Popularize SHA1, ed2k link related knowledge

A few days ago, Microsoft opened the official version of Win8.1 image download to MSDN subscribers, but after user comparison, it has been confirmed that the image is completely consistent. So here Xiaobian tells everyone that you have downloaded the leaked image and don't download it again. However, there are always many friends who have obsessive-compulsive disorder. It is not comfortable without re-downloading them. Do you have such obsessive-compulsive disorder? Let's take a look at SHA1, ed2k related knowledge, to see if the above is said that Microsoft is open and the same leaked before, after reading the following article you will know the reason. =========================================================== = Little knowledge 1: What is the hash of the file? What is SHA1? What is the role? The file hash value —— we can simply understand it as: a string of characters obtained by calculating the file data using a special algorithm. There are many such algorithms. For each algorithm, a file corresponds to a unique hash value, but not necessarily the other way around. However, for a good algorithm, because its backward estimation is almost impossible to achieve, it is almost impossible to forge a file with the same hash value based on the hash value of a file (and this file can still have The original file has the same function), so we think that the same file with the hash is the same file, and it is completely possible to judge the correctness and completeness of the file based on the hash value. Commonly used file hashing algorithms are: MD2, MD4, MD5, SHA1, and so on. People often judge the authenticity or integrity of a document based on the MD5 and SHA1 of the file. For specific methods, please refer to "Why check, how to verify". Many friends don't believe in the theory of file hashing, but they are waiting for a download link called ed2k. As everyone knows, the eD2k link itself is based on a hash of the file, and with the leaked version of the image we actually have the ed2k download link for this file. Let's take a look at it. Tip 2: How is the ed2k link generated? —— Science downloads are downloading all kinds of things every day —— movies, games, software, anime … … ed2k is one of our more common types of download links. But have you ever seen, what happened to us when we downloaded an ed2k linked file to the computer? It is not difficult to know the mystery. Let's start with the generation of ed2k links. Take a closer look at the ed2k link form and you'll see that these links follow a specific format. For a file resource its basic ed2k link form is: ed2k://| File| Aa….aa| Bb…..bb| Cc……cc| /Where “aa….aa” part indicates the file name, which can be changed at will; "bb…..bb” part indicates the file size (bytes); the most critical is the "cc……cc". The cc……cc” part is actually a hash of the file (ie ed2k hash algorithm, a variant of the MD4 algorithm). To put it bluntly, the basic form of the ed2k link is actually a combination of several sets of file information. Because the file hash value is unique, the ed2k share link of a file is actually uniquely determined since the file was born, and the leaked image and the image issued by Microsoft to the MSDN user are identical, so the two ed2k links It is also the same. Note that the file name can be changed at will, which will not affect the final download result (remember to download the gourd XX as a farce?). It is precisely because a file's ed2k link is unique, so for some public resources its ed2k link publisher and resource sharer may not be the same person, we would also like to thank those who are silently sharing behind us. (You may be one of them. Here, Xiaobian also applauds himself ((*∩_∩*)) So how does the ed2k link come about? Very simple, as long as you download the authentic eDonkey client (using foreign. The basics of the country have become pitted), put the files on your computer into the shared directory will automatically generate the ed2k share link of the file. Or you can use the hash calculation software to calculate the ed2k hash of the file, and then combine it to get the ed2k link address. Here are two softwares, hashcalc and LinkCreator. The former can calculate the ed2k hash of the file (as shown below, 32-bit Win8.1 retail image ed2k hash), which can directly generate the ed2k link of the file. Where is the file from? ——ed2k All National Network Archives We know that we can generate ed2k links for any file in our computer through the principle of the ed2k link. Ok, now that the link is there, then where did we get the file when we downloaded the file? This requires a brief look at how the ed2k network works. Finally, we need to consider China's national conditions. Ed2k network: ed2k network is a file sharing network that all netizens can participate in. You only need to download a eDonkey client to download files from ed2k network or share files on your own computer to ed2k network. The basis for identifying files when downloading or sharing files in the ed2k network is the ed2k link (that is, the file hash). When you download a file, the file is divided into a number of clips to download: you get the parts they have downloaded from other people's computers, and you also upload the downloaded parts to others. However, domestic software such as Thunder and Whirlwind is not a pure ed2k client. Even if you use the ed2k link when downloading files, the file source will not all come from the ed2k network. Because Thunder will identify the file based on the ed2k hash of the file, then it can get resources from multiple sources (Thunderbolt, offline, mirror download, P2P, etc.). For the more popular resources, Thunder has mastered a variety of access to this file, so you can calculate the ed2k link of a popular file to publish it to the network, even if you do not do it, you can let others download it. Network disk sharing, or ed2k and other download methods are based on the file hash algorithm to identify the file. When uploading a file on the network disk, it will first calculate the hash of the file. If the file already exists, the file will be transmitted twice, so no matter who uploads it, the shared link points to the same file, but the name changes. The ed2k link only recognizes the hash value, and the file name does not affect the download; therefore, even if someone re-shares the MSDN original image, there is no difference in the source of the file data when downloading the file, and the download result is naturally the same. The above is a brief introduction to SHA1, ed2k. Understand the above knowledge, do you still have obsessive-compulsive disorder? ==================================================================================================== Participate, after downloading the client, you can get the server list here, and then import the list into the client to connect to the ed2k network. The server is responsible for linking the clients that download and share the same file, while providing a search function for the resources. Clients can also rely on Kad to do this, and Kad is trying to weaken the role of the server. The ed2k network is an open file sharing network. Clients participating in the ed2k network should abide by the GPL. The search and download should be unrestricted, so that every user can enjoy free and equal rights in use. Some excellent foreign clients follow this agreement, and there is no limit to the use of these client users. Ed2k is certainly a good thing, but it is in our great motherland, because the participation of commercial companies has changed. This is also determined by our national conditions. Netizens do not share the spirit and consciousness. Commercial companies are profit-seeking, and the upstream and downstream bandwidth are not equal. … … Some examples: Is this not the case? I believe that many of my friends have used a famous eDonkey downloading software in China. It is necessary to know that this software not only violates the open source agreement, but also imposes many restrictions on the software, so it has been dubbed by many informed users as “阉阉驴” or ““ False 驴 & rdquo; and so on. For details, please refer to the "VeryCD easyMule v1.1.15 official version introduction review", and will not repeat them. Why is Thunder called a vampire?

So, why is Thunder called a vampire? This is because it violates the GPL agreement, which only gets unshared in the ed2k network, or only preferentially uploads to the Thunder client users. So people who love sharing are called vampires. P2Pxxxxx——The seed search artifact is not God? As mentioned earlier, the authentic ed2k client search resources are completely unrestricted. Therefore, searching for artifacts is not really magical. On the contrary, these clients that only send search requests to the server, but never actively share resources, can only be a burden to the server, and do not contribute to the ed2k network. For some reason, this has led to the consequences of foreign servers deciding to block domestic IP.