### para_write ###
A modular audio stream writer. It supports a simple file writer
-output plug-in and optional WAV/raw players for ALSA (Linux) and for
-coreaudio (Mac OS). para_write can also be used as a stand-alone WAV
-or raw audio player.
+output plug-in and optional WAV/raw players for ALSA (Linux) and OSS.
+para_write can also be used as a stand-alone WAV or raw audio player.
### para_play ###
git clone git://git.tuebingen.mpg.de/osl
cd osl && make && sudo make install && sudo ldconfig
- sudo apt-get install autoconf libssl-dev help2man gengetopt \
+ sudo apt-get install autoconf libssl-dev help2man gengetopt m4 \
libmad0-dev libid3tag0-dev libasound2-dev libvorbis-dev \
libfaad-dev libspeex-dev libFLAC-dev libsamplerate-dev realpath \
libasound2-dev libao-dev libreadline-dev libncurses-dev \
- [help2man](ftp://ftp.gnu.org/pub/gnu/help2man) is used to create
the man pages.
+- [m4](ftp://ftp.gnu.org/pub/gnu/m4/). Some source files are generated
+from templates by the m4 macro processor.
+
Optional:
- [openssl](http://www.openssl.org/) or
para_server uses a challenge-response mechanism to authenticate
requests from incoming connections, similar to ssh's public key
authentication method. Authenticated connections are encrypted using
-a stream cipher, either RC4 or AES in integer counter mode.
+the AES stream cipher in integer counter mode.
-In this chapter we briefly describe RSA, RC4 and AES, and sketch the
+In this chapter we briefly describe RSA and AES, and sketch the
[authentication handshake](#Client-server.authentication)
between para_client and para_server. User management is discussed
in the section on [the user_list file](#The.user_list.file).
server. Connecting para_audiod is a different matter and is described
in a [separate section](#Connecting.para_audiod).
-RSA, RC4, AES
--------------
+RSA and AES
+-----------
-RSA is an asymmetric block cipher which is used in many applications,
-including ssh and gpg. An RSA key consists in fact of two keys,
+A block cipher is a transformation which operates on fixed-length
+blocks. For symmetric block ciphers the transformation is determined
+by a single key for both encryption and decryption. For asymmetric
+block ciphers, on the other hand, the key consists of two parts,
called the public key and the private key. A message can be encrypted
-with either key and only the counterpart of that key can decrypt
-the message. While RSA can be used for both signing and encrypting
-a message, paraslash uses RSA only for the latter purpose. The
-RSA public key encryption and signatures algorithms are defined in
-detail in RFC 2437.
-
-RC4 is a stream cipher, i.e. the input is XORed with a pseudo-random
-key stream to produce the output. Decryption uses the same function
-calls as encryption. While RC4 supports variable key lengths,
-paraslash uses a fixed length of 256 bits, which is considered a
-strong encryption by today's standards. Since the same key must never
-be used twice, a different, randomly-generated key is used for every
-new connection.
+with either key and only the counterpart of that key can decrypt the
+message. Asymmetric block ciphers can be used for both signing and
+encrypting a message.
+
+RSA is an asymmetric block cipher which is used in many applications,
+including ssh and gpg. The RSA public key encryption and signatures
+algorithms are defined in detail in RFC 2437. Paraslash relies on
+RSA for authentication.
+
+Stream ciphers XOR the input with a pseudo-random key stream to produce
+the output. Decryption uses the same function calls as encryption.
+Any block cipher can be turned into a stream cipher by generating the
+pseudo-random key stream by encrypting successive values of a counter
+(counter mode).
AES, the advanced encryption standard, is a well-known symmetric block
-cipher, i.e. a transformation operating on fixed-length blocks which
-is determined by a single key for both encryption and decryption. Any
-block cipher can be turned into a stream cipher by generating
-a pseudo-random key stream by encrypting successive values of a
-counter. The AES_CTR128 stream cipher used in paraslash is obtained
-in this way from the AES block cipher with a 128 bit block size.
+cipher. Paraslash employs AES in counter mode as described above to
+encrypt communications. Since a stream cipher key must not be used
+twice, a random key is generated for every new connection.
Client-server authentication
----------------------------
the session key known to both peers.
paraslash relies on the quality of the pseudo-random bytes provided
-by the crypto library (openssl or libgcrypt), on the security of the
-implementation of the RSA, RC4 and AES crypto routines and on the
+by the crypto library (openssl or libgcrypt), on the security of
+the implementation of the RSA and AES crypto routines and on the
infeasibility to invert the SHA1 function.
Neither para_server or para_client create RSA keys on their
The image, lyrics, moods and playlists tables are all blob tables.
Blob tables consist of three columns each: The identifier which is
-a positive non-negative number that is auto-incremented, the name
-(an arbitrary string) and the content (the blob).
+a positive number that is auto-incremented, the name (an arbitrary
+string) and the content (the blob).
All blob tables support the same set of actions: cat, ls, mv, rm
and add. Of course, _add_ is used for adding new blobs to the table
### The score table ###
-Unlike all other tables the contents of the score table remain in
-memory and are never stored on disk. The score table contains two
-columns: The SHA1 hash value (of an audio file) and its current
-score.
+The score table describes those audio files which are admissible for
+the current mood or playlist (see below). The table has two columns:
+a pointer to a row of the audio file table and a score value.
-However, only those files which are admissible for the current mood
-or playlist are contained in the score table. The audio file selector
-always chooses the row with the highest score as the file to stream
-next. While doing so, it computes the new score and updates the
-last_played and the num_played fields in the audio file table.
-
-The score table is recomputed by the select command which loads a
-mood or playlist. Audio files are chosen for streaming from the rows
-of the score table on a highest-score-first basis.
+Unlike all other tables of the database, the score table remains in
+memory and is never stored on disk. It is initialized at startup and
+recomputed when the select command loads a new mood or playlist.
+When the audio file selector is asked to open the next audio file,
+it picks the row with the highest score, opens the corresponding
+file and passes the file descriptor to the virtual streaming system.
+At this point the last_played and the num_played fields of the selected
+file are updated and the score is recomputed.
Playlists and moods
-------------------
also limited. For example only one application can open the device
at any time. The OSS writer is activated by default on BSD Systems.
-- *OSX*. Mac OS X has yet another API called CoreAudio. The OSX writer
-for this API is only compiled in on such systems and is of course
-the default there.
-
- *FILE*. The file writer allows to capture the audio stream and
write the PCM data to a file on the file system rather than playing
it through a sound device. It is supported on all platforms and is
Development
===========
+Contributing
+------------
+
+Paraslash is an open source project and contributions are
+welcome. Here's a list of things you can do to help the project:
+
+- Report problems with building, installing or running the software.
+ In particular, test the experimental git branches ("next" and "pu").
+ This helps to identify and fix problems before the code gets merged
+ and thus keeps the master branch as stable as possible.
+- Proofread the documentation (manual, web pages, man pages, source
+ code documentation) and point out unclear or poorly written parts. If
+ you are a native English speaker you will easily find a lot of text
+ that could be improved.
+- Run analysis tools (coverity, afl, sparse, etc.) and report issues
+ found by those tools.
+- Suggest new features you would like to see implemented.
+- Compile and test on your favorite architecture or operating
+ system. The code is tested only on a limited set of systems, so you
+ will probably encounter problems when building on different systems.
+- Post about about paraslash on your blog or on social networks.
+- Build and maintain Debian/RPM packages for your favorite distribution.
+
+Note that there is no mailing list, no bug tracker and no discussion
+forum for paraslash. If you'd like to contribute, or have questions
+about contributing, send email to Andre Noll <maan@tuebingen.mpg.de>.
+
Tools
-----
paraslash development. It is necessary for cloning the git repository
and for getting updates.
-- [m4](ftp://ftp.gnu.org/pub/gnu/m4/). Some input files for gengetopt
-are generated from templates by the m4 macro processor.
-
- [autoconf](ftp://ftp.gnu.org/pub/gnu/autoconf/) GNU autoconf creates
the configure file which is shipped in the tarballs but has to be
generated when compiling from git.
The preferred coding style for paraslash coincides more or less
with the style of the Linux kernel. So rather than repeating what is
-written [there](http://www.kernel.org/doc/Documentation/CodingStyle),
+written [there](http://www.kernel.org/doc/Documentation/process/coding-style.rst),
here are the most important points.
- Burn the GNU coding standards.
projects / paraslash.git / blobdiff