In computer science, a hash collision is a random match in hash values that occurs when a hashing algorithm produces the same hash value for two district pieces of data.

One of the most popular methods used to secure the transmission of digital messages from being intercepted by third parties is through the use of hashing algorithms.

The hashing process provides the security layer necessary for securing the transmission of a message to its recipient. As a common practice in computer science, hashing is used for a variety of purposes including cryptography, data indexing, and data compression.

Hashing and cryptography make a perfect fit since both operate under the principle of protecting data by transforming it into a secure format. While cryptography uses a process called encryption, hashing uses a hash function which comprises a mathematical formula designed to truncate one value to another.

What is a hashing algorithm?

A hashing algorithm or function is a mathematical formula that takes a given input of data and generates a value with a fixed-length called a hash value. The hash value, therefore, acts as a summary representation of the original value.

For example, if you have a password for your computer that reads “Pass1234,” your computer will use a hash function to truncate that value by creating a hash value of a fixed size like this: “01.”

Think of a hash value as a series of numbered boxes ranging from 1 to 100. The password you enter can be a name card assigned to the first box. The stringed value of your password is protected since the computer only needs to locate the box with a matching hash value instead of remembering the string of letters in your password.

In our case, whenever you enter the password, “Pass1234,” your computer will verify whether that string of letters matches the hash value assigned to that input and therefore grant access.

Security is ensured as long as your password is the only input data producing the “01” hash value.

So what exactly is a hash collision?

A hash collision occurs when a hash algorithm produces the same hash value for two different input values.

For instance, a collision will occur if the hashing algorithm in our example above produces a hash value of “01” when you log in with the “Pass1234” password as well as when you insert a random value such as “pass.”

With such a collision, a bad actor can “trick” your computer into granting access erroneously by logging in with a password that is close enough to produce the same hash as your original password.

Conclusion: Types of hash algorithms.

Ideally, a good hash function should compute quickly while minimizing the possibility of producing the same hash value for two different inputs (collision). Programmers use different types of hash algorithms depending on the desired level of security.

Although the MD5 hashing algorithm was once one of the most popular hashing algorithms out there, it is now a compromised algorithm that readily generates collisions. Nowadays, the Secure Hash Algorithm (SHA-2 and SHA-3) family of hashing algorithms is considered the most secure.

Many programmers consider the best approach to be the use of the current hashing algorithms to prevent attackers from reverse engineering hash values.