[![status-badge](https://ci.codeberg.org/api/badges/15605/status.svg)](https://ci.codeberg.org/repos/15605)
[![License](https://img.shields.io/badge/license-GPL-blue.svg)](https://codeberg.org/scip/pcp/blob/master/LICENSE)

# Pretty Curved Privacy

Pretty Curved Privacy (pcp1) is a commandline utility which can be used
to encrypt files. pcp1 uses eliptc curve cryptography for encryption
(CURVE25519 by Dan J. Bernstein). While CURVE25519 is no 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 no accepted standard, pcp1 has to be
considered as 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 home.

# QUICKSTART

Lets say, Alicia and Bobby want to exchange encrypted messages. Here's
what the've got to do.

First, both have 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 to exchange the public key somehow (which is not my problem at
the moment, use ssh, encrypted mail, whatever). Once exchanged, they
have to import it:

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

They will see a response as this when 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

here 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 ..

If you want to have JSON support, you'll need to install the Jansson
library (optional):

    git clone git://github.com/akheron/jansson.git
    cd jansson
    autoreconf -i
    ./configure && make
    sudo make install
    cd ..

In order to use the python binding, you need to install the cffi python
package.

Next, build pcp:

    git clone git://codeberg.org/scip/pcp.git
    cd pcp
    meson setup build
    ninja -C build
    sudo ninja -C install

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>

## 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. 

Comitted by Alexander von Gernler in rev 1.7.


# AUTHORS

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

# LICENSE

Licensed under the GNU GENERAL PUBLIC LICENSE version 3.