is a

peer-to-peer Peer-to-peer (P2P) computing or networking is a distributed application architecture that partitions tasks or workloads between peers. Peers are equally privileged, equipotent participants in the network. They are said to form a peer-to-peer ...

file-sharing File sharing is the practice of distributing or providing access to digital media, such as computer programs, multimedia (audio, images and video), documents or electronic books. Common methods of storage, transmission and dispersion include ...

(P2P) application from Japan designed for use with Microsoft Windows. It was launched in 2006. Its

author An author is the writer of a book, article, play, mostly written work. A broader definition of the word "author" states: "''An author is "the person who originated or gave existence to anything" and whose authorship determines responsibility f ...

is known by the

pseudonym A pseudonym (; ) or alias () is a fictitious name that a person or group assumes for a particular purpose, which differs from their original or true name (orthonym). This also differs from a new name that entirely or legally replaces an individua ...

. Perfect Dark was developed with the intention for it to be the successor to both

Winny Winny (also known as WinNY) is a Japanese peer-to-peer (P2P) file-sharing program developed by Isamu Kaneko, a research assistant at the University of Tokyo in 2002. Like Freenet, a user must add an encrypted node list in order to connect to oth ...

and Share software. While Japan's Association for Copyright of Computer Software reported that in January 2014, the number of nodes connected on Perfect Dark () was less than on Share (), but more than on

(), Netagent in 2018 reported

being the largest with 50 000 nodes followed by Perfect Dark with 30 000 nodes followed by Share with 10 000. Netagent asserts that the number of nodes on Perfect Dark have fallen since 2015 while the numbers of

hold steady. Netagent reports that users of Perfect Dark are most likely to share books/manga. As of version 1.02 (2008), code-named "Stand Alone Complex", there is support for the program to run in English, an option that can be selected when the program is installed.

Overview

Perfect Dark is still being actively developed. The author does not ask that the program's users at this point become dedicated "users" of the software. Instead, the author asks them to participate in the test phase. Through this test phase, the author hopes for bug reports and discussion that will help shape Perfect Dark into a better program.

DKT+DHT+DU

The author implements an architecture called ''DKT+DHT+DU'' in the design of the network. These three parts compose the entire network. * "DKT" stands for Distributed Keyword Table. * "DHT" for

Distributed Hash Table A distributed hash table (DHT) is a distributed system that provides a lookup service similar to a hash table: key–value pairs are stored in a DHT, and any participating node can efficiently retrieve the value associated with a given key. The ...

. * "DU" for

distributed Distribution may refer to: Mathematics *Distribution (mathematics), generalized functions used to formulate solutions of partial differential equations *Probability distribution, the probability of a particular value or value range of a varia ...

Unity. "DKT" is mainly for providing effective file searching while "DHT" and "DU" is used for effective file sharing and enhancing anonymity.

Network bandwidth requirement

Perfect Dark has higher

bandwidth Bandwidth commonly refers to: * Bandwidth (signal processing) or ''analog bandwidth'', ''frequency bandwidth'', or ''radio bandwidth'', a measure of the width of a frequency range * Bandwidth (computing), the rate of data transfer, bit rate or thr ...

and

hard drive A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device that stores and retrieves digital data using magnetic storage with one or more rigid rapidly rotating platters coated with magne ...

space requirements than its predecessors

and Share. The minimum

upload Uploading refers to ''transmitting'' data from one computer system to another through means of a network. Common methods of uploading include: uploading via web browsers, FTP clients], and computer terminal, terminals ( SCP/ SFTP). Uploadin ...

speed is 100 kbit/s. Perfect Dark requires more network

and hard disk space than Winny or Share, forcing a fairer load on all users. If a user does not have Perfect Dark configured with the proper settings or if the user is unable to support the settings, download rates will be restricted and priority will be given to other users. This is intended to increase the retention rate of the Perfect Dark network.

Disk space requirement

It requires to share at minimum 40 GB of hard drive space, for its "Unity" folder (a huge

distributed hash table A distributed hash table (DHT) is a distributed system that provides a lookup service similar to a hash table: key–value pairs are stored in a DHT, and any participating node can efficiently retrieve the value associated with a given key. The ...

used as a

distributed data store A distributed data store is a computer network where information is stored on more than one node, often in a replicated fashion. It is usually specifically used to refer to either a distributed database where users store information on a ''numb ...

File system requirement

Perfect Dark requires

NTFS New Technology File System (NTFS) is a proprietary journaling file system developed by Microsoft. Starting with Windows NT 3.1, it is the default file system of the Windows NT family. It superseded File Allocation Table (FAT) as the preferred fil ...

file system instead of

FAT32 File Allocation Table (FAT) is a file system developed for personal computers. Originally developed in 1977 for use on floppy disks, it was adapted for use on hard disks and other devices. It is often supported for compatibility reasons by ...

, because FAT32 is limited to a file size of 4 GB, while Perfect Dark can download files up to the size of 32 GB.

Features

Distributed datastore

Like other Japanese sharing software, Perfect Dark has its own proprietary P2P network called "Unity". One of the biggest characteristics of Perfect Dark is its powerful search capability. By using

s, search performance is greatly improved compared to

or Share, making it unnecessary to rely on the construction of

node In general, a node is a localized swelling (a "knot") or a point of intersection (a vertex). Node may refer to: In mathematics * Vertex (graph theory), a vertex in a mathematical graph *Vertex (geometry), a point where two or more curves, lines ...

clusters. This frees users from inputting or switching cluster keywords and also enables users to search for files of different genres at the same time. This is in contrast to Winny and Share, where cluster keywords, such as "DVDISO" or "アニメ"/"anime" are used to specify what types of files the user is searching for. These keywords segregate the network and introduce delays when the user changes to them.

File search: tree search

The concept of " tree search" brings about strong search ability. In addition, the flexible use of AND, OR and NOT boolean operators helps filtering out undesirable results.

Text flow

Perfect Dark includes an original feature named "flow": a window where text lines written by users scroll vertically. Each user can write one little message (few lines and columns), and it will be displayed to the other peers using the flow feature.

Automated update

Since version 1.02 Perfect Dark has an option to automatically update itself through its own (Unity) network.

Messages boards

Perfect dark has a simple

message board An Internet forum, or message board, is an online discussion site where people can hold conversations in the form of posted messages. They differ from chat rooms in that messages are often longer than one line of text, and are at least temporar ...

feature. The boards are distributed into Unity network. The design is rudimentary. To get boards, these must be searched with the file search feature, with (for example) the Japanese keyword (board).

Security

The overall structure of the Perfect Dark network broadly resembles recent versions of

Freenet Freenet is a peer-to-peer platform for censorship-resistant, anonymous communication. It uses a decentralized distributed data store to keep and deliver information, and has a suite of free software for publishing and communicating on the Web ...

, only with a heavier use of distributed hash tables. The anonymity relies on a mixnet where traffic is forwarded according to certain probability, as well as the deniability of the

distributed data storage A distributed data store is a computer network where information is stored on more than one node, often in a replicated fashion. It is usually specifically used to refer to either a distributed database where users store information on a ''numb ...

("Unity") which is stored and transferred in encrypted blocks while the keys are distributed separately. Perfect Dark uses RSA (1024-bit) and AES (128-bit) to

encrypt In cryptography, encryption is the process of encoding information. This process converts the original representation of the information, known as plaintext, into an alternative form known as ciphertext. Ideally, only authorized parties can deci ...

data transmitted between peers. Exchanged keys are cached for efficiency. Published files and boards (including automatic updates from the author, where enabled) are usually signed with 160-bit

ECDSA In cryptography, the Elliptic Curve Digital Signature Algorithm (ECDSA) offers a variant of the Digital Signature Algorithm (DSA) which uses elliptic-curve cryptography. Key and signature-size As with elliptic-curve cryptography in general, the b ...

signatures. Automatic updates of the software are additionally protected with a 2048-bit RSA signature. The author believes that initially, a layer of obscurity due to the closed-source nature of the program will frustrate attempted attacks on its anonymity, as well as deter "free riders" and junk files degrading the network. However, the author has stated that it may become open-source in the future should an acceptable solution to these problems be found. The Japanese security firm NetAgent is claiming (2010) that they have created software capable of deciphering encrypted information such as the

IP address An Internet Protocol address (IP address) is a numerical label such as that is connected to a computer network that uses the Internet Protocol for communication.. Updated by . An IP address serves two main functions: network interface ident ...

of the original computer uploading a file as well as the file name and other details of Perfect Dark.

Legal issues

* A Perfect Dark user was arrested for the first time on 27 January 2010. The user had been uploading and sharing an episode of the Japanese animation TV series '' Fullmetal Alchemist: Brotherhood'' with Perfect Dark and was charged with breach of copyright law. * On 10 June 2010, a second user, a 43-year-old man, was arrested on the suspicion of uploading roughly one thousand

copyright A copyright is a type of intellectual property that gives its owner the exclusive right to copy, distribute, adapt, display, and perform a creative work, usually for a limited time. The creative work may be in a literary, artistic, educatio ...

ed files including the ''

Big Windup! , often shortened to just , is a Japanese baseball-themed manga series written and illustrated by Asa Higuchi. It has been serialized in Kodansha's ''seinen'' manga magazine '' Monthly Afternoon'' since September 2003, with its chapters colle ...

'' anime series. * On 8 October 2010, a 42-year-old woman was arrested for uploading the '' Mitsudomoe'' anime television series.

References

Anonymous file sharing networks File sharing networks Windows file sharing software Windows-only software Garlic routing