and already provides an appropriate mode. |
244 |
|
245 |
=back |
246 |
|
247 |
|
248 |
=head2 THE Crypt::Spritz::Hash CLASS |
249 |
|
250 |
This implements the Spritz digest/hash algorithm. It works very similar to |
251 |
other digest modules on CPAN, such as L<Digest::SHA3>. |
252 |
|
253 |
Typical use for hashing: |
254 |
|
255 |
# create hasher object |
256 |
my $hasher = new Crypt::Spritz::Hash; |
257 |
|
258 |
# now feed data to be hashed into $hasher |
259 |
# in as few or many calls as required |
260 |
$hasher->add ("Some data"); |
261 |
$hasher->add ("Some more"); |
262 |
|
263 |
# extract the hash - the object is not usable afterwards |
264 |
my $digest = $hasher->finish (32); |
265 |
|
266 |
=over 4 |
267 |
|
268 |
=item $hasher = new Crypt::Spritz::Hash |
269 |
|
270 |
Creates a new hasher object. |
271 |
|
272 |
=item $hasher->add ($data) |
273 |
|
274 |
Adds data to be hashed into the hasher state. It doesn't matter whether |
275 |
you pass your data in in one go or split it up, the hash will be the same. |
276 |
|
277 |
=item $digest = $hasher->finish ($length) |
278 |
|
279 |
Calculates a hash digest of the given length and return it. The object |
280 |
cannot sensibly be used for further hashing afterwards. |
281 |
|
282 |
Typical digest lengths are 16 and 32, corresponding to 128 and 256 bit |
283 |
digests, respectively. |
284 |
|
285 |
=item $another_hasher = $hasher->clone |
286 |
|
287 |
Make an exact copy of the hasher state. This can be useful to generate |
288 |
incremental hashes, for example. |
289 |
|
290 |
Example: generate a hash for the data already fed into the hasher, by keeping |
291 |
the original hasher for further C<add> calls and calling C<finish> on a C<clone>. |
292 |
|
293 |
my $intermediate_hash = $hasher->clone->finish; |
294 |
|
295 |
Example: hash 64KiB of data, and generate a hash after every kilobyte that |
296 |
is over the full data. |
297 |
|
298 |
my $hasher = new Crypt::Spritz::Hash; |
299 |
|
300 |
for (0..63) { |
301 |
my $kib = "x" x 1024; # whatever data |
302 |
|
303 |
$hasher->add ($kib); |
304 |
|
305 |
my $intermediate_hash = $hasher->clone->finish; |
306 |
... |
307 |
} |
308 |
|
309 |
These kind of intermediate hashes are sometimes used in communications |
310 |
protocols to protect the integrity of the data incrementally, e.g. to |
311 |
detect errors early, while still having a complete hash at the end of a |
312 |
transfer. |
313 |
|
314 |
=back |
315 |
|
316 |
|
317 |
=head2 THE Crypt::Spritz::MAC CLASS |
318 |
|
319 |
This implements the Spritz Message Authentication Code algorithm. It works |
320 |
very similar to other digest modules on CPAN, such as L<Digest::SHA3>, but |
321 |
implements an authenticated digest (like L<Digest::HMAC>). |
322 |
|
323 |
I<Authenticated> means that, unlike L<Crypt::Spritz::Hash>, where |
324 |
everybody can verify and recreate the hash value for some data, with a |
325 |
MAC, knowledge of the (hopefully) secret key is required both to create |
326 |
and to verify the digest. |
327 |
|
328 |
Typical use for hashing is almost the same as with L<Crypt::Spritz::MAC>, |
329 |
except a key (typically 16 or 32 octets) is provided to the constructor: |
330 |
|
331 |
# create hasher object |
332 |
my $hasher = new Crypt::Spritz::Mac $key; |
333 |
|
334 |
# now feed data to be hashed into $hasher |
335 |
# in as few or many calls as required |
336 |
$hasher->add ("Some data"); |
337 |
$hasher->add ("Some more"); |
338 |
|
339 |
# extract the mac - the object is not usable afterwards |
340 |
my $mac = $hasher->finish (32); |
341 |
|
342 |
=over 4 |
343 |
|
344 |
=item $hasher = new Crypt::Spritz::MAC $key |
345 |
|
346 |
Creates a new hasher object. The C<$key> can be of any length, but 16 and |
347 |
32 (128 and 256 bit) are customary. |
348 |
|
349 |
=item $hasher->add ($data) |
350 |
|
351 |
Adds data to be hashed into the hasher state. It doesn't matter whether |
352 |
you pass your data in in one go or split it up, the hash will be the same. |
353 |
|
354 |
=item $mac = $hasher->finish ($length) |
355 |
|
356 |
Calculates a message code of the given length and return it. The object |
357 |
cannot sensibly be used for further hashing afterwards. |
358 |
|
359 |
Typical digest lengths are 16 and 32, corresponding to 128 and 256 bit |
360 |
digests, respectively. |
361 |
|
362 |
=item $another_hasher = $hasher->clone |
363 |
|
364 |
Make an exact copy of the hasher state. This can be useful to |
365 |
generate incremental macs, for example. |
366 |
|
367 |
See the description for the C<Crypt::Spritz::Hash::clone> method for some |
368 |
examples. |
369 |
|
370 |
=back |
371 |
|
372 |
|
373 |
=head2 THE Crypt::Spritz::AEAD::XOR CLASS |
374 |
|
375 |
This is the most complicated class - it combines encryption and |
376 |
message authentication into a single "authenticated encryption |
377 |
mode". It is similar to using both L<Crypt::Spritz::Cipher::XOR> and |
378 |
L<Crypt::Spritz::MAC>, but makes it harder to make mistakes in combining |
379 |
them. |
380 |
|
381 |
You can additionally provide cleartext data that will not be encrypted or |
382 |
decrypted, but that is nevertheless authenticated using the MAC, which |
383 |
is why this mode is called I<AEAD>, I<Authenticated Encryption with |
384 |
Associated Data>. Associated data is usually used to any header data that |
385 |
is in cleartext, but should nevertheless be authenticated. |
386 |
|
387 |
This implementation implements the XOR variant. Just as with |
388 |
L<Crypt::Spritz::Cipher::XOR>, this means it is not compatible with |
389 |
the standard mode, but uses less code and doesn't distinguish between |
390 |
encryption and decryption. |
391 |
|
392 |
Typical usage is as follows: |
393 |
|
394 |
# create a new aead object |
395 |
# you use one object per message |
396 |
# key length customarily is 16 or 32 |
397 |
my $aead = new Crypt::Spritz::AEAD::XOR $key; |
398 |
|
399 |
# now you must feed the nonce. if you do not need a nonce, |
400 |
# you can provide the empty string, but you have to call it |
401 |
# after creating the object, before calling associated_data. |
402 |
# the nonce must be different for each usage of the $key. |
403 |
# a counter of some kind is good enough. |
404 |
# reusing a nonce with the same key completely |
405 |
# destroys security! |
406 |
$aead->nonce ($counter); |
407 |
|
408 |
# then you must feed any associated data you have. if you |
409 |
# do not have associated cleartext data, you can provide the empty |
410 |
# string, but you have to call it after nonce and before crypt. |
411 |
$aead->associated_data ($header); |
412 |
|
413 |
# next, you call crypt one or more times with your data |
414 |
# to be encrypted (opr decrypted). |
415 |
# all except the last call must use a length that is a |
416 |
# multiple of 64. |
417 |
# the last block can have any length. |
418 |
my $encrypted; |
419 |
|
420 |
$encrypted .= $aead->crypt ("1" x 64); |
421 |
$encrypted .= $aead->crypt ("2" x 64); |
422 |
$encrypted .= $aead->crypt ("3456"); |
423 |
|
424 |
# finally you can calculate the MAC for all of the above |
425 |
my $mac = $aead->finish; |
426 |
|
427 |
=over 4 |
428 |
|
429 |
=item $aead = new Crypt::Spritz::AEAD::XOR $key |
430 |
|
431 |
Creates a new cipher object usable for encryption and decryption. |
432 |
|
433 |
The C<$key> can be of any length. Typical lengths for the C<$key> are 16 |
434 |
(128 bit) or 32 (256 bit). |
435 |
|
436 |
After creation, you have to call C<nonce> next. |
437 |
|
438 |
=item $aead->nonce ($nonce) |
439 |
|
440 |
Provide the nonce value (nonce means "value used once"), a value the is |
441 |
unique between all uses with the same key. This method I<must> be called |
442 |
I<after> C<new> and I<before> C<associated_data>. |
443 |
|
444 |
If you only ever use a given key once, you can provide an empty nonce - |
445 |
but you still have to call the method. |
446 |
|
447 |
Common strategies to provide a nonce are to implement a persistent counter |
448 |
or to generate a random string of sufficient length to guarantee that it |
449 |
differs each time. |
450 |
|
451 |
The problem with counters is that you might get confused and forget |
452 |
increments, and thus reuse the same sequence number. The problem with |
453 |
random strings i that your random number generator might be hosed and |
454 |
generate the same randomness multiple times (randomness can be very hard |
455 |
to get especially on embedded devices). |
456 |
|
457 |
=item $aead->associated_data ($data) |
458 |
|
459 |
Provide the associated data (cleartext data to be authenticated but not |
460 |
encrypted). This method I<must> be called I<after> C<nonce> and I<before> |
461 |
C<crypt>. |
462 |
|
463 |
If you don't have any associated data, you can provide an empty string - |
464 |
but you still have to call the method. |
465 |
|
466 |
Associated data is typically header data - data anybody is allowed to |
467 |
see in cleartext, but that should nevertheless be protected with an |
468 |
authentication code. Typically such data is used to identify where to |
469 |
forward a message to, how to find the key to decrypt the message or in |
470 |
general how to interpret the encrypted part of a message. |
471 |
|
472 |
=item $encrypted = $cipher->crypt ($cleartext) |
473 |
|
474 |
=item $cleartext = $cipher->crypt ($encrypted) |
475 |
|
476 |
Encrypt or decrypt a piece of a message. This can be called as many times |
477 |
as you want, and the message can be split into as few or many pieces as |
478 |
required without affecting the results, with one exception: All except the |
479 |
last call to C<crypt> needs to pass in a multiple of C<64> octets. The |
480 |
last call to C<crypt> does not have this limitation. |
481 |
|
482 |
=item $cipher->crypt_inplace ($cleartext_or_ciphertext) |
483 |
|
484 |
Same as C<crypt>, except it I<modifies the argument in-place>. |
485 |
|
486 |
=item $another_cipher = $cipher->clone |
487 |
|
488 |
Make an exact copy of the cipher state. This can be useful to cache states |
489 |
for reuse later, for example, to avoid expensive key setups. |
490 |
|
491 |
Example: set up a cipher state with a key, then clone and use it to |
492 |
encrypt messages with different nonces. |
493 |
|
494 |
my $cipher = new Crypt::Spritz::AEAD::XOR $key; |
495 |
|
496 |
my $message_counter; |
497 |
|
498 |
for my $message ("a", "b", "c") { |
499 |
my $clone = $cipher->clone; |
500 |
$clone->nonce (pack "N", ++$message_counter); |
501 |
$clone->associated_data (""); |
502 |
my $encrypted = $clone->crypt ($message); |
503 |
... |
504 |
} |
505 |
|
506 |
=back |
507 |
|
508 |
|
509 |
=head2 THE Crypt::Spritz::PRNG CLASS |
510 |
|
511 |
This class implements a Pseudorandom Number Generatore (B<PRNG>), |
512 |
sometimes also called a Deterministic Random Bit Generator (B<DRBG>). In |
513 |
fact, it is even cryptographically secure, making it a B<CSPRNG>. |
514 |
|
515 |
Typical usage as a random number generator involves creating a PRNG |
516 |
object with a seed of your choice, and then fetching randomness via |
517 |
C<get>: |
518 |
|
519 |
# create a PRNG object, use a seed string of your choice |
520 |
my $prng = new Crypt::Spritz::PRNG $seed; |
521 |
|
522 |
# now call get as many times as you wish to get binary randomness |
523 |
my $some_randomness = $prng->get (17); |
524 |
my moree_randomness = $prng->get (5000); |
525 |
... |
526 |
|
527 |
Typical usage as a cryptographically secure random number generator is to |
528 |
feed in some secret entropy (32 octets/256 bits are commonly considered |
529 |
enough), for example from C</dev/random> or C</dev/urandom>, and then |
530 |
generate some key material. |
531 |
|
532 |
# create a PRNG object |
533 |
my $prng = new Crypt::Spritz::PRNG; |
534 |
|
535 |
# seed some entropy (either via ->add or in the constructor) |
536 |
$prng->add ($some_secret_highly_entropic_string); |
537 |
|
538 |
# now call get as many times as you wish to get |
539 |
# hard to guess binary randomness |
540 |
my $key1 = $prng->get (32); |
541 |
my $key2 = $prng->get (16); |
542 |
... |
543 |
|
544 |
# for long running programs, it is advisable to |
545 |
# reseed the PRNG from time to time with new entropy |
546 |
$prng->add ($some_more_entropy); |
547 |
|
548 |
=over 4 |
549 |
|
550 |
=item $prng = new Crypt::Spritz::PRNG [$seed] |
551 |
|
552 |
Creates a new random number generator object. If C<$seed> is given, then |
553 |
the C<$seed> is added to the internal state as if by a call to C<add>. |
554 |
|
555 |
=item $prng->add ($entropy) |
556 |
|
557 |
Adds entropy to the internal state, thereby hopefully making it harder |
558 |
to guess. Good sources for entropy are irregular hardware events, or |
559 |
randomness provided by C</dev/urandom> or C</dev/random>. |
560 |
|
561 |
The design of the Spritz PRNG should make it strong against attacks where |
562 |
the attacker controls all the entropy, so it should be safe to add entropy |
563 |
from untrusted sources - more is better than less if you need a CSPRNG. |
564 |
|
565 |
For use as PRNG, of course, this matters very little. |
566 |
|
567 |
=item $octets = $prng->get ($length) |
568 |
|
569 |
Generates and returns C<$length> random octets as a string. |
570 |
|
571 |
=back |
572 |
|
573 |
|
574 |
=head1 SEE ALSO |
575 |
|
576 |
L<http://people.csail.mit.edu/rivest/pubs/RS14.pdf>. |
577 |
|
578 |
=head1 SECURITY CONSIDERATIONS |
579 |
|
580 |
I also cannot give any guarantees for security, Spritz is a very new |
581 |
cryptographic algorithm, and when this module was written, almost |
582 |
completely unproven. |
583 |
|
584 |
=head1 AUTHOR |
585 |
|
586 |
Marc Lehmann <schmorp@schmorp.de> |
587 |
http://software.schmorp.de/pkg/Crypt-Spritz |
588 |
|
589 |
=cut |
590 |
|
591 |
1; |
592 |
|