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c65df279 | 1 | .\" -*-nroff-*- |
2 | .de VS | |
3 | .sp 1 | |
4 | .RS | |
5 | .nf | |
6 | .ft B | |
7 | .. | |
8 | .de VE | |
9 | .ft R | |
10 | .fi | |
11 | .RE | |
12 | .sp 1 | |
13 | .. | |
14 | .ie t \{\ | |
15 | . if \n(.g \{\ | |
16 | . fam P | |
17 | . \} | |
18 | .\} | |
19 | .de hP | |
20 | .IP | |
21 | .ft B | |
22 | \h'-\w'\\$1\ 'u'\\$1\ \c | |
23 | .ft P | |
24 | .. | |
25 | .ie t .ds o \(bu | |
26 | .el .ds o o | |
27 | .TH catcrypt 1 "30 September 2004" "Straylight/Edgeware" "Catacomb cryptographic library" | |
28 | .SH NAME | |
29 | catcrypt \- encrypt and decrypt messages | |
30 | .SH SYNOPSIS | |
31 | .B catcrypt | |
32 | .RB [ \-k | |
33 | .IR keyring ] | |
34 | .I command | |
35 | .PP | |
36 | where | |
37 | .I command | |
38 | is one of: | |
39 | .PP | |
40 | .B help | |
41 | .RI [ command ...] | |
42 | .br | |
43 | .B show | |
44 | .RI [ item ...] | |
45 | .br | |
46 | .B encrypt | |
cd6eca43 | 47 | .RB [ \-apC ] |
c65df279 | 48 | .RB [ \-k |
49 | .IR tag ] | |
50 | .RB [ \-f | |
51 | .IR format ] | |
52 | .RB [ \-o | |
53 | .IR output ] | |
54 | .RI [ file ] | |
55 | .br | |
56 | .B decrypt | |
cd6eca43 | 57 | .RB [ \-apqvC ] |
c65df279 | 58 | .RB [ \-f |
59 | .IR format ] | |
60 | .RB [ \-o | |
61 | .IR output ] | |
62 | .RI [ file ] | |
63 | .br | |
64 | .B encode | |
cd6eca43 | 65 | .RB [ \-p ] |
c65df279 | 66 | .RB [ \-f |
67 | .IR format ] | |
68 | .RB [ \-b | |
69 | .IR boundary ] | |
70 | .RB [ \-o | |
71 | .IR output ] | |
72 | .RI [ file ] | |
73 | .br | |
fa54fe1e | 74 | .B decode |
cd6eca43 | 75 | .RB [ \-p ] |
c65df279 | 76 | .RB [ \-f |
77 | .IR format ] | |
78 | .RB [ \-b | |
79 | .IR boundary ] | |
80 | .RB [ \-o | |
81 | .IR output ] | |
82 | .RI [ file ] | |
83 | .SH "DESCRIPTION" | |
84 | The | |
85 | .B catcrypt | |
86 | command encrypts and decrypts messages. It also works as a simple PEM | |
87 | encoder and decoder. It provides a number of subcommands, by which the | |
88 | various operations may be carried out. | |
89 | .SS "Global options" | |
90 | Before the command name, | |
91 | .I "global options" | |
92 | may be given. The following global options are supported: | |
93 | .TP | |
94 | .BR "\-h, \-\-help " [ \fIcommand ...] | |
95 | Writes a brief summary of | |
96 | .BR catcrypt 's | |
97 | various options to standard output, and returns a successful exit | |
98 | status. With command names, gives help on those commands. | |
99 | .TP | |
100 | .B "\-v, \-\-version" | |
101 | Writes the program's version number to standard output, and returns a | |
102 | successful exit status. | |
103 | .TP | |
104 | .B "\-u, \-\-usage" | |
105 | Writes a very terse command line summary to standard output, and returns | |
106 | a successful exit status. | |
107 | .TP | |
108 | .BI "\-k, \-\-keyring " file | |
109 | Names the keyring file which | |
110 | .B key | |
111 | is to process. The default keyring, used if this option doesn't specify | |
112 | one, is the file named | |
113 | .B keyring | |
114 | in the current directory. See | |
115 | .BR key (1) | |
116 | and | |
117 | .BR keyring (5) | |
118 | for more details about keyring files. | |
119 | .SH "KEY SETUP" | |
120 | Algorithms to be used with a particular key are described by attributes | |
121 | on the key, or its type. The | |
122 | .B catcrypt | |
fa54fe1e | 123 | command deals with both signing and key-encapsulation keys. (Note that |
124 | .B catcrypt | |
45c0fd36 | 125 | uses signing keys in the same way as |
fa54fe1e | 126 | .BR catsign (1).) |
c65df279 | 127 | .SS "Key-encapsulation keys" |
128 | (Key encapsulation is a means of transmitting a short, known, random | |
129 | secret to a recipient. It differs from encryption in technical ways | |
130 | which are largely uninteresting at this point.) | |
131 | .PP | |
132 | A | |
133 | .I kemalgspec | |
134 | has the syntax | |
135 | .IR kem \c | |
136 | .RB [ / \c | |
66ff643c MW |
137 | .IR bulk \c |
138 | .RB [ \- \c | |
139 | .IR cipher ] \c | |
140 | .RB [ / \c | |
141 | .IR hash ]] | |
142 | or | |
143 | .IR kem \c | |
144 | .RB [ / \c | |
c65df279 | 145 | .IR cipher \c |
146 | .RB [ / \c | |
147 | .IR hash ]]. | |
148 | If a | |
149 | .B kem | |
150 | attribute is present on the key, then it must have this form; otherwise, | |
151 | the key's type must have the form | |
152 | .BR cckem- \c | |
153 | .IR kemalgspec . | |
154 | Algorithm selections are taken from appropriately-named attributes, or, | |
155 | failing that, from the | |
156 | .IR kemalgspec . | |
157 | .PP | |
158 | The key-encapsulation mechanism is chosen according to the setting of | |
159 | .I kem | |
160 | as follows. Run | |
161 | .B catcrypt show kem | |
162 | for a list of supported KEMs. | |
163 | .TP | |
164 | .B rsa | |
165 | This is Shoup's RSA-KEM (formerly Simple RSA); see | |
166 | .I | |
167 | A proposal for an ISO standard for public key encryption (version 2.0) | |
168 | available at | |
169 | .BR http://eprint.iacr.org/2000/060/ . | |
170 | Use the | |
171 | .B rsa | |
172 | algorithm of the | |
173 | .B key add | |
174 | command (see | |
175 | .BR key (1)) | |
176 | to generate the key. | |
177 | .TP | |
178 | .B dh | |
179 | This is standard Diffie-Hellman key exchange, hashing the resulting | |
180 | shared secret to form the key, as used in, e.g., DLIES (P1363a). | |
181 | Use the | |
182 | .B dh | |
183 | algorithm of the | |
184 | .B key add | |
185 | command, preferably with the | |
186 | .B \-LS | |
187 | options, to generate the key. | |
188 | .TP | |
189 | .B ec | |
190 | This is the elliptic-curve analogue of | |
b98200ad | 191 | .BR dh . |
192 | Use the | |
c65df279 | 193 | .B ec |
194 | algorithm of the | |
195 | .BR key (1)) | |
196 | command to generate the key. | |
02dfbd5b MW |
197 | .TP |
198 | .B symm | |
199 | This is a simple symmetric encapsulation scheme. It works by hashing a | |
200 | binary key with a randomly-generated salt. Use the | |
201 | .B binary | |
202 | algorithm of the | |
203 | .B key add | |
204 | command (see | |
205 | .BR key (1)) | |
206 | to generate the key. | |
fc2d44af MW |
207 | .TP |
208 | .B x25519 | |
209 | This is Bernstein's Curve25519, a fast Diffie-Hellman using a specific | |
210 | elliptic curve. | |
211 | Use the | |
212 | .B x25519 | |
213 | algorithm of the | |
214 | .B key add | |
215 | command | |
216 | (see | |
217 | .BR key (1)) | |
218 | to generate the key. | |
643eb1bb MW |
219 | .TP |
220 | .B x448 | |
221 | This is Hamburg's Curve25519, a strong Diffie-Hellman using a specific | |
222 | elliptic curve. | |
223 | Use the | |
224 | .B x448 | |
225 | algorithm of the | |
226 | .B key add | |
227 | command | |
228 | (see | |
229 | .BR key (1)) | |
230 | to generate the key. | |
c65df279 | 231 | .PP |
66ff643c MW |
232 | The bulk crypto transform is chosen based on the |
233 | .B bulk | |
234 | attribute on the key, or, failing that, | |
235 | from the | |
236 | .I bulk | |
237 | stated in the | |
238 | .IR kemalgspec . | |
239 | Run | |
240 | .B catcrypt show bulk | |
241 | for a list of supported bulk crypto transforms. | |
242 | .TP | |
243 | .B gencomp | |
244 | A generic composition of | |
245 | a cipher secure against chosen-plaintext attack, | |
246 | and a message authentication code. | |
247 | Makes use of | |
248 | .B cipher | |
249 | and | |
250 | .B mac | |
b2973dcf MW |
251 | attributes. Run |
252 | .B catcrypt show cipher | |
253 | for a list of supported symmetric encryption algorithms; the default | |
254 | .I cipher | |
255 | is | |
256 | .BR blowfish-cbc . | |
66ff643c | 257 | This is the default transform. |
d9d419b0 MW |
258 | .TP |
259 | .B naclbox | |
260 | Use Salsa20 or ChaCha and Poly1305 to secure the bulk data. | |
261 | This is nearly the same as the NaCl | |
262 | .B crypto_secretbox | |
263 | construction, | |
264 | except that | |
265 | .B catcrypt | |
266 | uses Salsa20 or ChaCha rather than XSalsa20, | |
267 | because it doesn't need the latter's extended nonce. | |
268 | The | |
269 | .B cipher | |
270 | attribute may be set to one of | |
271 | .BR salsa20 , | |
272 | .BR salsa20/12 , | |
273 | .BR salsa20/8 , | |
274 | .BR chacha20 , | |
275 | .BR chacha12 , | |
276 | or | |
277 | .BR chacha8 ; | |
278 | the default is | |
279 | .BR salsa20 . | |
66ff643c | 280 | .PP |
c65df279 | 281 | As well as the KEM itself, a number of supporting algorithms are used. |
282 | These are taken from appropriately named attributes on the key or, | |
283 | failing that, derived from other attributes as described below. | |
284 | .TP | |
285 | .B cipher | |
66ff643c MW |
286 | This is the symmetric encryption algorithm |
287 | used by the bulk data transform. | |
288 | If there is no | |
c65df279 | 289 | .B cipher |
290 | attribute then the | |
66ff643c | 291 | .I bulk |
c65df279 | 292 | in the |
293 | .I kemalgspec | |
b2973dcf MW |
294 | is used; if that it absent, then the default depends on the bulk |
295 | transform. | |
c65df279 | 296 | .TP |
297 | .B hash | |
298 | This is the hash function used to distil entropy from the shared secret | |
299 | constructed by the raw KEM. If there is no | |
300 | .B hash | |
301 | attribute then the | |
302 | .I hash | |
303 | in the | |
b98200ad | 304 | .I kemalgspec |
305 | is used; if that is absent then the default of | |
c65df279 | 306 | .B rmd160 |
307 | is used. Run | |
308 | .B catcrypt show hash | |
309 | for a list of supported symmetric encryption algorithms. | |
310 | .TP | |
311 | .B mac | |
66ff643c MW |
312 | This is the message authentication algorithm |
313 | used by the | |
314 | .B gencomp | |
315 | bulk data transform | |
316 | to ensure integrity of the encrypted message and | |
317 | defend against chosen-ciphertext attacks. | |
318 | If there is no | |
c65df279 | 319 | .B mac |
320 | attribute then | |
321 | .IB hash -hmac | |
322 | is chosen as a default. Run | |
323 | .B catcrypt show mac | |
324 | for a list of supported message authentication algorithms. | |
325 | .TP | |
326 | .B kdf | |
327 | This is the key derivation function used to stretch the hashed shared | |
328 | secret to a sufficient length to select symmetric encryption and | |
329 | authentication keys, initialization vectors and other necessary | |
330 | pseudorandom quantities. If there is no | |
331 | .B kdf | |
332 | attribute then | |
333 | .IB hash -mgf | |
334 | is chosen as a default. Run | |
335 | .B catcrypt show kdf | |
336 | for a list of supported key derivation functions. | |
337 | .B Caution! | |
338 | Not all supported functions have the required security features: don't | |
339 | override the default choice unless you know what you're doing. | |
340 | .SS "Signing keys" | |
341 | A | |
342 | .I sigalgspec | |
343 | has the form | |
344 | .IR sig \c | |
345 | .RB [ / \c | |
346 | .IR hash ]. | |
347 | If a | |
348 | .B sig | |
349 | attribute is present on the key, then it must have this form; otherwise, | |
350 | the key's type must have the form | |
351 | .BI ccsig- \c | |
352 | .IR sigalgspec . | |
353 | Algorithm selections are taken from appropriately-named attributes, or, | |
354 | failing that, from the | |
355 | .IR sigalgspec . | |
356 | .PP | |
357 | The signature algorithm is chosen according to the setting of | |
358 | .I sig | |
359 | as follows. Run | |
360 | .B catcrypt show sig | |
361 | for a list of supported signature algorithms. | |
362 | .TP | |
363 | .B rsapkcs1 | |
364 | This is almost the same as the RSASSA-PKCS1-v1_5 algorithm described in | |
365 | RFC3447; the difference is that the hash is left bare rather than being | |
45c0fd36 | 366 | wrapped in a DER-encoded |
c65df279 | 367 | .B DigestInfo |
368 | structure. This doesn't affect security since the key can only be used | |
369 | with the one hash function anyway, and dropping the DER wrapping permits | |
370 | rapid adoption of new hash functions. Regardless, use of this algorithm | |
371 | is not recommended, since the padding method has been shown vulnerable | |
372 | to attack. Use the | |
373 | .B rsa | |
374 | algorithm of the | |
375 | .B key add | |
376 | command (see | |
377 | .BR key (1)) | |
378 | to generate the key. | |
379 | .TP | |
380 | .B rsapss | |
381 | This is the RSASSA-PSS algorithm described in RFC3447. It is the | |
382 | preferred RSA-based signature scheme. Use the | |
383 | .B rsa | |
384 | algorithm of the | |
385 | .B key add | |
386 | command (see | |
387 | .BR key (1)) | |
388 | to generate the key. | |
389 | .TP | |
390 | .B dsa | |
45c0fd36 | 391 | This is the DSA algorithm described in FIPS180-1 and FIPS180-2. Use the |
c65df279 | 392 | .B dsa |
393 | algorithm of the | |
394 | .B key add | |
395 | command (see | |
396 | .BR key (1)) | |
397 | to generate the key. | |
398 | .TP | |
399 | .B ecdsa | |
400 | This is the ECDSA algorithm described in ANSI X9.62 and FIPS180-2. Use | |
401 | the | |
402 | .B ec | |
403 | algorithm of the | |
404 | .B key add | |
405 | command (see | |
406 | .BR key (1)) | |
407 | to generate the key. | |
408 | .TP | |
409 | .B kcdsa | |
410 | This is the revised KCDSA (Korean Certificate-based Digital Signature | |
411 | Algorithm) described in | |
412 | .I The Revised Version of KCDSA | |
413 | .RB ( http://dasan.sejong.ac.kr/~chlim/pub/kcdsa1.ps ). | |
414 | Use the | |
415 | .B dh | |
416 | algorithm of the | |
417 | .B key add | |
418 | command with the | |
419 | .B \-LS | |
420 | options (see | |
421 | .BR key (1)) | |
422 | to generate the key. | |
423 | .TP | |
424 | .B eckcdsa | |
425 | This is an unofficial elliptic-curve analogue of the KCDSA algorithm. | |
426 | Use the | |
427 | .B ec | |
428 | algorithm of the | |
429 | .B key add | |
430 | command (see | |
431 | .BR key (1)) | |
432 | to generate the key. | |
02dfbd5b | 433 | .TP |
d56fd9d1 MW |
434 | .B ed25519 |
435 | This is Bernstein, Duif, Lange, Schwabe, and Yang's Ed25519 algorithm. | |
436 | More specifically, this is HashEd25519 | |
437 | using the selected | |
438 | .B hash | |
439 | algorithm \(en by default | |
440 | .BR sha512 . | |
441 | Use the | |
442 | .B ed25519 | |
443 | algorithm of the | |
444 | .B key add | |
445 | command | |
446 | (see | |
447 | .BR key (1)) | |
448 | to generate the key. | |
449 | .TP | |
c578d5d8 MW |
450 | .B ed448 |
451 | This is Bernstein, Duif, Lange, Schwabe, and Yang's EdDSA algorithm, | |
452 | using Hamburg's Ed448-Goldilocks elliptic curve, | |
453 | as specified in RFC8032. | |
454 | More specifically, this is HashEd448 | |
455 | using the selected | |
456 | .B hash | |
457 | algorithm \(en by default | |
458 | .BR sha3-512 . | |
459 | Use the | |
460 | .B ed448 | |
461 | algorithm of the | |
462 | .B key add | |
463 | command | |
464 | (see | |
465 | .BR key (1)) | |
466 | to generate the key. | |
467 | .TP | |
02dfbd5b MW |
468 | .B mac |
469 | This uses a symmetric message-authentication algorithm rather than a | |
470 | digital signature. The precise message-authentication scheme used is | |
471 | determined by the | |
472 | .B mac | |
473 | attribute on the key, which defaults to | |
474 | .IB hash -hmac | |
475 | if unspecified. Use the | |
476 | .B binary | |
477 | algorithm of the | |
478 | .B key add | |
479 | command (see | |
480 | .BR key (1)) | |
481 | to generate the key. | |
c65df279 | 482 | .PP |
483 | As well as the signature algorithm itself, a hash function is used. | |
484 | This is taken from the | |
485 | .B hash | |
486 | attribute on the key, or, failing that, from the | |
487 | .I hash | |
488 | specified in the | |
489 | .IR sigalgspec , | |
490 | or, if that is absent, determined by the signature algorithm as follows. | |
491 | .hP \*o | |
492 | For | |
493 | .BR rsapkcs1 , | |
494 | .BR rsapss , | |
495 | .BR dsa , | |
496 | and | |
497 | .BR ecdsa , | |
498 | the default hash function is | |
499 | .BR sha . | |
500 | .hP \*o | |
501 | For | |
45c0fd36 | 502 | .BR kcdsa |
c65df279 | 503 | and |
504 | .BR eckcdsa , | |
505 | the default hash function is | |
506 | .BR has160 . | |
df8800f1 MW |
507 | For |
508 | .BR ed25519 , | |
509 | the default hash function is | |
510 | .BR sha512 . | |
c578d5d8 MW |
511 | For |
512 | .BR ed448 , | |
513 | the default hash function is | |
514 | .BR shake256 . | |
c65df279 | 515 | .PP |
516 | Run | |
517 | .B catcrypt show hash | |
518 | for a list of supported hash functions. | |
519 | .SH "ENCODINGS" | |
520 | Two encodings for the ciphertext are supported. | |
521 | .TP | |
522 | .B binary | |
523 | The raw format, which has the benefit of being smaller, but needs to be | |
524 | attached to mail messages and generally handled with care. | |
525 | .TP | |
526 | .B pem | |
527 | PEM-encapsulated Base-64 encoded text. This format can be included | |
528 | directly in email and picked out again automatically; but there is a | |
529 | 4-to-3 data expansion as a result. | |
530 | .SH "COMMAND REFERENCE" | |
531 | .SS help | |
532 | The | |
533 | .B help | |
534 | command behaves exactly as the | |
535 | .B \-\-help | |
536 | option. With no arguments, it shows an overview of | |
537 | .BR catcrypt 's | |
538 | options; with arguments, it describes the named subcommands. | |
539 | .SS show | |
540 | The | |
541 | .B show | |
542 | command prints various lists of tokens understood by | |
543 | .BR catcrypt . | |
544 | With no arguments, it prints all of the lists; with arguments, it prints | |
545 | just the named lists, in order. The recognized lists can be enumerated | |
546 | using the | |
547 | .VS | |
548 | catcrypt show list | |
549 | .VE | |
550 | command. The lists are as follows. | |
551 | .TP | |
552 | .B list | |
553 | The lists which can be enumerated by the | |
554 | .B show | |
555 | command. | |
556 | .TP | |
557 | .B kem | |
558 | The key-encapsulation algorithms which can be used in a | |
559 | key-encapsulation key's | |
560 | .B kem | |
561 | attribute. | |
562 | .TP | |
563 | .B cipher | |
564 | The symmetric encryption algorithms which can be used in a | |
565 | key-encapsulation key's | |
566 | .B cipher | |
b2973dcf MW |
567 | attribute when using the |
568 | .B gencomp | |
569 | bulk transform. | |
c65df279 | 570 | .TP |
571 | .B mac | |
572 | The message authentication algorithms which can be used in a | |
573 | key-encapsulation key's | |
574 | .B mac | |
575 | attribute. | |
576 | .TP | |
577 | .B sig | |
578 | The signature algorithms which can be used in a signing key's | |
579 | .B sig | |
580 | attribute. | |
581 | .TP | |
582 | .B hash | |
583 | The hash functions which can be used in a key's | |
584 | .B hash | |
585 | attribute. | |
586 | .TP | |
587 | .B enc | |
45c0fd36 | 588 | The encodings which can be applied to encrypted messages; see |
c65df279 | 589 | .B ENCODINGS |
590 | above. | |
591 | .SS encrypt | |
592 | The | |
593 | .B encrypt | |
594 | command encrypts a file and writes out the appropriately-encoded | |
595 | ciphertext. By default, it reads from standard input and writes to | |
596 | standard output. If a filename argument is given, this file is read | |
597 | instead (as binary data). | |
598 | .PP | |
599 | The following options are recognized. | |
600 | .TP | |
601 | .B "\-a, \-\-armour" | |
602 | Produce ASCII-armoured output. This is equivalent to specifying | |
603 | .BR "\-f pem" . | |
604 | The variant spelling | |
605 | .B "\-\-armor" | |
606 | is also accepted. | |
607 | .TP | |
608 | .BI "\-f, \-\-format " format | |
609 | Produce output encoded according to | |
610 | .IR format . | |
611 | .TP | |
612 | .BI "\-k, \-\-key " tag | |
613 | Use the key-encapsulation key named | |
614 | .I tag | |
615 | in the current keyring; the default key is | |
616 | .BR ccrypt . | |
617 | .TP | |
cd6eca43 MW |
618 | .BI "\-p, \-\-progress" |
619 | Write a progress meter to standard error while processing large files. | |
620 | .TP | |
c65df279 | 621 | .BI "\-s, \-\-sign-key " tag |
622 | Use the signature key named | |
623 | .I tag | |
624 | in the current keyring; the default is not to sign the ciphertext. | |
625 | .TP | |
626 | .BI "\-o, \-\-ouptut " file | |
627 | Write output to | |
628 | .I file | |
629 | rather than to standard output. | |
946c3f72 | 630 | .TP |
631 | .B "\-C, \-\-nocheck" | |
632 | Don't check the public key for validity. This makes encryption go much | |
633 | faster, but at the risk of using a duff key. | |
c65df279 | 634 | .SS decrypt |
635 | The | |
636 | .B decrypt | |
637 | command decrypts a ciphertext and writes out the plaintext. By default, | |
638 | it reads from standard input and writes to standard output. If a | |
639 | filename argument is given, this file is read instead. | |
640 | .PP | |
641 | The following options are recognized. | |
642 | .TP | |
643 | .B "\-a, \-\-armour" | |
fa54fe1e | 644 | Read ASCII-armoured input. This is equivalent to specifying |
c65df279 | 645 | .BR "\-f pem" . |
646 | The variant spelling | |
647 | .B "\-\-armor" | |
648 | is also accepted. | |
649 | .TP | |
fa54fe1e | 650 | .B "\-b, \-\-buffer" |
651 | Buffer plaintext data until we're sure we've got it all. This is forced | |
652 | on if output is to stdout, but is always available as an option. | |
653 | .TP | |
c65df279 | 654 | .BI "\-f, \-\-format " format |
655 | Read input encoded according to | |
656 | .IR format . | |
657 | .TP | |
cd6eca43 MW |
658 | .BI "\-p, \-\-progress" |
659 | Write a progress meter to standard error while processing large files. | |
660 | .TP | |
c65df279 | 661 | .B "\-v, \-\-verbose" |
662 | Produce more verbose messages. See below for the messages produced | |
663 | during decryption. The default verbosity level is 1. (Currently this | |
664 | is the most verbose setting. This might not be the case always.) | |
665 | .TP | |
666 | .B "\-q, \-\-quiet" | |
667 | Produce fewer messages. | |
668 | .TP | |
669 | .BI "\-o, \-\-output " file | |
670 | Write output to | |
671 | .I file | |
672 | instead of to standard output. The file is written in binary mode. | |
673 | Fixing line-end conventions is your problem; there are lots of good | |
674 | tools for dealing with it. | |
946c3f72 | 675 | .TP |
676 | .B "\-C, \-\-nocheck" | |
677 | Don't check the private key for validity. This makes decryption go much | |
678 | faster, but at the risk of using a duff key, and possibly leaking | |
679 | information about the private key. | |
c65df279 | 680 | .PP |
681 | Output is written to standard output in a machine-readable format. | |
682 | Major problems cause the program to write a diagnostic to standard error | |
683 | and exit nonzero as usual. The quantity of output varies depending on | |
684 | the verbosity level and whether the plaintext is also being written to | |
fa54fe1e | 685 | standard output. Output lines begin with a keyword: |
c65df279 | 686 | .TP |
687 | .BI "FAIL " reason | |
688 | An error prevented decryption. The program will exit nonzero. | |
689 | .TP | |
690 | .BI "WARN " reason | |
691 | .B catcrypt | |
692 | encountered a situation which may or may not invalidate the decryption. | |
45c0fd36 | 693 | .TP |
c65df279 | 694 | .BI "OK " message |
695 | Decryption was successful. This is only produced if main output is | |
696 | being sent somewhere other than standard output. | |
697 | .TP | |
698 | .B "DATA" | |
699 | The plaintext follows, starting just after the next newline character or | |
b98200ad | 700 | sequence. This is only produced if main output is also being sent to |
fa54fe1e | 701 | standard output. |
c65df279 | 702 | .TP |
703 | .BI "INFO " note | |
704 | Any other information. | |
705 | .PP | |
706 | The information written at the various verbosity levels is as follows. | |
707 | .hP 0. | |
708 | No output. Watch the exit status. | |
709 | .hP 1. | |
710 | All messages. | |
711 | .PP | |
712 | .B Warning! | |
fa54fe1e | 713 | All output written has been checked for authenticity. However, output |
77e4471a | 714 | can fail midway through for many reasons, and the resulting message may |
45c0fd36 | 715 | therefore be truncated. Don't rely on the output being complete until |
4224d0b9 | 716 | .B OK |
717 | is printed or | |
c65df279 | 718 | .B catcrypt decrypt |
fa54fe1e | 719 | exits successfully. |
c65df279 | 720 | .SS "encode" |
721 | The | |
722 | .B encode | |
723 | command encodes an input file according to one of the encodings | |
724 | described above in | |
725 | .BR ENCODINGS . | |
45c0fd36 | 726 | The input is read from the |
c65df279 | 727 | .I file |
728 | given on the command line, or from standard input if none is specified. | |
729 | Options provided are: | |
730 | .TP | |
cd6eca43 MW |
731 | .BI "\-p, \-\-progress" |
732 | Write a progress meter to standard error while processing large files. | |
733 | .TP | |
c65df279 | 734 | .BI "\-f, \-\-format " format |
735 | Produce output in | |
736 | .IR format . | |
737 | Run | |
738 | .B catcrypt show enc | |
739 | for a list of encoding formats. | |
740 | .TP | |
741 | .BI "\-b, \-\-boundary " label | |
742 | Set the PEM boundary string to | |
743 | .IR label ; | |
744 | i.e., assuming we're encoding in PEM format, the output will have | |
745 | .BI "\-\-\-\-\-BEGIN " label "\-\-\-\-\-" | |
746 | at the top and | |
747 | .BI "\-\-\-\-\-END " label "\-\-\-\-\-" | |
748 | at the bottom. The default | |
749 | .I label | |
750 | is | |
751 | .BR MESSAGE . | |
752 | .TP | |
753 | .BI "\-o, \-\-output " file | |
754 | Write output to | |
755 | .I file | |
756 | instead of to standard output. | |
757 | .SS "decode" | |
758 | The | |
759 | .B decode | |
760 | command decodes an input file encoded according to one of the encodings | |
761 | described above in | |
762 | .BR ENCODINGS . | |
45c0fd36 | 763 | The input is read from the |
c65df279 | 764 | .I file |
765 | given on the command line, or from standard input if none is specified. | |
766 | Options provided are: | |
767 | .TP | |
768 | .BI "\-f, \-\-format " format | |
769 | Decode input in | |
770 | .IR format . | |
771 | Run | |
772 | .B catcrypt show enc | |
773 | for a list of encoding formats. | |
774 | .TP | |
775 | .BI "\-b, \-\-boundary " label | |
776 | Set the PEM boundary string to | |
777 | .IR label ; | |
778 | i.e., assuming we're encoding in PEM format, start processing input | |
779 | between | |
780 | .BI "\-\-\-\-\-BEGIN " label "\-\-\-\-\-" | |
45c0fd36 | 781 | and |
c65df279 | 782 | .BI "\-\-\-\-\-END " label "\-\-\-\-\-" |
783 | lines. Without this option, | |
784 | .B catcrypt | |
785 | will start reading at the first plausible boundary string, and continue | |
786 | processing until it reaches the matching end boundary. | |
787 | .TP | |
cd6eca43 MW |
788 | .BI "\-p, \-\-progress" |
789 | Write a progress meter to standard error while processing large files. | |
790 | .TP | |
c65df279 | 791 | .BI "\-o, \-\-output " file |
792 | Write output to | |
793 | .I file | |
794 | instead of to standard output. | |
795 | .SH "SECURITY PROPERTIES" | |
796 | Assuming the security of the underlying primitive algorithms, the | |
797 | following security properties of the ciphertext hold. | |
798 | .hP \*o | |
799 | An adversary given the public key-encapsulation key and capable of | |
800 | requesting encryption of arbitrary plaintexts of his own devising is | |
801 | unable to decide whether he is given ciphertexts corresponding to his | |
802 | chosen plaintexts or random plaintexts of the same length. This holds | |
803 | even if the adversary is permitted to request decryption of any | |
804 | ciphertext other than one produced as a result of an encryption request. | |
805 | This property is called | |
806 | .BR IND-CCA2 . | |
807 | .hP \*o | |
808 | An adversary given the public key-encapsulation and verification keys, | |
809 | and capable of requesting encryption of arbitrary plaintext of his own | |
810 | devising is unable to produce a new ciphertext which will be accepted as | |
811 | genuine. This property is called | |
812 | .BR INT-CTXT . | |
813 | .hP \*o | |
814 | An adversary given the public key-encapsulation and verification keys, | |
815 | and capable of requesting encryption of arbitrary plaintext of his own | |
816 | devising is unable to decide whether the ciphertexts he is given are | |
817 | correctly signed. This property doesn't seem to have a name. | |
818 | .PP | |
819 | Not all is rosy. If you leak intermediate values during decryption then | |
820 | an adversary can construct a new correctly-signed message. Don't do | |
821 | that, then \(en leaking intermediate values often voids security | |
822 | warranties. But it does avoid the usual problem with separate signing | |
823 | and encryption that a careful leak by the recipient can produce evidence | |
824 | that you signed some incriminating message. | |
4224d0b9 | 825 | .PP |
826 | Note that | |
827 | .BR catcrypt 's | |
828 | signatures do | |
829 | .I not | |
830 | provide `non-repudiation' in any useful way. This is deliberate: the | |
831 | purpose of signing is to convince the recipient of the sender's | |
832 | identity, rather than to allow the recipient to persuade anyone else. | |
833 | Indeed, given an encrypted and signed message, the recipient can | |
834 | straightforwardly construct a new message, apparently from the same | |
835 | sender, and whose signature still verifies, but with arbitrarily chosen | |
836 | content. | |
c65df279 | 837 | .SH "CRYPTOGRAPHIC THEORY" |
838 | Encryption of a message proceeds as follows. | |
839 | .hP 0. | |
840 | Emit a header packet containing the key-ids for the key-encapsulation | |
841 | key, and signature key if any. | |
842 | .hP 1. | |
843 | Use the KEM to produce a public value and a shared secret the recipient | |
844 | will be able to extract from the public value using his private key. | |
845 | Emit a packet containing the public value. | |
846 | .hP 2. | |
847 | Hash the shared secret. Use the KDF to produce a pseudorandom keystream | |
848 | of indefinite length. | |
849 | .hP 3. | |
850 | Use the first bits of the keystream to key a symmetric encryption | |
851 | scheme; use the next bits to key a message authentication code. | |
852 | .hP 4. | |
853 | If we're signing the message then extract 1024 bytes from the keystream, | |
f9e51332 | 854 | sign the header and public value, and the keystream bytes; emit a packet |
855 | containing the signature. The signature packet doesn't contain the | |
856 | signed message, just the signature. | |
c65df279 | 857 | .hP 5. |
858 | Split the message into blocks. For each block, pick a random IV from | |
859 | the keystream, encrypt the block and emit a packet containing the | |
aaa2361e | 860 | IV, ciphertext, and a MAC tag over the ciphertext and a sequence number. |
861 | .hP 6. | |
862 | The last chunk is the encryption of an empty plaintext block. No | |
863 | previous plaintext block is empty. This lets us determine the | |
864 | difference between a complete file and one that's been maliciously | |
865 | truncated. | |
c65df279 | 866 | .PP |
867 | That's it. Nothing terribly controversial, really. | |
868 | .SH "SEE ALSO" | |
869 | .BR key (1), | |
fa54fe1e | 870 | .BR catsign (1), |
c65df279 | 871 | .BR dsig (1), |
872 | .BR hashsum (1), | |
873 | .BR keyring (5). | |
874 | .SH AUTHOR | |
f387fcb1 | 875 | Mark Wooding, <mdw@distorted.org.uk> |