tahoe-lafs/relnotes.txt

NEW VERSION RELEASED

We are pleased to announce the release of version 0.4 of
Allmydata-Tahoe, a secure, decentralized storage grid under a
free-software licence.  This is the follow-up to v0.3 which was
released June 6, 2007 (see [1]).

Since then we've made several improvements, including:

 * Add encrypted, mutable directories, so that you can organize your
   files into directories, change the contents of directories, and
   share your directories with your friends, without thereby sharing
   your directories with anyone else -- not even with the owners of
   the servers that host your directories.

 * make it so that web browsers can connect to the Tahoe node securely
   with https (ticket #55)


For complete details, see this web page which shows all ticket
changes, repository checkins, and wiki changes from June 11 to today,
June 29: [2].

Allmydata-Tahoe v0.4 is incompatible with v0.3 due to the new
encrypted directory structure, among other things.  (Note that this
applies only to directories -- individual files uploaded with v0.3 are
probably downloadable with v0.4.)


WHAT IS IT GOOD FOR?

With Tahoe, you can back up your files in a distributed way onto a set
of computers, such that if some of the computers fail or become
unavailable, you can still retrieve your data from the remainder.  You
can also securely share your files with other users.

This release is targeted at hackers and users who are willing to use a
text-oriented web user interface, or a command-line user interface.
(Or a RESTful API.  Just telnet to localhost and type HTTP requests to
get started...)

Because this software is new and little tested, it is not yet
recommended for storage of highly confidential data nor for important
data which is not otherwise backed up, but it is useful for
experimentation, prototyping, and extension.

This release of Allmydata-Tahoe is suitable for Use Case #2: "groups
of friends who want to share backup and file-sharing" (see the wiki
page "UseCases": [3]).  It is easy to set up a private grid which is
securely shared among a specific, limited set of friends.  Files
uploaded to this shared grid will be available to all friends, even
when some of the computers are unavailable.  It is also easy to use a
public grid, but to encrypt individual files and directories so that
only intended recipients can read them.


LICENCE

Tahoe is offered under the GNU General Public License (v2 or later),
with the added permission that, if you become obligated to release a
derived work under this licence (as per section 2.b), you may delay
the fulfillment of this obligation for up to 12 months.


INSTALLATION

This release of Tahoe works on Linux/x86, Linux/amd64, Mac/Intel,
Mac/PPC, Windows-native, and Cygwin.

To install, download the tarball [4], untar it, go into the resulting
directory, and follow the directions in the README [5].


USAGE

Once installed, create a "client node".  Instruct this client node to
connect to a specific "introducer node" by means of config files in
the client node's working directory.  To join a public grid, copy in
the .furl files for that grid.  To create a private grid, run your own
introducer, and copy its .furl files.  See the README for step-by-step
instructions.

Each client node runs a local webserver (enabled by writing the
desired port number into a file called 'webport').  The front page of
this webserver shows the node's status, including which introducer is
being used and which other nodes are connected.  Links from the status
page lead to others that give access to a shared virtual filesystem,
in which each directory is represented by a separate page.  Each
client node also has a separate (non-shared) virtual filesystem.  Each
directory page shows a list of the files available there, with
download links, and forms to upload new files.

Other ways to access the filesystem are planned: please see the
roadmap.txt [6] for some rough details.


HACKING AND COMMUNITY

Please join the mailing list [7] to discuss the ideas behind Tahoe and
extensions of and uses of Tahoe.  Patches that extend and improve
Tahoe are gratefully accepted -- roadmap.txt shows the next
improvements that we plan to make and CREDITS lists the names of
people who've contributed to the project.  You can browse the revision
control history, source code, and issue tracking at the Trac instance
[8].  Please see the buildbot [9], which shows how Tahoe builds and
passes unit tests on each checkin, and the code coverage results [10]
and percentage-covered graph [11], which show how much of the Tahoe
source code is currently exercised by the test suite.


NETWORK ARCHITECTURE

Each peer maintains a connection to each other peer.  A single
distinct server called an "introducer" is used to discover other peers
with which to connect.

To store a file, the file is encrypted and erasure coded, and each
resulting share is uploaded to a different peer.  The secure hash of
the encrypted file and the encryption key are packed into a URI,
knowledge of which is necessary and sufficient to recover the file.

To fetch a file, starting with the URI, a subset of shares is
downloaded from peers, the file is reconstructed from the shares, and
then decrypted.

A single distinct server called a "vdrive server" maintains a global
mapping from pathnames/filenames to URIs.

We are acutely aware of the limitations of decentralization and
scalability inherent in this version.  In particular, the
completely-connected property of the grid and the requirement of a
single distinct introducer and vdrive server limits the possible size
of the grid.  We have plans to loosen these limitations (see
roadmap.txt).  Currently it should be noted that the grid already
depends as little as possible on the accessibility and correctness of
the introduction server and the vdrive server.  Also note that the
choice of which servers to use is easily configured -- you should be
able to set up a private grid for you and your friends almost as
easily as to connect to our public test grid.


SOFTWARE ARCHITECTURE

Tahoe is a "from the ground-up" rewrite, inspired by Allmydata's
existing consumer backup service.  It is primarily written in the
Python programming language.

Tahoe is based on the Foolscap library [12] which provides a remote
object protocol inspired by the capability-secure "E" programming
language [13].  Foolscap allows us to express the intended behavior of
the distributed grid directly in object-oriented terms while relying
on a well-engineered, secure transport layer.

The network layer is provided by the Twisted library [14].
Computationally intensive operations are performed in native compiled
code, such as the "zfec" library for fast erasure coding (also
available separately: [15]).

Tahoe is sponsored by Allmydata, Inc. [16], a provider of consumer
backup services.  Allmydata, Inc. contributes hardware, software,
ideas, bug reports, suggestions, demands, and money (employing several
Allmydata-Tahoe hackers and allowing them to spend part of their work
time on the next-generation, free-software project).  We are eternally
grateful!


Zooko O'Whielacronx and Brian Warner
on behalf of the Allmydata-Tahoe team
June 29, 2007
Boulder, Colorado and San Francisco, California


[1]  http://allmydata.org/trac/tahoe/browser/relnotes.txt?rev=790
[2]  http://allmydata.org/trac/tahoe/timeline?from=2007-06-29&daysback=17&changeset=on&ticket=on&wiki=on&update=Update
[3]  http://allmydata.org/trac/tahoe/wiki/UseCases
[4]  http://allmydata.org/source/tahoe/tahoe-0.4.tar.gz
[5]  http://allmydata.org/trac/tahoe/browser/README?rev=844
[6]  http://allmydata.org/trac/tahoe/browser/roadmap.txt
[7]  http://allmydata.org/cgi-bin/mailman/listinfo/tahoe-dev
[8]  http://allmydata.org/trac/tahoe
[9]  http://allmydata.org/buildbot
[10] http://allmydata.org/tahoe-figleaf/figleaf/
[11] http://allmydata.org/tahoe-figleaf-graph/hanford.allmydata.com-tahoe_figleaf.html
[12] http://twistedmatrix.com/trac/wiki/FoolsCap
[13] http://erights.org/
[14] http://twistedmatrix.com/
[15] http://allmydata.org/trac/tahoe/browser/src/zfec
[16] http://allmydata.com