DESCRIPTION
    Pretty Curved Privacy (pcp1) is a commandline utility which can be used
    to encrypt files. pcp1 uses elliptic curve cryptography for encryption
    (CURVE25519 by Dan J. Bernstein). While CURVE25519 is not a worldwide
    accepted standard it hasn't been compromised by the NSA - which might be
    better, depending on your point of view.

    Caution: since CURVE25519 is not an accepted standard, pcp1 has to be
    considered experimental software. In fact, I wrote it just to learn
    about the curve and see how it works.

    Beside some differences it works like GNUPG. So, if you already know how
    to use gpg, you'll feel almost at home.

QUICKSTART
    Lets say, Alicia and Bobby want to exchange encrypted messages. Here's
    what they need to do.

    First, both have to create a secret key:

     Alicia                             Bobby
     pcp1 -k                            pcp1 -k

    After entering their name, email address, and a passphrase to protect the
    key, it will be stored in their vault file (by default ~/.pcpvault).

    Now, both of them have to export the public key, which has to be
    imported by the other one. With pcp you can export the public part of
    your primary key, but the better solution is to export a derived public
    key especially for the recipient:

     Alicia                             Bobby
     pcp1 -p -r Bobby -O alicia.pub     pcp1 -p -r Alicia -O bobby.pub

    They've got to exchange the public key somehow (which is not my problem at
    the moment, use ssh, encrypted mail, etc). Once exchanged, they
    have to import it:

     Alicia                             Bobby
     pcp1 -K -I bobby.pub               pcp1 -K -I alicia.pub

    They will see a response when this is done:

     key 0x29A323A2C295D391 added to .pcpvault.

    Now, Alicia finally writes the secret message, encrypts it, and sends it
    to Bobby, who in turn decrypts it:

     Alicia                             Bobby
     echo "Love you, honey" > letter
     pcp1 -e -r Bobby -I letter -O letter.asc
     cat letter.asc | mail bobby@foo.bar

                                        pcp1 -d -I letter.asc | less

    And that's it.

    Please note the big difference to GPG though: both Alicia AND Bobby have
    to enter the passphrase for their secret key! That's the way CURVE25519
    works: you encrypt a message using your secret key and the recipients
    public key and the recipient does the opposite, he uses his secret key
    and your public key to actually decrypt the message.

    Oh - and if you're wondering why I named them Alicia and Bobby: I was
    just sick of Alice and Bob. We're running NSA-free, so we're using other
    sample names as well.

FILES AND PIPES
    Pcp behaves like any other unix tool. If not otherwise specified it will
    read input from standard input (STDIN) and print output to standard
    output (STDOUT). For instance:

     pcp1 -e -O output

    will read the text to be encrypted from standard input, because -I has
    not been specified. It works the same with -O:

     pcp1 -e -I myfile

    In this case the encrypted result will be written to standard output.

    Therefore it is possible to use pcp within pipes. Another more realistic
    example:

     ssh remote cat file | pcp1 -ez | mailx -s 'as requested' bob@somewhere

    Here we encrypt a file symmetrically without downloading it from a
    remote ssh server and sending the encrypted result via email to someone.

    The behavior is the same with any other functionality where files are
    involved like importing or exporting keys. However, there's one
    exception: If the option -X (--password-file) has been used and is set
    to -, then this will take precedence over any other possible use of
    standard input. So if you want to encrypt something and don't specify an
    input file you cannot use -X -, and vice versa. IF you use -X - the
    passphrase will be read from standard input, which then can't be used
    further for input files elsewhere. Pcp will exit with an error in such a
    case.

INSTALLATION
    There are currently no packages available, so pcp has to be compiled
    from source. Follow these steps:

    First, you will need libsodium:

     git clone git://github.com/jedisct1/libsodium.git
     cd libsodium
     ./autogen.sh
     ./configure && make check
     sudo make install
     sudo ldconfig
     cd ..

    Next, pcp:

     git clone git://github.com/tlinden/pcp.git
     cd pcp
     ./configure
     sudo make install
     cd ..

    Optionally, you might run the unit tests:

     make test

DOCUMENTATION
    To learn how to use pcp, read the manpage:

     man pcp1

COPYRIGHT
    Copyright (c) 2013-2015 by T.v.Dein <tom AT vondein DOT org>

ADDITIONAL COPYRIGHTS
    ZeroMQ Z85 encoding routine
         Copyright (c) 2007-2013 iMatix Corporation
         Copyright (c) 2009-2011 250bpm s.r.o.
         Copyright (c) 2010-2011 Miru Limited
         Copyright (c) 2011 VMware, Inc.
         Copyright (c) 2012 Spotify AB

    Tarsnap readpass helpers
         Copyright 2009 Colin Percival

    jen_hash() hash algorithm
         Bob Jenkins, Public Domain.

    UTHASH hashing macros
         Copyright (c) 2003-2013, Troy D. Hanson

    Random art image from OpenSSH keygen
         Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.

         Committed by Alexander von Gernler in rev 1.7.

    Every incorporated source code is opensource and licensed under the GPL
    as well.

AUTHORS
    *T.v.Dein <tom AT vondein DOT org*>

LICENSE
    Licensed under the GNU GENERAL PUBLIC LICENSE version 3.

HOME
    The homepage of Pretty Curved Privacy can be found on
    http://www.daemon.de/PrettyCurvedPrivacy. The source is on Github:
    https://github.com/TLINDEN/pcp