What is Hashing?

Nowadays, hashing is a term that we are hearing more often. And no, this has nothing to do with hashtags...Hashing dates to the 1950s but gained prominence in the last 20th century. It plays a vital role in online safety in helping prevent the distribution of illegal content. Indeed, hashing is a process that takes an input and produces a fixed-size string of characters, which is typically a hash value or hash code. The primary purpose of hashing is to quickly index and retrieve items in a data set. Unlike conventional encryption, hashing is exclusively employed for one-way encryption, and deciphering hashed values is exceptionally challenging.

How exactly does hashing work?

1.      Hash Function

A hash function is mathematical algorithm that takes an input and produced a fixed string of characters, which is a hash value or cash doe. The same input will always produce the same hash output as it should be deterministic.

2.      Fixed size output

The hash function produces a fixed size output.

3.      Hash collisions

Hash functions aim to produce a unique hash for each unique input, but due to the finite size of the output, there is a possibility of two different inputs producing the same hash value. This is known as a collision.

Why do companies use hashing in the context of online safety?

1.      Content identification

Many companies use hashing in order to create unique fingerprints or hash values for specific content. This process is often used in technologies like PhotoDNA for image matching. The hash values represent the content in a way that is quick to compare and identify.

2.      Hash databases

Some platforms maintain databases of known hash values corresponding to illegal or harmful content such as CSAM. These databases are updated and shared with other platforms to help stop the spread of illegal content and enhance efforts in collective moderation.

3.      Proactive content moderation

If a user uploads a new content the platform creates a hash of that content and checks it against its database. If there is a match with a known illegal or harmful content hash the platform can then take immediate action.

4.      Privacy protection

Hashing enables platforms to detect illegal content without directly analysing or storing the actual content. This protects user privacy by not requiring the platform to view or store explicit material. It also enables platform to address harmful content without human moderators having to view explicit material directly.

5.      Legal compliance

Using hashing for content moderation helps platforms comply with legal requirements related to the prevention and reporting of illegal content.

Overall, hashing enables online platforms to contribute to a safer online environment by identifying and addressing the distribution of illegal & harmful content. Whilst hashing is an important tool online safety requires multiple different approaches and technologies in combination in order to be as effective as possible.