Hashing is a process that uses an algorithm (such as MD5, SHA-1 or SHA-2) to create a unique identifier – a ‘hash’ – for a file on the basis of its data. Two identical files will always have the same hash. Likewise, two different files will always have different hashes, even if the difference between the two files is minimal. The hashes of files found to infringe copyrighted material can be added to ‘black lists’, which can be used by cloud storage services to detect, block and take down unauthorised files.
Used for
Authentication
Goes on
Product
Can be used for
Digital products
Visibility
Invisible
Reading device needed
Yes
Connection to server
Yes
No
Description
The purpose of hashing is to identify different copies of the same digital file. First, an algorithm is used to assign a unique string of characters, called a ‘hash’, to the digital file, and that hash is stored in a hash database. A second digital file is then put through the same hashing process, and the resulting hash is compared with the one already stored in the hash database to determine whether the files match exactly.
Uses
Hashing is primarily used to index content, secure passwords, detect malicious files such as viruses, or block illegal content, such as the promotion of acts of terrorism or exploitation of minors. With respect to copyrighted material, hashes serve to identify, compare and prevent the upload of digital content that has already been taken down due to copyright infringement.
Implementation
It is difficult to provide specific implementation requirements for hashing as there are several different hashing techniques and algorithms that can be used, all of which require different amounts of computational power. Most hashing methods are cryptographic (in which two different files, although very similar, will have completely different hashes) but perceptual hashing methods also exist (in which two almost identical files, for instance similar images, will have similar hashes). That said, the advantage of hashing is that it can be applied to already existing content. Hashes can be shared and used by all the different parties using the same hashing process and the same hash database. The disadvantage, however, is that hashing only recognises the same identical file, not its content.
Cost
Hashing requires limited investment as open source solutions are available. Furthermore, as hash databases only store a string of characters rather than the entire file, they require fewer computational and memory resources.