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.
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 firstname.lastname@example.org 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.
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 ..
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://github.com/tlinden/pcp.git cd pcp ./configure sudo make install cd ..
Optionally, you might run the unit tests:
To learn how to use pcp, read the manpage:
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