* What's this? EasyPG is an all-in-one GnuPG interface for Emacs. It has two aspects: convenient tools which allow to use GnuPG from Emacs (EasyPG Assistant), and a fully functional interface library to GnuPG (EasyPG Library). * Features The EasyPG Assistant provides the following features: - Keyring browser. - Cryptographic operations on regions. - Cryptographic operations on files. - Dired integration. - Encryption/decryption of *.gpg files. The EasyPG Library provides the following features: - The API covers most functions of GnuPG like GPGME. - S/MIME support using gpgsm. - Designed to avoid potential security pitfalls around Emacs * Requirements ** GNU Emacs 21.4, XEmacs 21.4, or later ** GnuPG 1.4.3 or later Earlier versions are supported but not recommended. * Quick start ** Installation $ ./configure $ sudo make install Add the following line to your ~/.emacs (require 'epa-setup) Restart emacs and type `M-x epa- TAB', and you will see a lot of commands available. For example, - To browse your keyring, type `M-x epa-list-keys' - To create a cleartext signature of the region, type `M-x epa-sign-region' You can also do some cryptographic operations from dired. M-x dired (mark some files) : e (or M-x epa-dired-do-encrypt) (select recipients by 'm' and click [OK]) * MUA Integration The EasyPG Library can be used in combination with various MUA (Mail User Agents). ** CVS version of Gnus CVS version of Gnus uses EasyPG by default. To make sure of that, check mml2015-use set to 'epg. Other options which affect on the EasyPG are mml2015-signers mml2015-encrypt-to-self mml2015-cache-passphrase mml2015-passphrase-cache-expiry mml2015-verbose NOTE: You don't need pgg-epg.el in this case. ** PGG based MUA PGG is outdated PGP library used by old Gnus (<= v5.11), MH-E, etc. There is a PGG backend written using EasyPG called pgg-epg.el. However, EasyPG API is a superset of PGG and pgg-epg.el provides nothing but compatibility with PGG. *** Limitations of PGG As I noted "PGG is outdated PGP library" above, PGG has several limitations. For example - PGG can't handle a message signed with multiple keys. - PGG can't prompt a user which key is being used. - PGG can't create a binary PGP messages. - PGG doesn't provide a way to select keys per cryptographic operation. - PGG ignores GnuPG's trust metrics. ** SEMI based MUA SEMI is the MIME library used by Wanderlust, cmail, T-gnus, etc. There is an EasyPG capable SEMI library called EMIKO-EasyPG. It can be downloaded from the same site of the EasyPG distribution point. * Security There are security pitfalls around Emacs. EasyPG is written with avoiding them. ** Passphrase may leak to a temporary file. The function call-process-region writes data in region to a temporary file. If your PGP library used this function, your passphrases would leak to the filesystem. The EasyPG Library does not use call-process-region to communicate with a gpg subprocess. ** Passphrase may be stolen from a core file. If Emacs crashes and dumps core, Lisp strings in memory are also dumped within the core file. read-passwd function clears passphrase strings by (fillarray string 0) to avoid this risk. However, Emacs performs compaction in gc_sweep phase. If GC happens before fillarray, passphrase strings may be moved elsewhere in memory. Therefore, passphrase caching in elisp is generally a bad idea. The EasyPG Library dares to disable passphrase caching. Fortunately, there is more secure way to cache passphrases - use gpg-agent.