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diff --git a/doc/faq.raw b/doc/faq.raw new file mode 100644 index 000000000..cbab76b0c --- /dev/null +++ b/doc/faq.raw @@ -0,0 +1,1344 @@ +[$htmltitle=GnuPG FAQ] +[$htmlcharset=<meta http-equiv="content-type" content="text/html; charset=utf-8">] +[$sfaqheader=The GnuPG FAQ says:] +[$sfaqfooter= +The most recent version of the FAQ is available from +<http://www.gnupg.org/> +] +[$usenetheader= +] +[$maintainer=David D. Scribner, <faq 'at' gnupg.org>] +[$hGPGHTTP=http://www.gnupg.org] +[$hGPGFTP=ftp://ftp.gnupg.org] +[$hVERSION=1.2.2] + +[H body bgcolor=#ffffff text=#000000 link=#1f00ff alink=#ff0000 vlink=#9900dd] +[H h1]GnuPG Frequently Asked Questions[H /h1] + + +[H p] +Version: 1.6.3[H br] +Last-Modified: Jul 30, 2003[H br] +Maintained-by: [$maintainer] +[H /p] + + +This is the GnuPG FAQ. The latest HTML version is available +[H a href=[$hGPGHTTP]/documentation/faqs.html]here[H/a]. + +The index is generated automatically, so there may be errors. Not all +questions may be in the section they belong to. Suggestions about how +to improve the structure of this FAQ are welcome. + +Please send additions and corrections to the maintainer. It would be +most convenient if you could provide the answer to be included here +as well. Your help is very much appreciated! + +Please, don't send message like "This should be a FAQ - what's the +answer?". If it hasn't been asked before, it isn't a FAQ. In that case +you could search in the mailing list archive. + +[H hr] +<C> +[H hr] + + +<S> GENERAL + +<Q> What is GnuPG? + + [H a href=[$hGPGHTTP]]GnuPG[H /a] stands for GNU Privacy Guard and + is GNU's tool for secure communication and data storage. It can be + used to encrypt data and to create digital signatures. It includes + an advanced key management facility and is compliant with the + proposed OpenPGP Internet standard as described in [H a href=http://www.rfc-editor.org/]RFC 2440[H/a]. + As such, it is aimed to be compatible with PGP from PGP Corp. and + other OpenPGP tools + +<Q> Is GnuPG compatible with PGP? + + In general, yes. GnuPG and newer PGP releases should be implementing + the OpenPGP standard. But there are some interoperability problems. + See question <Rcompat> for details. + +<Q> Is GnuPG free to use for personal or commercial use? + + Yes. GnuPG is part of the GNU family of tools and applications built + and provided in accordance with the Free Software Foundation (FSF) + General Public License (GPL). Therefore the software is free to copy, + use, modify and distribute in accordance with that license. Please + read the file titled COPYING that accompanies the application for + more information. + +<Q> What conventions are used in this FAQ? + + Although GnuPG is being developed for several operating systems + (often in parallel), the conventions used in this FAQ reflect a + UNIX shell environment. For Win32 users, references to a shell + prompt (`$') should be interpreted as a command prompt (`>'), + directory names separated by a forward slash (`/') may need to be + converted to a back slash (`\'), and a tilde (`~') represents a + user's "home" directory (reference question <Rhomedir> for an example). + + Some command-lines presented in this FAQ are too long to properly + display in some browsers for the web page version of this file, and + have been split into two or more lines. For these commands please + remember to enter the entire command-string on one line or the + command will error, or at minimum not give the desired results. + + Please keep in mind that this FAQ contains information that may not + apply to your particular version, as new features and bug fixes are + added on a continuing basis (reference the NEWS file included with + the source or package for noteworthy changes between versions). One + item to note is that starting with GnuPG version 1.1.92 the file + containing user options and settings has been renamed from "options" + to "gpg.conf". Information in the FAQ that relates to the options + file may be interchangable with the newer gpg.conf file in many + instances. See question <Roptions> for details. + + +<S> SOURCES of INFORMATION + +<Q> Where can I find more information on GnuPG? + + On-line resources: + + [H ul] + [H li]The documentation page is located at [H a href=[$hGPGHTTP]/documentation/]<[$hGPGHTTP]/documentation/>[H/a]. + Also, have a look at the HOWTOs and the GNU Privacy Handbook (GPH, + available in English, Spanish and Russian). The latter provides a + detailed user's guide to GnuPG. You'll also find a document about how + to convert from PGP 2.x to GnuPG. + + [H li]At [H a href=[$hGPGHTTP]/documentation/mailing-lists.html]<[$hGPGHTTP]/documentation/mailing-lists.html>[H/a] you'll find + an online archive of the GnuPG mailing lists. Most interesting should + be gnupg-users for all user-related issues and gnupg-devel if you want + to get in touch with the developers. + + In addition, searchable archives can be found on MARC, e.g.: [H br] + gnupg-users: [H a href=http://marc.theaimsgroup.com/?l=gnupg-users&r=1&w=2]<http://marc.theaimsgroup.com/?l=gnupg-users&r=1&w=2>[H/a][H br] + gnupg-devel: [H a href=http://marc.theaimsgroup.com/?l=gnupg-devel&r=1&w=2]<http://marc.theaimsgroup.com/?l=gnupg-devel&r=1&w=2>[H/a][H br] + + [H b]PLEASE:[H /b] + Before posting to a list, read this FAQ and the available documentation. + In addition, search the list archive - maybe your question has already + been discussed. This way you help people focus on topics that have not + yet been resolved. + + [H li]The GnuPG source distribution contains a subdirectory: + + [H samp] + ./doc + [H /samp] + + where some additional documentation is located (mainly interesting + for hackers, not the casual user). + [H /ul] + +<Q> Where do I get GnuPG? + + You can download the GNU Privacy Guard from its primary FTP server + [H a href=[$hGPGFTP]/gcrypt/]<[$hGPGFTP]/gcrypt/>[H /a] or from one of the mirrors: + + [H a href=[$hGPGHTTP]/download/mirrors.html] + <[$hGPGHTTP]/download/mirrors.html> + [H /a] + + The current stable version is [$hVERSION]. Please upgrade to this version as + it includes additional features, functions and security fixes that may + not have existed in prior versions. + + +<S> INSTALLATION + +<Q> Which OSes does GnuPG run on? + + It should run on most Unices as well as Windows versions (including + Windows NT/2000) and Macintosh OS/X. A list of OSes reported to be OK + is presented at: + + [H a href=[$hGPGHTTP]/download/supported_systems.html] + <[$hGPGHTTP]/download/supported_systems.html> + [H /a] + +<Q> Which random data gatherer should I use? + + "Good" random numbers are crucial for the security of your encryption. + Different operating systems provide a variety of more or less quality + random data. Linux and *BSD provide kernel generated random data + through /dev/random - this should be the preferred choice on these + systems. Also Solaris users with the SUNWski package installed have + a /dev/random. In these cases, use the configure option: + + [H samp] + --enable-static-rnd=linux + [H /samp] + + In addition, there's also the kernel random device by Andi Maier + [H a href= http://www.cosy.sbg.ac.at/~andi/SUNrand/]<http://www.cosy.sbg.ac.at/~andi/SUNrand/>[H /a], but it's still beta. Use at your + own risk! + + On other systems, the Entropy Gathering Daemon (EGD) is a good choice. + It is a perl-daemon that monitors system activity and hashes it into + random data. See the download page [H a href=[$hGPGHTTP]/download/]<[$hGPGHTTP]/download/>[H /a] + to obtain EGD. Use: + + [H samp] + --enable-static-rnd=egd + [H /samp] + + here. + + If the above options do not work, you can use the random number + generator "unix". This is [H B]very[H /B] slow and should be avoided. The + random quality isn't very good so don't use it on sensitive data. + +<Didea> +<Q> How do I include support for RSA and IDEA? + + RSA is included as of GnuPG version 1.0.3. + + The official GnuPG distribution does not contain IDEA due to a patent + restriction. The patent does not expire before 2007 so don't expect + official support before then. + + However, there is an unofficial module to include it even in earlier + versions of GnuPG. It's available from + [H a href=ftp://ftp.gnupg.dk/pub/contrib-dk/]<ftp://ftp.gnupg.dk/pub/contrib-dk/>[H /a]. Look for: + + [H pre] + idea.c.gz (c module) + idea.c.gz.sig (signature file) + [H /pre] + + [H pre] + ideadll.zip (c module and win32 dll) + ideadll.zip.sig (signature file) + [H /pre] + + Compilation directives are in the headers of these files. You will + then need to add the following line to your ~/.gnupg/gpg.conf or + ~/.gnupg/options file: + + [H samp] + load-extension idea + [H /samp] + + +<S> USAGE + +<Q> What is the recommended key size? + + 1024 bit for DSA signatures; even for plain Elgamal signatures. + This is sufficient as the size of the hash is probably the weakest + link if the key size is larger than 1024 bits. Encryption keys may + have greater sizes, but you should then check the fingerprint of + this key: + + [H samp] + $ gpg --fingerprint <user ID> + [H /samp] + + As for the key algorithms, you should stick with the default (i.e., + DSA signature and Elgamal encryption). An Elgamal signing key has + the following disadvantages: the signature is larger, it is hard + to create such a key useful for signatures which can withstand some + real world attacks, you don't get any extra security compared to + DSA, and there might be compatibility problems with certain PGP + versions. It has only been introduced because at the time it was + not clear whether there was a patent on DSA. + +<Q> Why does it sometimes take so long to create keys? + + The problem here is that we need a lot of random bytes and for that + we (on Linux the /dev/random device) must collect some random data. + It is really not easy to fill the Linux internal entropy buffer; I + talked to Ted Ts'o and he commented that the best way to fill the + buffer is to play with your keyboard. Good security has its price. + What I do is to hit several times on the shift, control, alternate, + and caps lock keys, because these keys do not produce output to the + screen. This way you get your keys really fast (it's the same thing + PGP2 does). + + Another problem might be another program which eats up your random + bytes (a program (look at your daemons) that reads from /dev/random). + +<Q> And it really takes long when I work on a remote system. Why? + + Don't do this at all! You should never create keys or even use GnuPG + on a remote system because you normally have no physical control + over your secret key ring (which is in most cases vulnerable to + advanced dictionary attacks) - I strongly encourage everyone to only + create keys on a local computer (a disconnected laptop is probably + the best choice) and if you need it on your connected box (I know, + we all do this) be sure to have a strong password for both your + account and for your secret key, and that you can trust your system + administrator. + + When I check GnuPG on a remote system via ssh (I have no Alpha here) + ;-) I have the same problem. It takes a *very* long time to create + the keys, so I use a special option, --quick-random, to generate + insecure keys which are only good for some tests. + +<Q> What is the difference between options and commands? + + If you do a 'gpg --help', you will get two separate lists. The first + is a list of commands. The second is a list of options. Whenever you + run GPG, you [H b]must[H /b] pick exactly one command (with one exception, + see below). You [H b]may[H /b] pick one or more options. The command should, + just by convention, come at the end of the argument list, after all + the options. If the command takes a file (all the basic ones do), + the filename comes at the very end. So the basic way to run gpg is: + + [H samp] + $ gpg [--option something] [--option2] [--option3 something] --command file + [H /samp] + + Some options take arguments. For example, the --output option (which + can be abbreviated as -o) is an option that takes a filename. The + option's argument must follow immediately after the option itself, + otherwise gpg doesn't know which option the argument is supposed to + paired with. As an option, --output and its filename must come before + the command. The --recipient (-r) option takes a name or keyID to + encrypt the message to, which must come right after the -r option. + The --encrypt (or -e) command comes after all the options and is + followed by the file you wish to encrypt. Therefore in this example + the command-line issued would be: + + [H samp] + $ gpg -r alice -o secret.txt -e test.txt + [H /samp] + + If you write the options out in full, it is easier to read: + + [H samp] + $ gpg --recipient alice --output secret.txt --encrypt test.txt + [H /samp] + + If you're encrypting to a file with the extension ".txt", then you'd + probably expect to see ASCII-armored text in the file (not binary), + so you need to add the --armor (-a) option, which doesn't take any + arguments: + + [H samp] + $ gpg --armor --recipient alice --output secret.txt --encrypt test.txt + [H /samp] + + If you imagine square brackets around the optional parts, it becomes + a bit clearer: + + [H samp] + $ gpg [--armor] [--recipient alice] [--output secret.txt] --encrypt test.txt + [H /samp] + + The optional parts can be rearranged any way you want: + + [H samp] + $ gpg --output secret.txt --recipient alice --armor --encrypt test.txt + [H /samp] + + If your filename begins with a hyphen (e.g. "-a.txt"), GnuPG assumes + this is an option and may complain. To avoid this you have to either + use "./-a.txt", or stop the option and command processing with two + hyphens: "-- -a.txt". + + [H B]The exception to using only one command:[H /B] signing and encrypting + at the same time. For this you can combine both commands, such as in: + + [H samp] + $ gpg [--options] --sign --encrypt foo.txt + [H /samp] + +<Q> I can't delete a user ID on my secret keyring because it has + already been deleted on my public keyring. What can I do? + + Because you can only select from the public key ring, there is no + direct way to do this. However it is not very complicated to do + anyway. Create a new user ID with exactly the same name and you + will see that there are now two identical user IDs on the secret + ring. Now select this user ID and delete it. Both user IDs will be + removed from the secret ring. + +<Q> I can't delete my secret key because the public key disappeared. + What can I do? + + To select a key a search is always done on the public keyring, + therefore it is not possible to select a secret key without + having the public key. Normally it should never happen that the + public key got lost but the secret key is still available. The + reality is different, so GnuPG implements a special way to deal + with it: Simply use the long keyID to specify the key to delete, + which can be obtained by using the --with-colons options (it is + the fifth field in the lines beginning with "sec"). + + If you've lost your public key and need to recreate it instead + for continued use with your secret key, you may be able to use + gpgsplit as detailed in question <Rgpgsplit>. + +<Q> What are trust, validity and ownertrust? + + With GnuPG, the term "ownertrust" is used instead of "trust" to + help clarify that this is the value you have assigned to a key + to express how much you trust the owner of this key to correctly + sign (and thereby introduce) other keys. The "validity", or + calculated trust, is a value which indicates how much GnuPG + considers a key as being valid (that it really belongs to the + one who claims to be the owner of the key). For more information + on trust values see the chapter "The Web of Trust" in The GNU + Privacy Handbook. + +<Q> How do I sign a patch file? + + Use "gpg --clearsign --not-dash-escaped ...". The problem with + --clearsign is that all lines starting with a dash are quoted with + "- "; obviously diff produces many lines starting with a dash and + these are then quoted and that is not good for a patch ;-). To use + a patch file without removing the cleartext signature, the special + option --not-dash-escaped may be used to suppress generation of + these escape sequences. You should not mail such a patch because + spaces and line endings are also subject to the signature and a + mailer may not preserve these. If you want to mail a file you can + simply sign it using your MUA (Mail User Agent). + +<Q> Where is the "encrypt-to-self" option? + + Use "--encrypt-to your_keyID". You can use more than one of these + options. To temporarily override the use of this additional key, + you can use the option "--no-encrypt-to". + +<Q> How can I get rid of the Version and Comment headers in armored + messages? + + Use "--no-version --comment ''". Note that the left over blank line + is required by the protocol. + +<Q> What does the "You are using the xxxx character set." mean? + + This note is printed when UTF-8 mapping has to be done. Make sure + that the displayed character set is the one you have activated on + your system. Since "iso-8859-1" is the character set most used, + this is the default. You can change the charset with the option + "--charset". It is important that your active character set matches + the one displayed - if not, restrict yourself to plain 7 bit ASCII + and no mapping has to be done. + +<Q> How can I get list of key IDs used to encrypt a message? + + [H samp] + $ gpg --batch --decrypt --list-only --status-fd 1 2>/dev/null | + awk '/^\[GNUPG:\] ENC_TO / { print $3 }' + [H /samp] + +<Q> Why can't I decrypt files encrypted as symmetrical-only (-c) with + a version of GnuPG prior to 1.0.1. + + There was a bug in GnuPG versions prior to 1.0.1 which affected files + only if 3DES or Twofish was used for symmetric-only encryption (this has + never been the default). The bug has been fixed, but to enable decryption + of old files you should run gpg with the option "--emulate-3des-s2k-bug", + decrypt the file and encrypt it again without this option. + + NOTE: This option was removed in GnuPG development version 1.1.0 and later + updates, so you will need to use a version between 1.0.1 and 1.0.7 to + re-encrypt any affected files. + +<Q> How can I use GnuPG in an automated environment? + + You should use the option --batch and don't use passphrases as + there is usually no way to store it more securely than on the + secret keyring itself. The suggested way to create keys for an + automated environment is: + + On a secure machine: + [H ol] + [H li] If you want to do automatic signing, create a signing subkey + for your key (use the interactive key editing menu by issueing + the command 'gpg --edit-key keyID', enter "addkey" and select + the DSA key type). + [H li] Make sure that you use a passphrase (needed by the current + implementation). + [H li] gpg --export-secret-subkeys --no-comment foo >secring.auto + [H li] Copy secring.auto and the public keyring to a test directory. + [H li] Change to this directory. + [H li] gpg --homedir . --edit foo and use "passwd" to remove the + passphrase from the subkeys. You may also want to remove all + unused subkeys. + [H li] Copy secring.auto to a floppy and carry it to the target box. + [H /ol] + + On the target machine: + [H ol] + [H li] Install secring.auto as the secret keyring. + [H li] Now you can start your new service. It's also a good idea to + install an intrusion detection system so that you hopefully + get a notice of an successful intrusion, so that you in turn + can revoke all the subkeys installed on that machine and + install new subkeys. + [H /ol] + +<Q> Which email-client can I use with GnuPG? + + Using GnuPG to encrypt email is one of the most popular uses. + Several mail clients or mail user agents (MUAs) support GnuPG to + varying degrees. Simplifying a bit, there are two ways mail can be + encrypted with GnuPG: the "old style" ASCII armor (i.e. cleartext + encryption), and RFC 2015 style (previously PGP/MIME, now OpenPGP). + The latter has full MIME support. Some MUAs support only one of + them, so whichever you actually use depends on your needs as well + as the capabilities of your addressee. As well, support may be + native to the MUA, or provided via "plug-ins" or external tools. + + The following list is not exhaustive: + + [H pre] + MUA OpenPGP ASCII How? (N,P,T) + ------------------------------------------------------------- + Calypso N Y P (Unixmail) + Elm N Y T (mailpgp,morepgp) + Elm ME+ N Y N + Emacs/Gnus Y Y T (Mailcrypt,gpg.el) + Emacs/Mew Y Y N + Emacs/VM N Y T (Mailcrypt) + Evolution Y Y N + Exmh Y Y N + GNUMail.app Y Y P (PGPBundle) + GPGMail Y Y N + KMail (<=1.4.x) N Y N + KMail (1.5.x) Y(P) Y(N) P/N + Mozilla Y Y P (Enigmail) + Mulberry Y Y P + Mutt Y Y N + Sylpheed Y Y N + Sylpheed-claws Y Y N + TkRat Y Y N + XEmacs/Gnus Y Y T (Mailcrypt) + XEmacs/Mew Y Y N + XEmacs/VM N Y T (Mailcrypt) + XFmail Y Y N + + N - Native, P - Plug-in, T - External Tool + [H /pre] + + The following table lists proprietary MUAs. The GNU Project + suggests against the use of these programs, but they are listed + for interoperability reasons for your convenience. + + [H pre] + MUA OpenPGP ASCII How? (N,P,T) + ------------------------------------------------------------- + Apple Mail Y Y P (GPGMail) + Becky2 Y Y P (BkGnuPG) + Eudora Y Y P (EuroraGPG) + Eudora Pro Y Y P (EudoraGPG) + Lotus Notes N Y P + Netscape 4.x N Y P + Netscape 7.x Y Y P (Enigmail) + Novell Groupwise N Y P + Outlook N Y P (G-Data) + Outlook Express N Y P (GPGOE) + Pegasus N Y P (QDPGP,PM-PGP) + Pine N Y T (pgpenvelope,(gpg|pgp)4pine) + Postme N Y P (GPGPPL) + The Bat! N Y P (Ritlabs) + [H /pre] + + Good overviews of OpenPGP-support can be found at:[H br] + [H a href=http://www.openpgp.fr.st/courrier_en.html]<http://www.openpgp.fr.st/courrier_en.html>[H /a] and[H br] + [H a href=http://www.bretschneidernet.de/tips/secmua.html]<http://www.bretschneidernet.de/tips/secmua.html>[H /a]. + + Users of Win32 MUAs that lack OpenPGP support may look into + using GPGrelay [H a href=http://gpgrelay.sourceforge.net]<http://gpgrelay.sourceforge.net>[H /a], a small + email-relaying server that uses GnuPG to enable many email clients + to send and receive emails that conform to PGP-MIME (RFC 2015). + +<Q> Can't we have a gpg library? + + This has been frequently requested. However, the current viewpoint + of the GnuPG maintainers is that this would lead to several security + issues and will therefore not be implemented in the foreseeable + future. However, for some areas of application gpgme could do the + trick. You'll find it at [H a href=[$hGPGFTP]/gcrypt/alpha/gpgme]<[$hGPGFTP]/gcrypt/alpha/gpgme>[H /a]. + +<Q> I have successfully generated a revocation certificate, but I don't + understand how to send it to the key servers. + + Most keyservers don't accept a 'bare' revocation certificate. You + have to import the certificate into gpg first: + + [H samp] + $ gpg --import my-revocation.asc + [H /samp] + + then send the revoked key to the keyservers: + + [H samp] + $ gpg --keyserver certserver.pgp.com --send-keys mykeyid + [H /samp] + + (or use a keyserver web interface for this). + +<Dhomedir> +<Q> How do I put my keyring in a different directory? + + GnuPG keeps several files in a special homedir directory. These + include the options file, pubring.gpg, secring.gpg, trustdb.gpg, + and others. GnuPG will always create and use these files. On unices, + the homedir is usually ~/.gnupg; on Windows "C:\gnupg\". + + If you want to put your keyrings somewhere else, use the option: + + [H samp] + --homedir /my/path/ + [H /samp] + + to make GnuPG create all its files in that directory. Your keyring + will be "/my/path/pubring.gpg". This way you can store your secrets + on a floppy disk. Don't use "--keyring" as its purpose is to specify + additional keyring files. + +<Q> How do I verify signed packages? + + Before you can verify the signature that accompanies a package, + you must first have the vendor, organisation, or issueing person's + key imported into your public keyring. To prevent GnuPG warning + messages the key should also be validated (or locally signed). + + You will also need to download the detached signature file along + with the package. These files will usually have the same name as + the package, with either a binary (.sig) or ASCII armor (.asc) + extension. + + Once their key has been imported, and the package and accompanying + signature files have been downloaded, use: + + [H samp] + $ gpg --verify sigfile signed-file + [H /samp] + + If the signature file has the same base name as the package file, + the package can also be verified by specifying just the signature + file, as GnuPG will derive the package's file name from the name + given (less the .sig or .asc extension). For example, to verify a + package named foobar.tar.gz against its detached binary signature + file, use: + + [H samp] + $ gpg --verify foobar.tar.gz.sig + [H /samp] + +<Q> How do I export a keyring with only selected signatures (keys)? + + If you're wanting to create a keyring with only a subset of keys + selected from a master keyring (for a club, user group, or company + department for example), simply specify the keys you want to export: + + [H samp] + $ gpg --armor --export key1 key2 key3 key4 > keys1-4.asc + [H /samp] + +<Dgpgsplit> +<Q> I still have my secret key, but lost my public key. What can I do? + + All OpenPGP secret keys have a copy of the public key inside them, + and in a worst-case scenario, you can create yourself a new public + key using the secret key. + + A tool to convert a secret key into a public one has been included + (it's actually a new option for gpgsplit) and is available with GnuPG + versions 1.2.1 or later (or can be found in CVS). It works like this: + + [H samp] + $ gpgsplit --no-split --secret-to-public secret.gpg >publickey.gpg + [H /samp] + + One should first try to export the secret key and convert just this + one. Using the entire secret keyring should work too. After this has + been done, the publickey.gpg file can be imported into GnuPG as usual. + +<Q> Clearsigned messages sent from my web-mail account have an invalid + signature. Why? + + Check to make sure the settings for your web-based email account + do not use HTML formatting for the pasted clearsigned message. This can + alter the message with embedded HTML markup tags or spaces, resulting + in an invalid signature. The recipient may be able to copy the signed + message block to a text file for verification, or the web email + service may allow you to attach the clearsigned message as a file + if plaintext messages are not an option. + + +<S> COMPATIBILITY ISSUES + +<Dcompat> +<Q> How can I encrypt a message with GnuPG so that PGP is able to decrypt it? + + It depends on the PGP version. + + [H ul] + [H li]PGP 2.x[H br] + You can't do that because PGP 2.x normally uses IDEA which is not + supported by GnuPG as it is patented (see <Ridea>), but if you have a + modified version of PGP you can try this: + + [H samp] + $ gpg --rfc1991 --cipher-algo 3des ... + [H /samp] + + Please don't pipe the data to encrypt to gpg but provide it using a + filename; otherwise, PGP 2 will not be able to handle it. + + As for conventional encryption, you can't do this for PGP 2. + + [H li]PGP 5.x and higher[H br] + You need to provide two additional options: + + [H samp] + --compress-algo 1 --cipher-algo cast5 + [H /samp] + + You may also use "3des" instead of "cast5", and "blowfish" does not + work with all versions of PGP 5. You may also want to put: + + [H samp] + compress-algo 1 + [H /samp] + + into your ~/.gnupg/options file - this does not affect normal GnuPG + operation. + + This applies to conventional encryption as well. + [H /UL] + +<Q> How do I migrate from PGP 2.x to GnuPG? + + PGP 2 uses the RSA and IDEA encryption algorithms. Whereas the RSA + patent has expired and RSA is included as of GnuPG 1.0.3, the IDEA + algorithm is still patented until 2007. Under certain conditions you + may use IDEA even today. In that case, you may refer to Question + <Ridea> about how to add IDEA support to GnuPG and read + [H a href=[$hGPGHTTP]/gph/en/pgp2x.html]<[$hGPGHTTP]/gph/en/pgp2x.html>[H /a] to perform the migration. + +<Q> (removed) + + (empty) + +<Q> Why is PGP 5.x not able to encrypt messages with some keys? + + PGP, Inc. refuses to accept Elgamal keys of type 20 even for + encryption. They only support type 16 (which is identical at least + for decryption). To be more inter-operable, GnuPG (starting with + version 0.3.3) now also uses type 16 for the Elgamal subkey which is + created if the default key algorithm is chosen. You may add a type + 16 Elgamal key to your public key, which is easy as your key + signatures are still valid. + +<Q> Why is PGP 5.x not able to verify my messages? + + PGP 5.x does not accept v4 signatures for data material but OpenPGP + requests generation of v4 signatures for all kind of data, that's why + GnuPG defaults to them. Use the option "--force-v3-sigs" to generate + v3 signatures for data. + +<Q> How do I transfer owner trust values from PGP to GnuPG? + + There is a script in the tools directory to help you. After you have + imported the PGP keyring you can give this command: + + [H samp] + $ lspgpot pgpkeyring | gpg --import-ownertrust + [H /samp] + + where pgpkeyring is the original keyring and not the GnuPG keyring + you might have created in the first step. + +<Q> PGP does not like my secret key. + + Older PGPs probably bail out on some private comment packets used by + GnuPG. These packets are fully in compliance with OpenPGP; however + PGP is not really OpenPGP aware. A workaround is to export the + secret keys with this command: + + [H samp] + $ gpg --export-secret-keys --no-comment -a your-KeyID + [H /samp] + + Another possibility is this: by default, GnuPG encrypts your secret + key using the Blowfish symmetric algorithm. Older PGPs will only + understand 3DES, CAST5, or IDEA symmetric algorithms. Using the + following method you can re-encrypt your secret gpg key with a + different algo: + + [H samp] + $ gpg --s2k-cipher-algo=CAST5 --s2k-digest-algo=SHA1 + --compress-algo=1 --edit-key <username> + [H /samp] + + Then use passwd to change the password (just change it to the same + thing, but it will encrypt the key with CAST5 this time). + + Now you can export it and PGP should be able to handle it. + + For PGP 6.x the following options work to export a key: + + [H samp] + $ gpg --s2k-cipher-algo 3des --compress-algo 1 --rfc1991 + --export-secret-keys <KeyID> + [H /samp] + +<Doptions> +<Q> GnuPG no longer installs a ~/.gnupg/options file. Is it missing? + + No. The ~/.gnupg/options file has been renamed to ~/.gnupg/gpg.conf for + new installs as of version 1.1.92. If an existing ~/.gnupg/options file + is found during an upgrade it will still be used, but this change was + required to have a more consistent naming scheme with forthcoming tools. + An existing options file can be renamed to gpg.conf for users upgrading, + or receiving the message that the "old default options file" is ignored + (occurs if both a gpg.conf and an options file are found). + +<Q> How do you export GnuPG keys for use with PGP? + + This has come up fairly often, so here's the HOWTO: + + PGP can (for most key types) use secret keys generated by GnuPG. The + problems that come up occasionally are generally because GnuPG + supports a few more features from the OpenPGP standard than PGP does. + If your secret key has any of those features in use, then PGP will + reject the key or you will have problems communicating later. Note + that PGP doesn't do Elgamal signing keys at all, so they are not + usable with any version. + + These instructions should work for GnuPG 1.0.7 and later, and PGP + 7.0.3 and later. + + Start by editing the key. Most of this line is not really necessary + as the default values are correct, but it does not hurt to repeat the + values, as this will override them in case you have something else set + in your options file. + + [H samp] + $ gpg --s2k-cipher-algo cast5 --s2k-digest-algo sha1 --s2k-mode 3 + --simple-sk-checksum --edit KeyID + [H /samp] + + Turn off some features. Set the list of preferred ciphers, hashes, + and compression algorithms to things that PGP can handle. (Yes, I + know this is an odd list of ciphers, but this is what PGP itself uses, + minus IDEA). + + [H samp] + > setpref S9 S8 S7 S3 S2 S10 H2 H3 Z1 Z0 + [H /samp] + + Now put the list of preferences onto the key. + + [H samp] + > updpref + [H /samp] + + Finally we must decrypt and re-encrypt the key, making sure that we + encrypt with a cipher that PGP likes. We set this up in the --edit + line above, so now we just need to change the passphrase to make it + take effect. You can use the same passphrase if you like, or take + this opportunity to actually change it. + + [H samp] + > passwd + [H /samp] + + Save our work. + + [H samp] + > save + [H /samp] + + Now we can do the usual export: + + [H samp] + $ gpg --export KeyID > mypublickey.pgp[H br] + $ gpg --export-secret-key KeyID > mysecretkey.pgp + [H /samp] + + Thanks to David Shaw for this information! + + +<S> PROBLEMS and ERROR MESSAGES + +<Q> Why do I get "gpg: Warning: using insecure memory!" + + On many systems this program should be installed as setuid(root). + This is necessary to lock memory pages. Locking memory pages prevents + the operating system from writing them to disk and thereby keeping your + secret keys really secret. If you get no warning message about insecure + memory your operating system supports locking without being root. The + program drops root privileges as soon as locked memory is allocated. + + To setuid(root) permissions on the gpg binary you can either use: + + [H samp] + $ chmod u+s /path/to/gpg + [H /samp] + + or + + [H samp] + $ chmod 4755 /path/to/gpg + [H /samp] + + Some refrain from using setuid(root) unless absolutely required for + security reasons. Please check with your system administrator if you + are not able to make these determinations yourself. + + On UnixWare 2.x and 7.x you should install GnuPG with the 'plock' + privilege to get the same effect: + + [H samp] + $ filepriv -f plock /path/to/gpg + [H /samp] + + If you can't or don't want to install GnuPG setuid(root), you can + use the option "--no-secmem-warning" or put: + + [H samp] + no-secmem-warning + [H /samp] + + in your ~/.gnupg/options or ~/.gnupg/gpg.conf file (this disables + the warning). + + On some systems (e.g., Windows) GnuPG does not lock memory pages + and older GnuPG versions (<=1.0.4) issue the warning: + + [H samp] + gpg: Please note that you don't have secure memory + [H /samp] + + This warning can't be switched off by the above option because it + was thought to be too serious an issue. However, it confused users + too much, so the warning was eventually removed. + +<Q> Large File Support doesn't work ... + + LFS works correctly in post-1.0.4 versions. If configure doesn't + detect it, try a different (i.e., better) compiler. egcs 1.1.2 works + fine, other gccs sometimes don't. BTW, several compilation problems + of GnuPG 1.0.3 and 1.0.4 on HP-UX and Solaris were due to broken LFS + support. + +<Q> In the edit menu the trust values are not displayed correctly after + signing uids. Why? + + This happens because some information is stored immediately in + the trustdb, but the actual trust calculation can be done after the + save command. This is a "not easy to fix" design bug which will be + addressed in some future release. + +<Q> What does "skipping pubkey 1: already loaded" mean? + + As of GnuPG 1.0.3, the RSA algorithm is included. If you still have + a "load-extension rsa" in your options file, the above message + occurs. Just remove the load command from the options file. + +<Q> GnuPG 1.0.4 doesn't create ~/.gnupg ... + + That's a known bug, already fixed in newer versions. + +<Q> An Elgamal signature does not verify anymore since version 1.0.2 ... + + Use the option --emulate-md-encode-bug. + +<Q> Old versions of GnuPG can't verify Elgamal signatures + + Update to GnuPG 1.0.2 or newer. + +<Q> When I use --clearsign, the plain text has sometimes extra dashes + in it - why? + + This is called dash-escaped text and is required by OpenPGP. + It always happens when a line starts with a dash ("-") and is + needed to make the lines that structure signature and text + (i.e., "-----BEGIN PGP SIGNATURE-----") to be the only lines + that start with two dashes. + + If you use GnuPG to process those messages, the extra dashes + are removed. Good mail clients remove those extra dashes when + displaying such a message. + +<Q> What is the thing with "can't handle multiple signatures"? + + Due to different message formats GnuPG is not always able to split + a file with multiple signatures unambiguously into its parts. This + error message informs you that there is something wrong with the input. + + The only way to have multiple signatures in a file is by using the + OpenPGP format with one-pass-signature packets (which is GnuPG's + default) or the cleartext signed format. + +<Q> If I submit a key to a keyserver, nothing happens ... + + You are most likely using GnuPG 1.0.2 or older on Windows. That's + feature isn't yet implemented, but it's a bug not to say it. Newer + versions issue a warning. Upgrade to 1.0.4 or newer. + +<Q> I get "gpg: waiting for lock ..." + + A previous instance of gpg has most likely exited abnormally and left + a lock file. Go to ~/.gnupg and look for .*.lock files and remove them. + +<Q> Older gpg binaries (e.g., 1.0) have problems with keys from newer + gpg binaries ... + + As of 1.0.3, keys generated with gpg are created with preferences to + TWOFISH (and AES since 1.0.4) and that also means that they have the + capability to use the new MDC encryption method. This will go into + OpenPGP soon, and is also suppoted by PGP 7. This new method avoids + a (not so new) attack on all email encryption systems. + + This in turn means that pre-1.0.3 gpg binaries have problems with + newer keys. Because of security and bug fixes, you should keep your + GnuPG installation in a recent state anyway. As a workaround, you can + force gpg to use a previous default cipher algo by putting: + + [H samp] + cipher-algo cast5 + [H /samp] + + into your options file. + +<Q> With 1.0.4, I get "this cipher algorithm is deprecated ..." + + If you just generated a new key and get this message while + encrypting, you've witnessed a bug in 1.0.4. It uses the new AES + cipher Rijndael that is incorrectly being referred as "deprecated". + Ignore this warning, more recent versions of gpg are corrected. + +<Q> Some dates are displayed as ????-??-??. Why? + + Due to constraints in most libc implementations, dates beyond + 2038-01-19 can't be displayed correctly. 64-bit OSes are not + affected by this problem. To avoid printing wrong dates, GnuPG + instead prints some question marks. To see the correct value, you + can use the options --with-colons and --fixed-list-mode. + +<Q> I still have a problem. How do I report a bug? + + Are you sure that it's not been mentioned somewhere on the mailing + lists? Did you have a look at the bug list (you'll find a link to + the list of reported bugs on the documentation page). If you're not + sure about it being a bug, you can send mail to the gnupg-devel + list. Otherwise, use the GUUG bug tracking system + [H a href=http://bugs.guug.de/Reporting.html]<http://bugs.guug.de/Reporting.html>[H /a]. + +<Q> Why doesn't GnuPG support X.509 certificates? + + GnuPG, first and foremost, is an implementation of the OpenPGP + standard (RFC 2440), which is a competing infrastructure, different + from X.509. + + They are both public-key cryptosystems, but how the public keys are + actually handled is different. + +<Q> Why do national characters in my user ID look funny? + + According to OpenPGP, GnuPG encodes user ID strings (and other + things) using UTF-8. In this encoding of Unicode, most national + characters get encoded as two- or three-byte sequences. For + example, å (0xE5 in ISO-8859-1) becomes Ã¥ (0xC3, + 0xA5). This might also be the reason why keyservers can't find + your key. + +<Q> I get 'sed' errors when running ./configure on Mac OS X ... + + This will be fixed after GnuPG has been upgraded to autoconf-2.50. + Until then, find the line setting CDPATH in the configure script + and place an: + + [H samp] + unset CDPATH + [H /samp] + + statement below it. + +<Q> Why does GnuPG 1.0.6 bail out on keyrings used with 1.0.7? + + There is a small bug in 1.0.6 which didn't parse trust packets + correctly. You may want to apply this patch if you can't upgrade: + + [H a href=http://www.gnupg.org/developer/gpg-woody-fix.txt]<http://www.gnupg.org/developer/gpg-woody-fix.txt>[H /a] + +<Q> I upgraded to GnuPG version 1.0.7 and now it takes longer to load my + keyrings. What can I do? + + The way signature states are stored has changed so that v3 signatures + can be supported. You can use the new --rebuild-keydb-caches migration + command, which was built into this release and increases the speed of + many operations for existing keyrings. + +<Q> Doesn't a fully trusted user ID on a key prevent warning messages + when encrypting to other IDs on the key? + + No. That was actually a key validity bug in GnuPG 1.2.1 and earlier + versions. As part of the development of GnuPG 1.2.2, a bug was + discovered in the key validation code. This bug causes keys with + more than one user ID to give all user IDs on the key the amount of + validity given to the most-valid key. The bug has been fixed in GnuPG + release 1.2.2, and upgrading is the recommended fix for this problem. + More information and a patch for a some pre-1.2.2 versions of GnuPG + can be found at: + + [H a href=http://lists.gnupg.org/pipermail/gnupg-announce/2003q2/000268.html]<http://lists.gnupg.org/pipermail/gnupg-announce/2003q2/000268.html>[H /a] + +<Q> I just compiled GnuPG from source on my GNU/Linux RPM-based system + and it's not working. Why? + + Many GNU/Linux distributions that are RPM-based will install a + version of GnuPG as part of its standard installation, placing the + binaries in the /usr/bin directory. Later, compiling and installing + GnuPG from source other than from a source RPM won't normally + overwrite these files, as the default location for placement of + GnuPG binaries is in /usr/local/bin unless the '--prefix' switch + is used during compile to specify an alternate location. Since the + /usr/bin directory more than likely appears in your path before + /usr/local/bin, the older RPM-version binaries will continue to + be used when called since they were not replaced. + + To resolve this, uninstall the RPM-based version with 'rpm -e gnupg' + before installing the binaries compiled from source. If dependency + errors are displayed when attempting to uninstall the RPM (such as + when Red Hat's up2date is also installed, which uses GnuPG), uninstall + the RPM with 'rpm -e gnupg --nodeps' to force the uninstall. Any + dependent files should be automatically replaced during the install + of the compiled version. If the default /usr/local/bin directory is + used, some packages such as SuSE's Yast Online Update may need to be + configured to look for GnuPG binaries in the /usr/local/bin directory, + or symlinks can be created in /usr/bin that point to the binaries + located in /usr/local/bin. + + +<S> ADVANCED TOPICS + +<Q> How does this whole thing work? + + To generate a secret/public keypair, run: + + [H samp] + $ gpg --gen-key + [H /samp] + + and choose the default values. + + Data that is encrypted with a public key can only be decrypted by + the matching secret key. The secret key is protected by a password, + the public key is not. + + So to send your friend a message, you would encrypt your message + with his public key, and he would only be able to decrypt it by + having the secret key and putting in the password to use his secret + key. + + GnuPG is also useful for signing things. Files that are encrypted + with the secret key can be decrypted with the public key. To sign + something, a hash is taken of the data, and then the hash is in some + form encoded with the secret key. If someone has your public key, they + can verify that it is from you and that it hasn't changed by checking + the encoded form of the hash with the public key. + + A keyring is just a large file that stores keys. You have a public + keyring where you store yours and your friend's public keys. You have + a secret keyring that you keep your secret key on, and should be very + careful with. Never ever give anyone else access to it and use a *good* + passphrase to protect the data in it. + + You can 'conventionally' encrypt something by using the option 'gpg -c'. + It is encrypted using a passphrase, and does not use public and secret + keys. If the person you send the data to knows that passphrase, they + can decrypt it. This is usually most useful for encrypting things to + yourself, although you can encrypt things to your own public key in the + same way. It should be used for communication with partners you know + and where it is easy to exchange the passphrases (e.g. with your boy + friend or your wife). The advantage is that you can change the + passphrase from time to time and decrease the risk, that many old + messages may be decrypted by people who accidently got your passphrase. + + You can add and copy keys to and from your keyring with the 'gpg + --import' and 'gpg --export' command. 'gpg --export-secret-keys' will + export secret keys. This is normally not useful, but you can generate + the key on one machine then move it to another machine. + + Keys can be signed under the 'gpg --edit-key' option. When you sign a + key, you are saying that you are certain that the key belongs to the + person it says it comes from. You should be very sure that is really + that person: You should verify the key fingerprint with: + + [H samp] + $ gpg --fingerprint KeyID + [H /samp] + + over the phone (if you really know the voice of the other person), at + a key signing party (which are often held at computer conferences), + or at a meeting of your local GNU/Linux User Group. + + Hmm, what else. You may use the option '-o filename' to force output + to this filename (use '-' to force output to stdout). '-r' just lets + you specify the recipient (which public key you encrypt with) on the + command line instead of typing it interactively. + + Oh yeah, this is important. By default all data is encrypted in some + weird binary format. If you want to have things appear in ASCII text + that is readable, just add the '-a' option. But the preferred method + is to use a MIME aware mail reader (Mutt, Pine and many more). + + There is a small security glitch in the OpenPGP (and therefore GnuPG) + system; to avoid this you should always sign and encrypt a message + instead of only encrypting it. + +<Q> Why are some signatures with an ELG-E key valid? + + These are Elgamal keys generated by GnuPG in v3 (RFC 1991) packets. + The OpenPGP draft later changed the algorithm identifier for Elgamal + keys which are usable for signatures and encryption from 16 to 20. + GnuPG now uses 20 when it generates new Elgamal keys but still + accepts 16 (which is according to OpenPGP "encryption only") if this + key is in a v3 packet. GnuPG is the only program which had used + these v3 Elgamal keys - so this assumption is quite safe. + +<Q> How does the whole trust thing work? + + It works more or less like PGP. The difference is that the trust is + computed at the time it is needed. This is one of the reasons for + the trustdb which holds a list of valid key signatures. If you are + not running in batch mode you will be asked to assign a trust + parameter (ownertrust) to a key. + + You can see the validity (calculated trust value) using this + command. + + [H samp] + $ gpg --list-keys --with-colons + [H /samp] + + If the first field is "pub" or "uid", the second field shows you the + trust: + + [H pre] + o = Unknown (this key is new to the system) + e = The key has expired + q = Undefined (no value assigned) + n = Don't trust this key at all + m = There is marginal trust in this key + f = The key is full trusted + u = The key is ultimately trusted; this is only used + for keys for which the secret key is also available. + r = The key has been revoked + d = The key has been disabled + [H /pre] + + The value in the "pub" record is the best one of all "uid" records. + You can get a list of the assigned trust values (how much you trust + the owner to correctly sign another person's key) with: + + [H samp] + $ gpg --list-ownertrust + [H /samp] + + The first field is the fingerprint of the primary key, the second + field is the assigned value: + + [H pre] + - = No ownertrust value yet assigned or calculated. + n = Never trust this keyholder to correctly verify others signatures. + m = Have marginal trust in the keyholders capability to sign other + keys. + f = Assume that the key holder really knows how to sign keys. + u = No need to trust ourself because we have the secret key. + [H /pre] + + Keep these values confidential because they express your opinions + about others. PGP stores this information with the keyring thus it + is not a good idea to publish a PGP keyring instead of exporting the + keyring. GnuPG stores the trust in the trustdb.gpg file so it is okay + to give a gpg keyring away (but we have a --export command too). + +<Q> What kind of output is this: "key C26EE891.298, uid 09FB: ...."? + + This is the internal representation of a user ID in the trustdb. + "C26EE891" is the keyid, "298" is the local ID (a record number in + the trustdb) and "09FB" is the last two bytes of a ripe-md-160 hash + of the user ID for this key. + +<Q> How do I interpret some of the informational outputs? + + While checking the validity of a key, GnuPG sometimes prints some + information which is prefixed with information about the checked + item. + + [H samp] + "key 12345678.3456" + [H /samp] + + This is about the key with key ID 12345678 and the internal number + 3456, which is the record number of the so called directory record + in the trustdb. + + [H samp] + "uid 12345678.3456/ACDE" + [H /samp] + + This is about the user ID for the same key. To identify the user ID + the last two bytes of a ripe-md-160 over the user ID ring is printed. + + [H samp] + "sig 12345678.3456/ACDE/9A8B7C6D" + [H /samp] + + This is about the signature with key ID 9A8B7C6D for the above key + and user ID, if it is a signature which is direct on a key, the user + ID part is empty (..//..). + +<Q> Are the header lines of a cleartext signature part of the signed + material? + + No. For example you can add or remove "Comment:" lines. They have + a purpose like the mail header lines. However a "Hash:" line is + needed for OpenPGP signatures to tell the parser which hash + algorithm to use. + +<Q> What is the list of preferred algorithms? + + The list of preferred algorithms is a list of cipher, hash and + compression algorithms stored in the self-signature of a key during + key generation. When you encrypt a document, GnuPG uses this list + (which is then part of a public key) to determine which algorithms + to use. Basically it tells other people what algorithms the + recipient is able to handle and provides an order of preference. + +<Q> How do I change the list of preferred algorithms? + + In version 1.0.7 or later, you can use the edit menu and set the + new list of preference using the command "setpref"; the format of + this command resembles the output of the command "pref". The + preference is not changed immediately but the set preference will + be used when a new user ID is created. If you want to update the + preferences for existing user IDs, select those user IDs (or select + none to update all) and enter the command "updpref". Note that the + timestamp of the self-signature is increased by one second when + running this command. + + +<S> ACKNOWLEDGEMENTS + + Many thanks to Nils Ellmenreich for maintaining this FAQ file for + such a long time, Werner Koch for the original FAQ file, and to all + posters to gnupg-users and gnupg-devel. They all provided most of + the answers. + + Also thanks to Casper Dik for providing us with a script to generate + this FAQ (he uses it for the excellent Solaris2 FAQ). + +[H hr] + +Copyright (C) 2000, 2001, 2002, 2003 Free Software Foundation, Inc., +51 Franklin Street, Fifth Floor, Boston, MA 02111, USA + +Verbatim copying and distribution of this entire article is permitted in +any medium, provided this notice is preserved. |