What is a hash and what is it for?

Within blockchain technology, there are a series of specific terms, such us smart contracts, which we do not want you to miss out on. In this video, our Blockchain Expert, Diego González, talks about hashes. He explains what they are and how useful they are.

A hash is a “fingerprint”, that allows us to identify the content of a file in a simple sequence of characters.

This sounds a little strange but basically what it means is that, regardless of the size of a file, its hash will always have a certain length, which allows you to publish a unique identifier, an alphanumeric sequence, which represents the content of the file, a fingerprint that identifies all of its content, in a simple line of text, without having to have a lot of disk space or having to publish confidential information, associated with the content of that file.

In other words, the hash is a sequence that can be calculated from the contents of a file but not the other way around. That is, it is impossible to get the contents of a file from a hash. It does not compromise the data contained in the file.

Calculating the hash of a file is as simple as applying a mathematical function, a computer function. A program that complies to a standard and performs certain operations on the content, the bytes of the file, and what it returns is a brief sequence of letters and numbers. If we apply the same function to calculate the hash different times on the same file, the result will be the same, the hash will not change. However, if we apply the function to a file after modifying it, it would give us a different result. The utility can be seen there, in the fact that it allows us to distinguish when an original file is still as it was at the beginning or when it has been modified.

Let’s imagine that we have a file: a photograph, a video or a PDF. We send our file to someone by mail and we want to delete it from our computer because it takes up a lot of space. But we would like a year later to have the file returned to us as it was, and we want to check that nothing has changed. That they haven’t removed part of the video, they haven’t manipulated the photograph, they haven’t put a new text in our spreadsheet… We want to check that they return it to us just as we sent it to them. How do we do this if we no longer have the original file to compare it to because we have deleted it from our hard drive? If we calculated the hash and wrote it down on a piece of paper or saved it in a text file, all we have to do is recalculate the hash of the file they’ve sent us and we will be able to check and verify that nobody has modified it.

What is the use of this for us in the field of blockchain technologies?

In our case, Docuten calculates the hash both of the documents that are signed on our platform and of the invoices that are sent through it, and what we do is to include that hash in our Smart Contracts, including this hash together with information related to document creation dates, historical events, which allow us to identify or trace the life cycle of documents or invoices. This information is published on the blockchain without compromising confidential data that was contained in the original file.

This allows us to certify the existence of invoices and documents but we do not compromise confidential data.

At the same time, we minimize data storage on the blockchain. There is no point in uploading an entire PDF when we just want to certify that it existed.

As we have already told you in our blog, in Docuten we use blockchain technology for the certification of documents and invoices. Contact us for more information.

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