22 \h'-\w'\\$1\ 'u'\\$1\ \c
27 .TH catsign 1 "17 March 2005" "Straylight/Edgeware" "Catacomb cryptographic library"
29 catsign \- sign and verify messages
114 command signs and verifies messages. It also works as a simple PEM
115 encoder and decoder. It provides a number of subcommands, by which the
116 various operations may be carried out.
118 Before the command name,
120 may be given. The following global options are supported:
122 .BR "\-h, \-\-help " [ \fIcommand ...]
123 Writes a brief summary of
125 various options to standard output, and returns a successful exit
126 status. With command names, gives help on those commands.
128 .B "\-v, \-\-version"
129 Writes the program's version number to standard output, and returns a
130 successful exit status.
133 Writes a very terse command line summary to standard output, and returns
134 a successful exit status.
136 .BI "\-k, \-\-keyring " file
137 Names the keyring file which
139 is to process. The default keyring, used if this option doesn't specify
140 one, is the file named
142 in the current directory. See
146 for more details about keyring files.
148 Algorithms to be used with a particular key are described by attributes
149 on the key, or its type. The
151 command deals with signing keys. (Note that
153 uses signing keys in the same way as
164 attribute is present on the key, then it must have this form; otherwise,
165 the key's type must have the form
168 Algorithm selections are taken from appropriately-named attributes, or,
169 failing that, from the
172 The signature algorithm is chosen according to the setting of
176 for a list of supported signature algorithms.
179 This is almost the same as the RSASSA-PKCS1-v1_5 algorithm described in
180 RFC3447; the difference is that the hash is left bare rather than being
181 wrapped in a DER-encoded
183 structure. This doesn't affect security since the key can only be used
184 with the one hash function anyway, and dropping the DER wrapping permits
185 rapid adoption of new hash functions. Regardless, use of this algorithm
186 is not recommended, since the padding method has been shown vulnerable
196 This is the RSASSA-PSS algorithm described in RFC3447. It is the
197 preferred RSA-based signature scheme. Use the
206 This is the DSA algorithm described in FIPS180-1 and FIPS180-2. Use the
215 This is the ECDSA algorithm described in ANSI X9.62 and FIPS180-2. Use
225 This is the revised KCDSA (Korean Certificate-based Digital Signature
226 Algorithm) described in
227 .I The Revised Version of KCDSA
228 .RB ( http://dasan.sejong.ac.kr/~chlim/pub/kcdsa1.ps ).
240 This is an unofficial elliptic-curve analogue of the KCDSA algorithm.
250 This uses a symmetric message-authentication algorithm rather than a
251 digital signature. The precise message-authentication scheme used is
254 attribute on the key, which defaults to
256 if unspecified. Use the
264 As well as the signature algorithm itself, a hash function is used.
265 This is taken from the
267 attribute on the key, or, failing that, from the
271 or, if that is absent, determined by the signature algorithm as follows.
279 the default hash function is
286 the default hash function is
291 for a list of supported hash functions.
293 Two encodings for the ciphertext are supported.
296 The raw format, which has the benefit of being smaller, but needs to be
297 attached to mail messages and generally handled with care.
300 PEM-encapsulated Base-64 encoded text. This format can be included
301 directly in email and picked out again automatically; but there is a
302 4-to-3 data expansion as a result.
303 .SH "SIGNATURE FORMATS"
304 There are two basic signature formats understood by
307 Embedded signatures include (embed) the message they sign; hence they're
308 complete in and of themselves. The
310 program extracts the message during signature verification.
312 Detached signatures are separate from the messages they sign, and both
313 the original file and the signature are required for a successful
316 Another important distinction is whether the message data is considered
317 to be plain text or raw binary data.
319 When dealing with plain text,
321 allows a limited quantity of leeway in the messages it processes. It
322 ignores trailing whitespace on a line, including stray carriage-returns,
323 which may appear if Windows boxes have had their way with the data. It
324 also appends a final newline if there wasn't one before. In embedded
325 signatures, the text is left unencoded, so that the message is readable.
327 Binary files are preserved completely, and no variation whatever is
334 command can convert between detached and embedded signatures; it cannot
335 convert between binary and text mode signatures. (The data actually
336 signed includes a flag saying whether the message is textual. The
337 rationale here is that what looks like an ASCII space before a newline
338 may be devastatingly significant in a binary data file, and if a message
339 is signed as raw binary then no changes whatever should be allowed.)
340 .SH "COMMAND REFERENCE"
344 command behaves exactly as the
346 option. With no arguments, it shows an overview of
348 options; with arguments, it describes the named subcommands.
352 command prints various lists of tokens understood by
354 With no arguments, it prints all of the lists; with arguments, it prints
355 just the named lists, in order. The recognized lists can be enumerated
360 command. The lists are as follows.
363 The lists which can be enumerated by the
368 The signature algorithms which can be used in a signing key's
373 The hash functions which can be used in a key's
378 The encodings which can be applied to encrypted messages; see
384 command signs a message and writes out an appropriately-encoded
385 signature. By default, it reads a message from standard input and
386 writes the signature to standard output. If a filename argument is
387 given, this file is read instead.
389 The following options are recognized.
392 Produce ASCII-armoured output. This is equivalent to specifying
399 Read and sign the input as binary data. The default is to treat the
403 Produce a detached signature. The default is to produce a signature
404 with embedded message.
406 .BI "\-f, \-\-format " format
407 Produce output encoded according to
410 .BI "\-k, \-\-key " tag
411 Use the signing key named
413 in the current keyring; the default key is
416 .BI "\-o, \-\-ouptut " file
419 rather than to standard output.
421 .BI "\-p, \-\-progress"
422 Write a progress meter to standard error while processing large files.
425 Read and sign the input as text. This is the default.
427 .B "\-C, \-\-nocheck"
428 Don't check the private key for validity. This makes signing go much
429 faster, but at the risk of using a duff key, and potentially leaking
430 information about the private key.
434 command checks a signature's validity, producing as output information
435 about the signature and the signed message.
437 The first non-option argument is the name of the file containing the
438 signature data; this may be omitted or
440 to indicate that the signature be read from standard input. The second
441 non-option argument, if any, is the name of the file to read the message
442 from, if the signature is detached. An error is reported if a message
443 file is specified but the signature contains an embedded message
444 already; if the signature is detached but no filename is given, then the
445 message is expected on stdin (immediately after the signature, if any).
448 Read ASCII-armoured input. This is equivalent to specifying
455 Buffer the message until the signature is verified. This is forced on
456 if output is to stdout, but is always available as an option.
458 .BI "\-f, \-\-format " format
459 Read input encoded according to
462 .B "\-v, \-\-verbose"
463 Produce more verbose messages. See below for the messages produced
464 during decryption. The default verbosity level is 1. (Currently this
465 is the most verbose setting. This might not be the case always.)
467 .BI "\-p, \-\-progress"
468 Write a progress meter to standard error while processing large files.
471 Produce fewer messages.
473 .BI "\-k, \-\-key " tag
476 uses the signature header to work out which key to use to verify a
477 signature. Using this option causes verification to fail unless the
478 signature header specifies the key named
481 .BI "\-t, \-\-freshtime " time
482 Only accept signatures claiming to have been made more recently than
488 (the default) then any timestamp in the past is acceptable.
491 Show the datestamp in the signature in UTC rather than (your) local
496 .BI "\-o, \-\-output " file
497 Write the verified message to
499 The file is written in text or binary
500 mode as appropriate. The default is to write the message to standard
501 output unless verifying a detached signature, in which case nothing is
504 .B "\-C, \-\-nocheck"
505 Don't check the public key for validity. This makes verification go
506 much faster, but at the risk of using a duff key, and potentially
507 accepting false signatures.
509 Output is written to standard output in a machine-readable format.
510 Major problems cause the program to write a diagnostic to standard error
511 and exit nonzero as usual. The quantity of output varies depending on
512 the verbosity level and whether the message is also being written to
513 standard output. Output lines begin with a keyword:
516 An error prevented verification. The program will exit nonzero.
520 encountered a situation which may or may not invalidate the
524 Verification was successful. This is only produced if the message is
525 being sent somewhere other than standard output.
528 The message follows, starting just after the next newline character or
529 sequence. This is only produced if the message is being written to
533 Any other information.
535 The information written at the various verbosity levels is as follows.
537 No output. Watch the exit status.
542 All output written has been checked for authenticity. However, output
543 can fail madway through for many reasons, and the resulting message may
544 therefore be truncated. Don't rely on the output being complete until
552 command analyses a signature without verifying it, and prints
553 interesting information about it. This might be useful for diagnostic
554 purposes. No keys are needed for this operation, though you get more
555 useful information if you have them.
557 If a non-option argument is given, and it is not
559 then it is taken to name the file containing the signature to parse;
560 otherwise a signature is read from standard input.
562 The following options are recognized.
565 Read ASCII-armoured input. This is equivalent to specifying
571 .BI "\-f, \-\-format " format
572 Read input encoded according to
575 .BI "\-p, \-\-progress"
576 Write a progress meter to standard error while processing large files.
579 Show the datestamp in the signature in UTC rather than (your) local
584 A description of the signature block is produced on standard output; it
585 is mostly machine-readable. The first word on each line explains what
586 kind of output it is.
589 The signature data is invalid and cannot be parsed.
592 Something is wrong with the data, but isn't fatal.
595 An environmental problem means that the information isn't as helpful as
596 it might be. For example, the keyring file can't be opened, so we don't
597 know whether the verification key is there.
599 .BI "INFO flags " flags
600 Describes the flags set in the signature header. The
602 are a list of flags, one per word, preceded by a
604 if the flag is clear.
606 .BI "INFO expected-flags " flags
607 If the PEM boundary string didn't match the actual signature data then
608 this line is output, listing the expected flags and their settings.
609 Problems with boundary mismatches can be resolved using the
613 .BI "INFO date " yyyy "\-" mm "\-" dd " " hh ":" mm ":" ss " " tz
614 Signature was (allegedly!) made at the given time and date. If the
616 option was given, this will be in UTC.
619 Signature was (allegedly!) made using the key
621 which is present in the current keyring.
623 .BI "INFO unknown-key " keyid
624 Signature was (allegedly!) made using the key with id
626 which is not in the current keyring (or the keyring wasn't found).
630 command translates signatures between the various supported formats.
631 This is a (slightly) more complex operation than re-encoding, though it
632 does not require any cryptographic operations.
634 The first non-option argument is the name of the file containing the
635 signature data; this may be omitted or
637 to indicate that the signature be read from standard input. The second
638 non-option argument, if any, is the name of the file to read the message
639 from, if the signature is detached. An error is reported if a message
640 file is specified but the signature contains an embedded message
641 already; if the signature is detached but no filename is given, then the
642 message is expected on stdin (immediately after the signature, if any).
644 The options follow a rough convention: options describing the input
645 format are lower-case and options specifying the output format are
646 upper-case. The following options are recognized.
648 .BI "\-a, \-\-armour-in"
649 Read ASCII-armoured input. This is equivalent to specifying
655 .BI "\-p, \-\-progress"
656 Write a progress meter to standard error while processing large files.
658 .BI "\-A, \-\-armour-out"
659 Produce ASCII-armoured output. This is equivalent to specifying
666 Produce a detached signature. This may be used to detach a signature
667 from an embedded message.
670 Produce a signature with embedded message. This may be used to
671 reattach a message to its detached signature.
673 .BI "\-f, \-\-format-in " format
674 Read input encoded according to
677 .BI "\-F, \-\-format-out " format
678 Produce output encoded according to
681 .BI "\-m, \-\-message " file
688 then write the message to standard output. Don't send the message and
689 signature to the same place because it doesn't work.
691 .BI "\-o, \-\-output " file
692 Write the signature to
698 option is given, a signature is written to standard output.
702 command encodes an input file according to one of the encodings
705 The input is read from the
707 given on the command line, or from standard input if none is specified.
708 Options provided are:
710 .BI "\-f, \-\-format " format
715 for a list of encoding formats.
717 .BI "\-b, \-\-boundary " label
718 Set the PEM boundary string to
720 i.e., assuming we're encoding in PEM format, the output will have
721 .BI "\-\-\-\-\-BEGIN " label "\-\-\-\-\-"
723 .BI "\-\-\-\-\-END " label "\-\-\-\-\-"
724 at the bottom. The default
729 .BI "\-p, \-\-progress"
730 Write a progress meter to standard error while processing large files.
732 .BI "\-o, \-\-output " file
735 instead of to standard output.
739 command decodes an input file encoded according to one of the encodings
742 The input is read from the
744 given on the command line, or from standard input if none is specified.
745 Options provided are:
747 .BI "\-f, \-\-format " format
752 for a list of encoding formats.
754 .BI "\-b, \-\-boundary " label
755 Set the PEM boundary string to
757 i.e., assuming we're encoding in PEM format, start processing input
759 .BI "\-\-\-\-\-BEGIN " label "\-\-\-\-\-"
761 .BI "\-\-\-\-\-END " label "\-\-\-\-\-"
762 lines. Without this option,
764 will start reading at the first plausible boundary string, and continue
765 processing until it reaches the matching end boundary.
767 .BI "\-p, \-\-progress"
768 Write a progress meter to standard error while processing large files.
770 .BI "\-o, \-\-output " file
773 instead of to standard output.
775 The trailing-whitespace deletion doesn't work for more than 32K of
776 whitespace. I don't think this is a big problem, really.
780 command does something unhelpful if message and signature are sent to
789 Mark Wooding, <mdw@distorted.org.uk>
projects / u / mdw / catacomb / blob