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This is a brief overview of the changes between the GnuPG 1.2 series
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and the new GnuPG 1.4 series. To read the full list of highlights for
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each revision that led up to 1.4, see the NEWS file in the GnuPG
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distribution. This document is based on the NEWS file, and is thus
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the highlights of the highlights.
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When upgrading, note that RFC-2440, the OpenPGP standard, is currently
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being revised. Most of the revisions in the latest draft (2440bis-12)
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have already been incorporated into GnuPG 1.4.
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OpenPGP supports many different algorithms for encryption, hashing,
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and compression, and taking into account the OpenPGP revisions, GnuPG
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1.4 supports a slightly different algorithm set than 1.2 did.
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The SHA256, SHA384, and SHA512 hashes are now supported for read and
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The BZIP2 compression algorithm is now supported for read and write.
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Due to the recent successful attack on the MD5 hash algorithm
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(discussed in <http://www.rsasecurity.com/rsalabs/node.asp?id=2738>,
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among other places), MD5 is deprecated for OpenPGP use. It is still
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allowed in GnuPG 1.4 for backwards compatibility, but a warning is
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given when it is used.
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The TIGER/192 hash is no longer available. This should not be
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interpreted as a statement as to the quality of TIGER/192 - rather,
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the revised OpenPGP standard removes support for several unused or
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mostly unused hashes, and TIGER/192 was one of them.
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Similarly, Elgamal signatures and the Elgamal signing key type have
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been removed from the OpenPGP standard, and thus from GnuPG. Please
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do not confuse Elgamal signatures with DSA or DSS signatures or with
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Elgamal encryption. Elgamal signatures were very rarely used and were
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not supported in any product other than GnuPG. Elgamal encryption was
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and still is part of OpenPGP and GnuPG.
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Very old (pre-1.0) versions of GnuPG supported a nonstandard (contrary
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to OpenPGP) Elgamal key type. While no recent version of GnuPG
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permitted the generation of such keys, GnuPG 1.2 could still use them.
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GnuPG 1.4 no longer allows the use of these keys or the (also
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nonstandard) messages generated using them.
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At build time, it is possible to select which algorithms will be built
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into GnuPG. This can be used to build a smaller program binary for
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embedded uses where space is tight.
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GnuPG 1.4 does all keyserver operations via plugin or helper
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applications. This allows the main GnuPG program to be smaller and
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simpler. People who package GnuPG for various reasons have the
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flexibility to include or leave out support for any keyserver type as
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Support for fetching keys via HTTP and finger has been added. This is
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mainly useful for setting a preferred keyserver URL like
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"http://www.jabberwocky.com/key.asc". or "finger:wk@g10code.com".
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The LDAP keyserver helper now supports storing, retrieving, and
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searching for keys in both the old NAI "LDAP keyserver" as well as the
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more recent method to store OpenPGP keys in standard LDAP servers.
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This is compatible with the storage schema that PGP uses, so both
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products can interoperate with the same LDAP server.
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The LDAP keyserver helper is compatible with the PGP company's new
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"Global Directory" service.
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If the LDAP library you use supports LDAP-over-TLS and LDAPS, then
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GnuPG detects this and supports them as well. Note that using TLS or
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LDAPS does not improve the security of GnuPG itself, but may be useful
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in certain key distribution scenarios.
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HTTP Basic authentication is now supported for all HKP and HTTP
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keyserver functions, either through a proxy or via direct access.
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The HKP keyserver plugin supports the new machine-readable key
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listing format for those keyservers that provide it.
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IPv6 is supported for HKP and HTTP keyserver access.
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When using a HKP keyserver with multiple DNS records (such as
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subkeys.pgp.net which has the addresses of multiple servers around the
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world), all DNS address records are tried until one succeeds. This
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prevents a single down server in the rotation from stopping access.
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DNS SRV records are used in HKP keyserver lookups to allow
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administrators to load balance and select keyserver ports
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Timeout support has been added to the keyserver plugins. This allows
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users to set an upper limit on how long to wait for the keyserver
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Preferred Keyserver URL
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-----------------------
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Preferred keyserver support has been added. Users may set a preferred
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keyserver via the --edit-key command "keyserver". If the
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--keyserver-option honor-keyserver-url is set (and it is by default),
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then the preferred keyserver is used when refreshing that key with
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The --sig-keyserver-url option can be used to inform signature
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recipients where the signing key can be downloaded. When verifying
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the signature, if the signing key is not present, and the keyserver
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options honor-keyserver-url and auto-key-retrieve are set, this URL
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will be used to retrieve the key.
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GnuPG 1.4 supports OpenPGP trust signatures, which allow a user to
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specify the trust level and distance from the user along with the
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signature so users can delegate different levels of certification
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ability to other users, possibly restricted by a regular expression on
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GnuPG 1.4 supports several ways of looking at trust:
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Classic - The classic PGP trust model, where people sign each others
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keys and thus build up an assurance (called "validity") that
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the key belongs to the right person. This was the default
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trust model in GnuPG 1.2.
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Always - Bypass all trust checks, and make all keys fully valid.
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Direct - Users may set key validity directly.
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PGP - The PGP 7 and 8 behavior which combines Classic trust with trust
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signatures overlaid on top. This is the default trust model in
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The OpenPGP Smartcard
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---------------------
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GnuPG 1.4 supports the OpenPGP smartcard
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(<http://www.g10code.de/p-card.html>)
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Secret keys may be kept fully or partially on the smartcard. The
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smartcard may be used for primary keys or subkeys.
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Other Interesting New Features
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------------------------------
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For those using Security-Enhanced Linux <http://www.nsa.gov/selinux/>,
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the configure option --enable-selinux-support prevents GnuPG from
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processing its own files (i.e. reading the secret keyring for
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something other than getting a secret key from it). This simplifies
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writing ACLs for the SELinux kernel.
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Readline support is now available at all prompts if the system
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provides a readline library.
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GnuPG can now create messages that can be decrypted with either a
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passphrase or a secret key. These messages may be generated with
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--symmetric --encrypt or --symmetric --sign --encrypt.
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--list-options and --verify-options allow the user to customize
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exactly what key listings or signature verifications look like,
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enabling or disabling things such as photo display, preferred
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keyserver URL, calculated validity for each user ID, etc.
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The --primary-keyring option designates the keyring that the user
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wants new keys imported into.
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The --hidden-recipient (or -R) command encrypts to a user, but hides
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the identity of that user. This is the same functionality as
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--throw-keyid, but can be used on a per-user basis.
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Full algorithm names (e.g. "3DES", "SHA1", "ZIP") can now be used
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interchangeably with the short algorithm names (e.g. "S2", "H2", "Z1")
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anywhere algorithm names are used in GnuPG.
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The --keyid-format option selects short (99242560), long
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(DB698D7199242560), 0xshort (0x99242560), or 0xlong
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(0xDB698D7199242560) key ID displays. This lets users tune the
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display to what they prefer.
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While it is not recommended for extended periods, it is possible to
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run both GnuPG 1.2.x and GnuPG 1.4 during the transition. To aid in
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this, GnuPG 1.4 tries to load a config file suffixed with its version
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before it loads the default config file. For example, 1.4 will try
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for gpg.conf-1.4 and gpg.conf-1 before falling back to the regular