22 \h'-\w'\\$1\ 'u'\\$1\ \c
27 .TH dsig 1 "30 September 2004" "Straylight/Edgeware" "Catacomb cryptographic library"
29 dsig \- compute and verify signatures on collections of files
69 command signs and verifies signatures on a collection of files. It
70 provides a number of subcommands, by which the various operations may be
73 Before the command name,
75 may be given. The following global options are supported:
77 .BR "\-h, \-\-help " [ \fIcommand ...]
78 Writes a brief summary of
80 various options to standard output, and returns a successful exit
81 status. With command names, gives help on those commands.
84 Writes the program's version number to standard output, and returns a
85 successful exit status.
88 Writes a very terse command line summary to standard output, and returns
89 a successful exit status.
91 .BI "\-k, \-\-keyring " file
92 Names the keyring file which
94 is to process. The default keyring, used if this option doesn't specify
95 one, is the file named
97 in the current directory. See
101 for more details about keyring files.
111 attribute is present on the key, then it must have this form; otherwise,
112 the key's type must have the form
115 Algorithm selections are taken from appropriately-named attributes, or,
116 failing that, from the
119 The signature algorithm is chosen according to the setting of
123 for a list of supported signature algorithms.
126 This is almost the same as the RSASSA-PKCS1-v1_5 algorithm described in
127 RFC3447; the difference is that the hash is left bare rather than being
128 wrapped in a DER-encoded
130 structure. This doesn't affect security since the key can only be used
131 with the one hash function anyway, and dropping the DER wrapping permits
132 rapid adoption of new hash functions. Regardless, use of this algorithm
133 is not recommended, since the padding method has been shown vulnerable
143 This is the RSASSA-PSS algorithm described in RFC3447. It is the
144 preferred RSA-based signature scheme. Use the
153 This is the DSA algorithm described in FIPS180-1 and FIPS180-2. Use the
162 This is the ECDSA algorithm described in ANSI X9.62 and FIPS180-2. Use
172 This is the revised KCDSA (Korean Certificate-based Digital Signature
173 Algorithm) described in
174 .I The Revised Version of KCDSA
175 .RB ( http://dasan.sejong.ac.kr/~chlim/pub/kcdsa1.ps ).
187 This is an unofficial elliptic-curve analogue of the KCDSA algorithm.
196 As well as the signature algorithm itself, a hash function is used.
197 This is taken from the
199 attribute on the key, or, failing that, from the
203 or, if that is absent, determined by the signature algorithm as follows.
211 the default hash function is
218 the default hash function is
223 for a list of supported hash functions.
224 .SH "COMMAND REFERENCE"
228 command behaves exactly as the
230 option. With no arguments, it shows an overview of
232 options; with arguments, it describes the named subcommands.
236 command prints various lists of tokens understood by
238 With no arguments, it prints all of the lists; with arguments, it prints
239 just the named lists, in order. The recognized lists can be enumerated
244 command. The lists are as follows.
247 The lists which can be enumerated by the
252 The signature algorithms which can be used in a key's
257 The hash functions which can be used in a key's
263 command creates a signature for a collection of files. The default
264 behaviour is to read a list of whitespace-separated file names (see
265 below for the precise format) from standard input and write the
266 an output file, containing hashes of the files and a digital signature
269 in the current keyring, to standard output, in plain text with binary
270 values Base64-encoded. It is intended to be used in conjunction with
272 This behaviour can be modified by specifying command-line options.
275 Read null-terminated filenames, rather than whitespace-separated names.
276 This is the recommended mode of operation if you have a
278 which understands the
283 Produce output in raw binary rather than the textual output. This isn't
284 a useful thing to do unless you're trying to debug
287 .B "\-v, \-\-verbose"
290 more verbose. At present, this just means that it'll print the hashes
291 of files that it comes across in hex. (Use
293 if this is the output you actually wanted.)
300 .BI "\-c, \-\-comment " string
303 as a comment in the output file. The comment's integrity is protected
306 .BI "\-p, \-\-progress"
307 Write a progress meter to standard error while processing large files.
309 .BI "\-f, \-\-file " name
312 instead of from standard input.
314 .BI "\-h, \-\-hashes " name
315 Rather than hashing files, read precomputed hashes from the file
317 which should be in the format produced by
320 .BI "\-o, \-\-output " name
323 instead of to standard output.
325 .BI "\-k, \-\-key " tag
328 rather than the default
331 .BI "\-e, \-\-expire " date
332 Set the signature to expire at
334 The default is to expire 28 days from creation. Use
336 to make the signature not expire.
338 .B "\-C, \-\-nocheck"
339 Don't check the private key for validity. This makes signing go much
340 faster, but at the risk of using a duff key, and potentially leaking
341 information about the private key.
343 The whitespace-separated format for filenames allows quoting and
344 escaping of strange characters. The backslash
346 can be used to escape whitespace, quotes, or other special characters
347 (including itself), and to represent special characters using the
348 standard C escape sequences
356 A filename can be quoted in
361 Whitespace within quotes is part of the filename. The quotes must be at
362 the beginning and end of the name.
366 command will verify signatures made by the
368 command. With no arguments, it expects to read a text-format signature
369 file from standard input; with an argument, it examines the file it
370 names to see whether it's text or binary.
372 Command-line options provided are:
374 .B "\-v, \-\-verbose"
375 Produce more informational output. The default verbosity level is 1.
378 Produce less information output.
380 .BI "\-p, \-\-progress"
381 Write a progress meter to standard error while processing large files.
383 .B "\-C, \-\-nocheck"
384 Don't check the public key for validity. This makes verification go
385 much faster, but at the risk of using a duff key, and potentially
386 accepting false signatures.
388 Output is written to standard output in a machine-readable format.
389 Formatting errors cause the program to write a diagnostic to standard
390 error and exit nonzero as usual. Lines begin with a keyword:
393 An error prevented verification.
396 The signature is bad: some file had the wrong hash or the signature is
401 encountered a situation which may or may not invalidate the signature.
404 The signature verified correctly.
407 Any other information.
409 The information written at the various verbosity levels is as follows.
411 No output. Watch the exit status.
413 exits zero if the signature was good.
420 messages are printed.
424 messages are printed describing reasons why the signature verification
427 message is printed showing the signature file's comment if any.
431 messages are shown listing the signing program's identification string,
432 the signing key, the signature and expiry dates, and actual signature
437 messages are printed for each file covered, showing its name and hash.
439 There are two output formats: textual and binary. The hash used in the
440 digital signature is always computed on the
442 version of the data, regardless of the external representation.
444 Within the file, whitespace and comments between strings are ignored. A
445 comment begins with a hash
447 and extends until the next newline.
449 Strings are either quoted or whitespace-delimited. A string may be
455 The end-quote character can be backslash-escaped within the string. An
456 occurrence of the unescaped end-quote character terminates the string.
457 A whitespace-delimited string is terminated by any unescaped whitespace
458 character. The C-language escape sequences
466 are recognized within either kind of string.
468 Blocks within the file consist of sequences of strings. The first
471 \(en a simple string ending in a colon
473 \(en which describes the format of the remaining strings.
475 The file consists of a sequence of blocks, each of which begins with a
476 tag byte. The format of the test of the block depends on the tag.
477 Strings are null-terminated; all integers are in network byte order.
479 A binary file always begins with an ident block, which has a tag of 0.
481 The following block types are known. They must appear in the order
482 given, and except where noted must appear exactly once each.
485 Identification string of the generating program.
487 The signing key's id, as eight hex digits (text) or a 32-bit integer
491 The comment string set with the
495 command. This block need not appear.
498 The date the signature was made. In a text file, this has the form
502 in a binary file, it's a 64-bit integer representing the POSIX time.
505 The expiry time of the signature, expressed as for
507 A non-expiring signature is represented by the string
509 in text files, or all-bits-set in binary.
512 A file hash. In text, this is two strings which are the Base-64-encoded
513 hash and the file name; in binary, this is a 16-bit hash length, the raw
514 hash, and the null-terminated filename. There can be any number of
518 .BR "signature: " (6)
519 The signature. In text, this is the Base-64-encoded signature; in
520 binary, it is a 16-bit length followed by the binary signature.
522 The signature covers the
524 representations of the file's
537 Mark Wooding, <mdw@distorted.org.uk>
projects / u / mdw / catacomb / blob