NETPGP(1)               NetBSD General Commands Manual               NETPGP(1)

NAME
     netpgp -- signing, verification, encryption, and decryption utility

SYNOPSIS
     netpgp --encrypt [--output=filename] [options] file ...
     netpgp --decrypt [--output=filename] [--pass-fd=fd]
            [--num-tries=attempts] [options] file ...

     netpgp --sign [--armor] [--detach] [--hash=algorithm] [--output=filename]
            [--pass-fd=fd] [--from=sig-valid-from] [--num-tries=attempts]
            [--duration=sig-valid-duration] [options] file ...
     netpgp --verify [options] file ...
     netpgp --cat [--output=filename] [options] file ...
     netpgp --clearsign [--output=filename] [--pass-fd=fd] [options] file ...
     netpgp --list-packets [--pass-fd=fd] file ...
     netpgp --version
     netpgp [-Vdesv] [-olong-option=value] file ...

            where the long options for all commands are:

            [--cipher=ciphername]
            [--coredumps]
            [--homedir=home-directory]
            [--keyring=keyring]
            [--results=filename]
            [--ssh-keys]
            [--userid=userid]
            [--verbose]

DESCRIPTION
     The netpgp command can digitally sign files and verify that the signa-
     tures attached to files were signed by a given user identifier.  netpgp
     can also encrypt files using the public or private keys of users and, in
     the same manner, decrypt files which were encrypted.

     For signing and encryption, a unique identity is needed.  This identity
     is made up of a private and public key.  The public key part is made
     available and known to everyone.  The private key is kept secret, and
     known only to the user who created the identity.  The secret key is pro-
     tected with a passphrase.

     In rough terms, a digital signature is a digest of a file's contents,
     encrypted with the user's private key.  Since together, the private and
     public keys identify the user uniquely, the signature can be used to
     identify the exact version of the file, and any changes made to the file
     will mean that the signature no longer matches.

     As a corollary, the file can be transformed using a user's public key,
     into text such that the contents can only be viewed by someone with the
     corresponding private key.  This is called encryption.

     To manipulate keys themselves, a separate utility is provided, called
     netpgpkeys(1).

     Keyrings are collections of public keys belonging to other users.  By
     using other means of identification, it is possible to establish the bona
     fides of other users.  Once trust has been established, the public key of
     the other user will be signed.  The other user's public key can be added
     to our keyring.  The other user will add our public key to their keyring.

     Keys can be listed, exported (i.e. made available to others), and
     imported (i.e. users who have signed our public key).

     The --list-packets command can be used for debugging purposes.

     The following commands are used to sign and verify signatures:

     --cat         The signature of the signed file named on the command line
                   is verified against the contents of the file itself.  If
                   the two match, then the original contents are sent to stan-
                   dard out.  If the signature does not match, no output is
                   generated.

     --clearsign   The signature of the file named on the command line is cal-
                   culated in the same manner as the --sign command, but the
                   text is added to the file such that the text itself is not
                   in binary format, but can be read by mere mortals.

     --sign        The private key is used to digitally sign the files named
                   on the command line.  The file and its attached signature
                   are created with a ``.gpg'' extension to the original file
                   name.  The user will be prompted for their pass phrase
                   using getpass(3).

     --verify      For each of the files named on the command line, the signa-
                   ture of the file is verified, checking the contents against
                   the user's public signature.

     The following commands can be used to encrypt and decrypt files:

     --decrypt     Decrypt the file using the user's private key.  The pass
                   phrase will be obtained by prompting the user to type it
                   in, using getpass(3).

     --encrypt     Use the user's public key to encrypt the files named on the
                   command line.

     --list-packets
                   List all the ``packets'' in an encrypted or signed file.
                   Internally, netpgp splits an encrypted or signed file into
                   separate packets, and this option is used to give a verbose
                   representation of these packets on standard output.

     --version     Print the version information from the libnetpgp(3)
                   library.

     In addition to one of the preceding commands, a number of qualifiers or
     options may be given.

     --armour, -armor
                   This option, however it is spelled, wraps the signature as
                   an ASCII-encoded piece of text, for ease of use.

     --cipher ciphername
                   can be used to specify the symmetric encryption algorithm
                   (or cipher) which is used when encrypting data.  To decrypt
                   this data, the same cipher will be needed, so care should
                   be taken at encryption time to make sure that the person
                   who decrypts the data has access to the cipher used.  The
                   default cipher algorithm is the ``CAST5'' algorithm.

     --detached    When signing a file, place the resulting signature in a
                   separate file from the one being signed.

     --hash-alg hash-algorithm
                   can be used to specify the hash algorithm (sometimes called
                   a digest algorithm) which is used with RSA keys when sign-
                   ing text.  The default hash algorithm is the ``SHA256''
                   algorithm.  At the present time, ``SHA1'' may also be used,
                   although it is recommended that SHA256 be used, due to
                   recent advances in generating collisions for the SHA1 hash-
                   ing algorithm.

     --homedir home-directory
                   Keyrings are normally located, for historical reasons,
                   within the user's home directory in a subdirectory called
                   ``.gnupg'' and this option specifies an alternative loca-
                   tion in which to find that sub-directory.

     --keyring keyring
                   This option specifies an alternative keyring to be used.
                   All keyring operations will be relative to this alternative
                   keyring.

     --output      specifies a filename to which verified output from a signed
                   file may be redirected.  The default is to send the veri-
                   fied output to stdout, and this may also be specified using
                   the ``-'' value.

     --results filename
                   specifies a filename to which the results of the operation
                   should be sent.  The default is to send the results to
                   stderr.

     --ssh-keys    specifies that the public and private keys should be taken
                   from the ssh(1) host key files, usually found in
                   /etc/ssh/ssh_host_rsa_key and /etc/ssh/ssh_host_rsa_key.pub
                   for the private and public host keys.

     --userid userid
                   This option specifies the user identity to be used for all
                   operations.  This identity can either be in the form of the
                   full name, or as an email address.  Care should be exer-
                   cised with these ways of specifying the user identity,
                   since the netpgp utility has no way of verifying that an
                   email address is valid, or that a key belongs to a certain
                   individual.  The trust for a signed key is given by the
                   other signers of that key.  The 16 hexadecimal digit user
                   identity should be used when specifying user identities
                   --email addresses and names are provided as aliases.

     --pass-fd=fd  This option is intended for the use of external programs
                   which may like to use the libnetpgp(3) library through the
                   netpgp interface, but have their own ways of retrieving and
                   caching the passphrase for the secret key.  In this case,
                   the netpgp utility will read a line of text from the file
                   descriptor passed to it in the command line argument,
                   rather than using its own methods of retrieving the
                   passphrase from the user.

     --num-tries=attempts
                   This option sets the maximum number of attempts to get the
                   correct passphrase from the user.  A value of unlimited
                   means that there is no maximum number of attempts, and the
                   utility will loop endlessly until the correct passphrase
                   has been entered, or the utility is terminated.

     --from=signature-valid-from
                   This option allows the signer to specify a time as the
                   starting point for validity of the signature.  In this way
                   it is possible to prevent files from being verified until a
                   specific point in time.  The time can be specified either
                   in YYYY-MM-DD format, or as the number of seconds since the
                   epoch.

     --duration=signature-valid-to
                   This option allows the signer to specify a time as the end
                   point for validity of the signature.  In this way it is
                   possible to prevent files from being verified after a spe-
                   cific point in time.  The time can be specified either in
                   YYYY-MM-DD format, or as the number of seconds.

     --verbose     This option can be used to view information during the
                   process of the netpgp requests.

     --coredumps   in normal processing, if an error occurs, the contents of
                   memory are saved to disk, and can be read using tools to
                   analyse behaviour.  Unfortunately this can disclose infor-
                   mation to people viewing the core dump, such as secret
                   keys, and passphrases protecting those keys.  In normal
                   operation, netpgp will turn off the ability to save core
                   dumps on persistent storage, but selecting this option will
                   allow core dumps to be written to disk.  This option should
                   be used wisely, and any core dumps should be deleted in a
                   secure manner when no longer needed.

PASS PHRASES
     At the present time, the pass phrase cannot be changed by netpgpkeys(1)
     once it has been chosen, and will be used for the life of the key, so a
     wise choice is advised.  The pass phrase should not be an easily guess-
     able word or phrase, or related to information that can be gained through
     ``social engineering'' using search engines, or other public information
     retrieval methods.

     getpass(3) will be used to obtain the pass phrase from the user if it is
     needed, such as during signing or encryption, or key generation, so that
     any secret information cannot be viewed by other users using the ps(1) or
     top(1) commands, or by looking over the shoulder at the screen.

     Since the public and private key pair can be used to verify a person's
     identity, and since identity theft can have far-reaching consequences,
     users are strongly encouraged to enter their pass phrases only when
     prompted by the application.

SIGNING AND VERIFICATION
     Signing and verification of a file is best viewed using the following
     example:

     % netpgp --sign --userid=agc@netbsd.org a
     pub 2048/RSA (Encrypt or Sign) 1b68dcfcc0596823 2004-01-12
     Key fingerprint: d415 9deb 336d e4cc cdfa 00cd 1b68 dcfc c059 6823
     uid              Alistair Crooks <agc@netbsd.org>
     uid              Alistair Crooks <agc@pkgsrc.org>
     uid              Alistair Crooks <agc@alistaircrooks.com>
     uid              Alistair Crooks <alistair@hockley-crooks.com>
     netpgp passphrase:
     % netpgp --verify a.gpg
     Good signature for a.gpg made Thu Jan 29 03:06:00 2009
     using RSA (Encrypt or Sign) key 1B68DCFCC0596823
     pub 2048/RSA (Encrypt or Sign) 1b68dcfcc0596823 2004-01-12
     Key fingerprint: d415 9deb 336d e4cc cdfa 00cd 1b68 dcfc c059 6823
     uid              Alistair Crooks <alistair@hockley-crooks.com>
     uid              Alistair Crooks <agc@pkgsrc.org>
     uid              Alistair Crooks <agc@netbsd.org>
     uid              Alistair Crooks <agc@alistaircrooks.com>
     %

     In the example above, a signature is made on a single file called ``a''
     using a user identity corresponding to ``agc@netbsd.org'' The key located
     for the user identity is displayed, and the user is prompted to type in
     their passphrase.  The resulting file, called ``a.gpg'' is placed in the
     same directory.  The second part of the example shows a verification of
     the signed file taking place.  The time and user identity of the signa-
     tory is displayed, followed by a fuller description of the public key of
     the signatory.  In both cases, the exit value from the utility was a suc-
     cessful one.

     If a detached signature of a file called ``a'' is requested, the signa-
     ture would be placed in a file called ``a.sig''.

     To encrypt a file, the user's public key is used.  Subsequent decryption
     of the file requires that the secret key is known.  When decrypting, the
     key is displayed, and the passphrase protecting the secret key must be
     typed in to access the data in the encrypted file.

     % netpgp --encrypt --userid=c0596823 a
     % netpgp --decrypt a.gpg
     pub 2048/RSA (Encrypt or Sign) 1b68dcfcc0596823 2004-01-12
     Key fingerprint: d415 9deb 336d e4cc cdfa 00cd 1b68 dcfc c059 6823
     uid              Alistair Crooks <agc@netbsd.org>
     uid              Alistair Crooks <agc@pkgsrc.org>
     uid              Alistair Crooks <agc@alistaircrooks.com>
     uid              Alistair Crooks <alistair@hockley-crooks.com>
     netpgp passphrase:
     %

     If no file name is provided, the data will be read from standard input,
     and displayed on standard output:

     % netpgp --encrypt < a | netpgp --decrypt > b
     netpgp: default key set to "C0596823"
     netpgp: default key set to "C0596823"
     pub 2048/RSA (Encrypt or Sign) 1b68dcfcc0596823 2004-01-12
     Key fingerprint: d415 9deb 336d e4cc cdfa 00cd 1b68 dcfc c059 6823
     uid              Alistair Crooks <agc@netbsd.org>
     uid              Alistair Crooks <agc@pkgsrc.org>
     uid              Alistair Crooks <agc@alistaircrooks.com>
     uid              Alistair Crooks <alistair@hockley-crooks.com>
     netpgp passphrase:
     %

     This simple (and contrived) example shows that netpgp commands can be
     used together in a pipeline to produce the desired effect.

     % netpgp --sign < a | netpgp --cat > b
     netpgp: default key set to "C0596823"
     netpgp: default key set to "C0596823"
     pub 2048/RSA (Encrypt or Sign) 1b68dcfcc0596823 2004-01-12
     Key fingerprint: d415 9deb 336d e4cc cdfa 00cd 1b68 dcfc c059 6823
     uid              Alistair Crooks <agc@netbsd.org>
     uid              Alistair Crooks <agc@pkgsrc.org>
     uid              Alistair Crooks <agc@alistaircrooks.com>
     uid              Alistair Crooks <alistair@hockley-crooks.com>
     netpgp passphrase:
     Good signature for <stdin> made Mon Dec 21 18:25:02 2009
     using RSA (Encrypt or Sign) key 1b68dcfcc0596823
     pub 2048/RSA (Encrypt or Sign) 1b68dcfcc0596823 2004-01-12
     Key fingerprint: d415 9deb 336d e4cc cdfa 00cd 1b68 dcfc c059 6823
     uid              Alistair Crooks <alistair@hockley-crooks.com>
     uid              Alistair Crooks <agc@pkgsrc.org>
     uid              Alistair Crooks <agc@netbsd.org>
     uid              Alistair Crooks <agc@alistaircrooks.com>
     uid              Alistair Crooks (Yahoo!) <agcrooks@yahoo-inc.com>
     %

     For operations like signing and encrypting a file at the same time, the
     best way is to make use of pipelines:

     % netpgp --sign < example | netpgp --encrypt --userid=c0596823 > example.gpg
     netpgp: default key set to "C0596823"
     pub 2048/RSA (Encrypt or Sign) 1b68dcfcc0596823 2004-01-12
     Key fingerprint: d415 9deb 336d e4cc cdfa 00cd 1b68 dcfc c059 6823
     uid              Alistair Crooks <alistair@hockley-crooks.com>
     uid              Alistair Crooks <agc@pkgsrc.org>
     uid              Alistair Crooks <agc@netbsd.org>
     uid              Alistair Crooks <agc@alistaircrooks.com>
     uid              Alistair Crooks (Yahoo!) <agcrooks@yahoo-inc.com>
     netpgp passphrase:
     % netpgp --decrypt < example.gpg | netpgp --cat
     netpgp: default key set to "C0596823"
     netpgp: default key set to "C0596823"
     pub 2048/RSA (Encrypt or Sign) 1b68dcfcc0596823 2004-01-12
     Key fingerprint: d415 9deb 336d e4cc cdfa 00cd 1b68 dcfc c059 6823
     uid              Alistair Crooks <alistair@hockley-crooks.com>
     uid              Alistair Crooks <agc@pkgsrc.org>
     uid              Alistair Crooks <agc@netbsd.org>
     uid              Alistair Crooks <agc@alistaircrooks.com>
     uid              Alistair Crooks (Yahoo!) <agcrooks@yahoo-inc.com>
     netpgp passphrase:
     Good signature for <stdin> made Mon Feb 22 07:21:19 2010
     using RSA (Encrypt or Sign) key 1b68dcfcc0596823
     pub 2048/RSA (Encrypt or Sign) 1b68dcfcc0596823 2004-01-12
     Key fingerprint: d415 9deb 336d e4cc cdfa 00cd 1b68 dcfc c059 6823
     uid              Alistair Crooks <alistair@hockley-crooks.com>
     uid              Alistair Crooks <agc@pkgsrc.org>
     uid              Alistair Crooks <agc@netbsd.org>
     uid              Alistair Crooks <agc@alistaircrooks.com>
     uid              Alistair Crooks (Yahoo!) <agcrooks@yahoo-inc.com>
     ...contents of original file...
     %

EXIT STATUS
     The netpgp utility will return 0 for success, 1 if the file's signature
     does not match what was expected, or 2 if any other error occurs.

SEE ALSO
     netpgpkeys(1), ssh(1), getpass(3), libnetpgp(3), ssl(3), zlib(3)

STANDARDS
     J. Callas, L. Donnerhacke, H. Finney, D. Shaw, and R. Thayer, OpenPGP
     Message Format, RFC 4880, November 2007.

HISTORY
     The netpgp command first appeared in NetBSD 6.0.

AUTHORS
     Ben Laurie, Rachel Willmer, and overhauled and rewritten by Alistair
     Crooks <agc@NetBSD.org>.  This manual page was also written by Alistair
     Crooks.

NetBSD 6.0                     February 16, 2014                    NetBSD 6.0

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