Ed2k URI scheme: Difference between revisions

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Like other URI protocols, web browsers can be configured to automatically handle ed2k URIs. After installing an [[Comparison of eDonkey software|eD2k client]], the eD2k protocol is optionally registered so that clicking on it in the browser automatically starts the download or asks whether the user wants to start downloading.

== File link format ==ccccccc

File links are preceded with the "file" token, which indicates that this is a file link, as opposed to a <code>server</code>, <code>serverlist</code>, <code>nodelist</code> or <code>friend</code> link. The typical eD2k file link also includes the [[filename]] and the file size. An example (a link to the 15&nbsp;MB Purist Edit trailer) is provided below:

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The eD2k hash function is a [[hash list|root hash]] of a list of [[MD4]] [[hash function|hashes]]. It gives a different result than a simple usage of the MD4 algorithm.

The file data is divided into full ''chunks'' of 9500 KiB (9728000 bytes) plus a remainder chunk, and a separate 128-bit MD4 checksum is computed for each. If the file is greater thanccthan 9500 KiB (which means that there is more than one chunk), the eD2k hash is computed by concatenating the chunks' MD4 checksums in order and hashing the result again using MD4. Otherwise, the MD4 hash of the only chunk of the file is used with no further modifications.<ref>emule source, method <code>CKnownFile::CreateFromFile</code>.</ref>

This method of hashing allows the recipient to verify that a hash list corresponds to an original eD2k file hash, without the need to actually have the file present on disk.

In the past, there has been some ambiguity for files whose size is a multiple of the chunk size (9500 KiB). Old versions of some eD2k hash tools computed file hashes with an additional 0-byte chunk at the end. This is because an ambiguity of the term ''remainder chunk'' which can be interpreted as either ''the last chunk'' or a ''non-full chunk at the end''. Following the latter interpretation, some implementations added a zero byte chunk in case the last chunk of a file was a complete one. This practice is discouraged however and the first interpretation is used as a standard nowadays to prevent some files from having different hashes depending on the algorithm implementation used to calculate their hash.<ref>{{cite web|url=httphttps://mldonkey.sourceforge.net/Ed2k-hash|title=Ed2k-hash - MLDonkey|website=mldonkey.sourceforge.net|access-date=23 April 2018|archive-date=19 December 2017|archive-url=https://web.archive.org/web/20171219205033/http://mldonkey.sourceforge.net/Ed2k-hash|url-status=dead}}</ref>

=== AICH ===

{{main|eMule#Basic concepts}}

The AICH (Advanced Intelligent Corruption Handling) is an [[emule]]eMule extension. It subdivides the 9500 KiB chunk into 180-KiB blocks and builds a [[merkelMerkle tree]] out of the SHA1 hashes of the 53 blocks, so that the root hash of each block is called a ''block hash''. The block hashes further feed into a merkelMerkle tree, the root hash of which is the actual AICH root hash. The smaller block size allows eMule clients to more precisely identifify locations of corruption.<ref>{{cite web |title=Corruption Handling |url=http://www.emule-project.net/home/perl/help.cgi?l=1&rm=show_topic&topic_id=589 |website=www.emule-project.net}}</ref>

== Server links ==

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* [http://wiki.amule.org/wiki/Ed2k_link aMule wiki: ed2k link].

* [http://www.emule-project.net/home/perl/help.cgi?l=1&rm=show_topic&topic_id=422 emule project] Ed2k link formats supported by emule client.

* [httphttps://ed2k-tools.sourceforge.net/ed2k_hash.shtml ED2K tools - ED2K_Hash] Tool to create ED2K hashes.

* [http://phantomp2p.com Phantom P2P] eD2k Links Provider

{{URI scheme|state = uncollapsed}}