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
67 command signs and verifies signatures on a collection of files. It
68 provides a number of subcommands, by which the various operations may be
71 Before the command name,
73 may be given. The following global options are supported:
75 .BR "\-h, \-\-help " [ \fIcommand ...]
76 Writes a brief summary of
78 various options to standard output, and returns a successful exit
79 status. With command names, gives help on those commands.
82 Writes the program's version number to standard output, and returns a
83 successful exit status.
86 Writes a very terse command line summary to standard output, and returns
87 a successful exit status.
89 .BI "\-k, \-\-keyring " file
90 Names the keyring file which
92 is to process. The default keyring, used if this option doesn't specify
93 one, is the file named
95 in the current directory. See
99 for more details about keyring files.
109 attribute is present on the key, then it must have this form; otherwise,
110 the key's type must have the form
113 Algorithm selections are taken from appropriately-named attributes, or,
114 failing that, from the
117 The signature algorithm is chosen according to the setting of
121 for a list of supported signature algorithms.
124 This is almost the same as the RSASSA-PKCS1-v1_5 algorithm described in
125 RFC3447; the difference is that the hash is left bare rather than being
126 wrapped in a DER-encoded
128 structure. This doesn't affect security since the key can only be used
129 with the one hash function anyway, and dropping the DER wrapping permits
130 rapid adoption of new hash functions. Regardless, use of this algorithm
131 is not recommended, since the padding method has been shown vulnerable
141 This is the RSASSA-PSS algorithm described in RFC3447. It is the
142 preferred RSA-based signature scheme. Use the
151 This is the DSA algorithm described in FIPS180-1 and FIPS180-2. Use the
160 This is the ECDSA algorithm described in ANSI X9.62 and FIPS180-2. Use
170 This is the revised KCDSA (Korean Certificate-based Digital Signature
171 Algorithm) described in
172 .I The Revised Version of KCDSA
173 .RB ( http://dasan.sejong.ac.kr/~chlim/pub/kcdsa1.ps ).
185 This is an unofficial elliptic-curve analogue of the KCDSA algorithm.
194 As well as the signature algorithm itself, a hash function is used.
195 This is taken from the
197 attribute on the key, or, failing that, from the
201 or, if that is absent, determined by the signature algorithm as follows.
209 the default hash function is
216 the default hash function is
221 for a list of supported hash functions.
222 .SH "COMMAND REFERENCE"
226 command behaves exactly as the
228 option. With no arguments, it shows an overview of
230 options; with arguments, it describes the named subcommands.
234 command prints various lists of tokens understood by
236 With no arguments, it prints all of the lists; with arguments, it prints
237 just the named lists, in order. The recognized lists can be enumerated
242 command. The lists are as follows.
245 The lists which can be enumerated by the
250 The signature algorithms which can be used in a key's
255 The hash functions which can be used in a key's
261 command creates a signature for a collection of files. The default
262 behaviour is to read a list of whitespace-separated file names (see
263 below for the precise format) from standard input and write the
264 an output file, containing hashes of the files and a digital signature
267 in the current keyring, to standard output, in plain text with binary
268 values Base64-encoded. It is intended to be used in conjunction with
270 This behaviour can be modified by specifying command-line options.
273 Read null-terminated filenames, rather than whitespace-separated names.
274 This is the recommended mode of operation if you have a
276 which understands the
281 Produce output in raw binary rather than the textual output. This isn't
282 a useful thing to do unless you're trying to debug
285 .B "\-v, \-\-verbose"
288 more verbose. At present, this just means that it'll print the hashes
289 of files that it comes across in hex. (Use
291 if this is the output you actually wanted.)
298 .BI "\-c, \-\-comment " string
301 as a comment in the output file. The comment's integrity is protected
304 .BI "\-p, \-\-progress"
305 Write a progress meter to standard error while processing large files.
307 .BI "\-f, \-\-file " name
310 instead of from standard input.
312 .BI "\-o, \-\-output " name
315 instead of to standard output.
317 .BI "\-k, \-\-key " tag
320 rather than the default
323 .BI "\-e, \-\-expire " date
324 Set the signature to expire at
326 The default is to expire 28 days from creation. Use
328 to make the signature not expire.
330 .B "\-C, \-\-nocheck"
331 Don't check the private key for validity. This makes signing go much
332 faster, but at the risk of using a duff key, and potentially leaking
333 information about the private key.
335 The whitespace-separated format for filenames allows quoting and
336 escaping of strange characters. The backslash
338 can be used to escape whitespace, quotes, or other special characters
339 (including itself), and to represent special characters using the
340 standard C escape sequences
348 A filename can be quoted in
353 Whitespace within quotes is part of the filename. The quotes must be at
354 the beginning and end of the name.
358 command will verify signatures made by the
360 command. With no arguments, it expects to read a text-format signature
361 file from standard input; with an argument, it examines the file it
362 names to see whether it's text or binary.
364 Command-line options provided are:
366 .B "\-v, \-\-verbose"
367 Produce more informational output. The default verbosity level is 1.
370 Produce less information output.
372 .BI "\-p, \-\-progress"
373 Write a progress meter to standard error while processing large files.
375 .B "\-C, \-\-nocheck"
376 Don't check the public key for validity. This makes verification go
377 much faster, but at the risk of using a duff key, and potentially
378 accepting false signatures.
380 Output is written to standard output in a machine-readable format.
381 Formatting errors cause the program to write a diagnostic to standard
382 error and exit nonzero as usual. Lines begin with a keyword:
385 An error prevented verification.
388 The signature is bad: some file had the wrong hash or the signature is
393 encountered a situation which may or may not invalidate the signature.
396 The signature verified correctly.
399 Any other information.
401 The information written at the various verbosity levels is as follows.
403 No output. Watch the exit status.
405 exits zero if the signature was good.
412 messages are printed.
416 messages are printed describing reasons why the signature verification
419 message is printed showing the signature file's comment if any.
423 messages are shown listing the signing program's identification string,
424 the signing key, the signature and expiry dates, and actual signature
429 messages are printed for each file covered, showing its name and hash.
431 There are two output formats: textual and binary. The hash used in the
432 digital signature is always computed on the
434 version of the data, regardless of the external representation.
436 Within the file, whitespace and comments between strings are ignored. A
437 comment begins with a hash
439 and extends until the next newline.
441 Strings are either quoted or whitespace-delimited. A string may be
447 The end-quote character can be backslash-escaped within the string. An
448 occurrence of the unescaped end-quote character terminates the string.
449 A whitespace-delimited string is terminated by any unescaped whitespace
450 character. The C-language escape sequences
458 are recognized within either kind of string.
460 Blocks within the file consist of sequences of strings. The first
463 \(en a simple string ending in a colon
465 \(en which describes the format of the remaining strings.
467 The file consists of a sequence of blocks, each of which begins with a
468 tag byte. The format of the test of the block depends on the tag.
469 Strings are null-terminated; all integers are in network byte order.
471 A binary file always begins with an ident block, which has a tag of 0.
473 The following block types are known. They must appear in the order
474 given, and except where noted must appear exactly once each.
477 Identification string of the generating program.
479 The signing key's id, as eight hex digits (text) or a 32-bit integer
483 The comment string set with the
487 command. This block need not appear.
490 The date the signature was made. In a text file, this has the form
494 in a binary file, it's a 64-bit integer representing the POSIX time.
497 The expiry time of the signature, expressed as for
499 A non-expiring signature is represented by the string
501 in text files, or all-bits-set in binary.
504 A file hash. In text, this is two strings which are the Base-64-encoded
505 hash and the file name; in binary, this is a 16-bit hash length, the raw
506 hash, and the null-terminated filename. There can be any number of
510 .BR "signature: " (6)
511 The signature. In text, this is the Base-64-encoded signature; in
512 binary, it is a 16-bit length followed by the binary signature.
514 The signature covers the
516 representations of the file's
529 Mark Wooding, <mdw@distorted.org.uk>
projects / u / mdw / catacomb / blob