  Blockchain is a relatively new technology that can be seen as a decentralised
database. Blockchain systems heavily rely on cryptographic hash functions to
store their data, which makes it difficult to tamper with any data stored in
the system. A topic that was researched along with blockchain is image
authentication. Image authentication focuses on investigating and maintaining
the integrity of images. As a blockchain system can be useful for maintaining
data integrity, image authentication has the potential to be enhanced by
blockchain. There are many techniques that can be used to authenticate images;
the technique investigated by this work is image hashing. Image hashing is a
technique used to calculate how similar two different images are. This is done
by converting the images into hashes and then comparing them using a distance
formula. To investigate the topic, an experiment involving a simulated
blockchain was created. The blockchain acted as a database for images. This
blockchain was made up of devices which contained their own unique image
hashing algorithms. The blockchain was tested by creating modified copies of
the images contained in the database, and then submitting them to the
blockchain to see if it will return the original image. Through this experiment
it was discovered that it is plausible to create an image authentication system
using blockchain and image hashing. However, the design proposed by this work
requires refinement, as it appears to struggle in some situations. This work
shows that blockchain can be a suitable approach for authenticating images,
particularly via image hashing. Other observations include that using multiple
image hash algorithms at the same time can increase performance in some cases,
as well as that each type of test done to the blockchain has its own unique
pattern to its data.
