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.
197 This is Bernstein, Duif, Lange, Schwabe, and Yang's Ed25519 algorithm.
198 More specifically, this is HashEd25519
201 algorithm \(en by default
212 As well as the signature algorithm itself, a hash function is used.
213 This is taken from the
215 attribute on the key, or, failing that, from the
219 or, if that is absent, determined by the signature algorithm as follows.
227 the default hash function is
234 the default hash function is
239 for a list of supported hash functions.
240 .SH "COMMAND REFERENCE"
244 command behaves exactly as the
246 option. With no arguments, it shows an overview of
248 options; with arguments, it describes the named subcommands.
252 command prints various lists of tokens understood by
254 With no arguments, it prints all of the lists; with arguments, it prints
255 just the named lists, in order. The recognized lists can be enumerated
260 command. The lists are as follows.
263 The lists which can be enumerated by the
268 The signature algorithms which can be used in a key's
273 The hash functions which can be used in a key's
279 command creates a signature for a collection of files. The default
280 behaviour is to read a list of whitespace-separated file names (see
281 below for the precise format) from standard input and write the
282 an output file, containing hashes of the files and a digital signature
285 in the current keyring, to standard output, in plain text with binary
286 values Base64-encoded. It is intended to be used in conjunction with
288 This behaviour can be modified by specifying command-line options.
291 Read null-terminated filenames, rather than whitespace-separated names.
292 This is the recommended mode of operation if you have a
294 which understands the
299 Produce output in raw binary rather than the textual output. This isn't
300 a useful thing to do unless you're trying to debug
303 .B "\-v, \-\-verbose"
306 more verbose. At present, this just means that it'll print the hashes
307 of files that it comes across in hex. (Use
309 if this is the output you actually wanted.)
316 .BI "\-c, \-\-comment " string
319 as a comment in the output file. The comment's integrity is protected
322 .BI "\-p, \-\-progress"
323 Write a progress meter to standard error while processing large files.
325 .BI "\-f, \-\-file " name
328 instead of from standard input.
330 .BI "\-h, \-\-hashes " name
331 Rather than hashing files, read precomputed hashes from the file
333 which should be in the format produced by
336 .BI "\-o, \-\-output " name
339 instead of to standard output.
341 .BI "\-k, \-\-key " tag
344 rather than the default
347 .BI "\-e, \-\-expire " date
348 Set the signature to expire at
350 The default is to expire 28 days from creation. Use
352 to make the signature not expire.
354 .B "\-C, \-\-nocheck"
355 Don't check the private key for validity. This makes signing go much
356 faster, but at the risk of using a duff key, and potentially leaking
357 information about the private key.
359 The whitespace-separated format for filenames allows quoting and
360 escaping of strange characters. The backslash
362 can be used to escape whitespace, quotes, or other special characters
363 (including itself), and to represent special characters using the
364 standard C escape sequences
372 A filename can be quoted in
377 Whitespace within quotes is part of the filename. The quotes must be at
378 the beginning and end of the name.
382 command will verify signatures made by the
384 command. With no arguments, it expects to read a text-format signature
385 file from standard input; with an argument, it examines the file it
386 names to see whether it's text or binary.
388 Command-line options provided are:
390 .B "\-v, \-\-verbose"
391 Produce more informational output. The default verbosity level is 1.
394 Produce less information output.
397 Report files whose hashes have not been checked.
399 .BI "\-p, \-\-progress"
400 Write a progress meter to standard error while processing large files.
402 .B "\-C, \-\-nocheck"
403 Don't check the public key for validity. This makes verification go
404 much faster, but at the risk of using a duff key, and potentially
405 accepting false signatures.
407 Output is written to standard output in a machine-readable format.
408 Formatting errors cause the program to write a diagnostic to standard
409 error and exit nonzero as usual. Lines begin with a keyword:
412 An error prevented verification.
415 The signature is bad: some file had the wrong hash or the signature is
420 encountered a situation which may or may not invalidate the signature.
423 The signature verified correctly.
425 .BI "JUNK " type " " name
428 was found (as a result of the search requested by the
430 option), but it was not mentioned in the signature file and therefore
431 has not been checked.
434 Any other information.
436 The information written at the various verbosity levels is as follows.
438 No output. Watch the exit status.
440 exits zero if the signature was good.
447 messages are printed.
451 messages are printed describing reasons why the signature verification
454 message is printed showing the signature file's comment if any.
458 messages are shown listing the signing program's identification string,
459 the signing key, the signature and expiry dates, and actual signature
464 messages are printed for each file covered, showing its name and hash.
466 There are two output formats: textual and binary. The hash used in the
467 digital signature is always computed on the
469 version of the data, regardless of the external representation.
471 Within the file, whitespace and comments between strings are ignored. A
472 comment begins with a hash
474 and extends until the next newline.
476 Strings are either quoted or whitespace-delimited. A string may be
482 The end-quote character can be backslash-escaped within the string. An
483 occurrence of the unescaped end-quote character terminates the string.
484 A whitespace-delimited string is terminated by any unescaped whitespace
485 character. The C-language escape sequences
493 are recognized within either kind of string.
495 Blocks within the file consist of sequences of strings. The first
498 \(en a simple string ending in a colon
500 \(en which describes the format of the remaining strings.
502 The file consists of a sequence of blocks, each of which begins with a
503 tag byte. The format of the test of the block depends on the tag.
504 Strings are null-terminated; all integers are in network byte order.
506 A binary file always begins with an ident block, which has a tag of 0.
508 The following block types are known. They must appear in the order
509 given, and except where noted must appear exactly once each.
512 Identification string of the generating program.
514 The signing key's id, as eight hex digits (text) or a 32-bit integer
518 The comment string set with the
522 command. This block need not appear.
525 The date the signature was made. In a text file, this has the form
529 in a binary file, it's a 64-bit integer representing the POSIX time.
532 The expiry time of the signature, expressed as for
534 A non-expiring signature is represented by the string
536 in text files, or all-bits-set in binary.
539 A file hash. In text, this is two strings which are the Base-64-encoded
540 hash and the file name; in binary, this is a 16-bit hash length, the raw
541 hash, and the null-terminated filename. There can be any number of
545 .BR "signature: " (6)
546 The signature. In text, this is the Base-64-encoded signature; in
547 binary, it is a 16-bit length followed by the binary signature.
549 The signature covers the
551 representations of the file's
564 Mark Wooding, <mdw@distorted.org.uk>
~mdw / catacomb / blob