BackupHDDVD

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BackupHDDVDはコマンドラインおよびグラフィカルユーザインターフェースの双方で利用可能な、AACSによるコピーガードが搭載されている商業HD DVDディスクの正当な解析と、バックアップのための無償のオープンソースユーティリティです。

このソフトウェアはMuslix64というハンドルネームの人物が著作権を所有しています。

By itself the program, which consists largely of an implementation of Java-based sample code made freely available by the entity which oversees AACS licensing,^[1] cannot be used to successfully decrypt a disk's contents.^[2] A user wanting to use the software to extract an unencrypted copy of a disk's contents would need to have obtained either a disk's volume or title key separately, a complex task with which neither BackupHDDVD nor its author provide any assistance.^[3]^[4]

For several weeks after the utility's release no claims of having been able to successfully use the author's key extraction technique were made.^[5]^[6] However, in mid-January, a key was published and several others quickly discovered a method which could be used to extract further keys.^[7]

[編集] 経歴

On December 18 2006 a video which claims to show BackupHDDVD being used to decrypt and copy the film Full Metal Jacket to a hard drive was uploaded^[8] to YouTube. This video has since been removed at the request of Warner Brothers Entertainment, citing copyrighted material being used without permission.^[9] Two days after the video was uploaded, the utility, along with its source code and documentation, was uploaded to a file hosting service. A link to the download was then posted^[10] in a thread started by the utility's creator on the forums of Doom9, a website devoted to DVD backup.^[11]

The utility's documentation, along with the forum post, contained vague hints as to how keys necessary for a successful decryption could be extracted. The author elaborated in another post, claiming that keys could be obtained by exploiting the necessity for them to be held in memory in order to facilitate playback in the PowerDVD software.^[12] Cyberlink, the company which sells PowerDVD, has since denied claims that their software could be used to obtain title keys.^[13]^[14]

On January 2 2007 the author posted an updated version of the BackupHDDVD utility, version 1.0, which included support for the decoding of disks using volume keys, among several other new features.^[15]^[16] Subsequent versions which were released by others included a basic GUI and support for automatically obtaining volume keys from the internet.

muslix64 made a pm interview with slyck.com on January 24, explaining how and why he created BackupHDDVD and discussing the future of digital restriction systems.^[17]

[編集] 制限事項

Currently, BackupHDDVD does not properly decrypt titles which use the in-movie experience technology. 今の所、BackupHDDVDは、Interactive content技術を含むタイトルを適切に解読できません。 The utility also cannot reproduce the navigation functions of HD-DVD EVOBs. また、HD-DVDの案内機能を複製することもできません。 Arguably a limitation, users must have either obtained appropriate keys themselves, or found them elsewhere, in order for BackupHDDVD to work. ほぼ間違いなく、制限として、使用者は暗号鍵を自分自身で見つけるか、あるいはどこかで探さなければなりません。

[編集] 反響

Reaction to the utility by Doom9 forum members, bloggers, and mainstream media has been mixed. Doom9 forum のmember達や,bloggerたち、そしてマスメディアの反応は混ざったものだ。 Some hail it as a victory for consumers' fair use rights, while others are expressing concerns that it will be used for piracy. ある人々はそれ（このソフトのこと）を消費者の権利の勝利として歓迎し、だが、他の人々は海賊行為として心配することを表現している。 Others fear that the compromise of HD DVD's security will entice some studios into adopting the competing Blu-Ray format instead.^[18] The consortium behind the HD DVD format and the studios delivering films on the format have released no official statement beyond that they are investigating the utility's claims.^[19]

Initially, there was speculation that the device key belonging to the version of PowerDVD allegedly used by the utility's author to extract keys for use in BackupHDDVD would be added to revocation lists in future HD DVD titles, preventing playback of any disks not already released.^[20] Cyberlink has since claimed that PowerDVD could not be used to obtain any of the needed keys.^[21] In the case of player revocation, a user wanting to view a new film would be forced to upgrade their HD-DVD player software to a version in which the exploit is not possible, thereby theoretically limiting the exploit's damage to disks released before the flaw was found in the player software.^[22]^[23]

After several weeks of collaboration, users of the Doom9 forum were able to extract the needed keys from InterVideo WinDVD 8.^[24] Questions still remain as to whether CyberLink's claim that PowerDVD could not be used to obtain keys is valid.

[編集] AACSのクラックに関する報道について

'BackupHDDVD'が公開リリースされた際、いくつかの記事によってAACSが「破られた」と報じられましたが、AESやAACSの基礎技術に脆弱性は見つかっておらず、また実際のところ作者が復号を行った際に使われた暗号鍵はメディアプレイヤーへのサイドチャネル攻撃によって取得されたものであるため、このソフトウェア単体で復号を行うことは不可能です。