From the course: Exploring Tor and the Dark Web

Understanding encryption - Tor Browser Tutorial

From the course: Exploring Tor and the Dark Web

Start my 1-month free trial Buy for my team

Understanding encryption

“

- [Instructor] Cryptography is one of the most important controls available to cybersecurity professionals. Encryption protects sensitive information from unauthorized disclosure in many different environments, and many other security functions depend upon cryptography, including the Tor network. So before we dive into the technology behind Tor, let's quickly cover some basic cryptography. Cryptography is the use of mathematical algorithms to transform information into a form that's not readable by unauthorized individuals, but provides authorized individuals with the ability to transform that information back into readable form by again using a mathematical algorithm through decryption. Cryptography depends upon two basic operations. The first, encryption, converts information from its plaintext form into an encrypted version that is unreadable, also known as ciphertext. The second operation, decryption, performs the reverse transformation using an algorithm to transform encrypted information back into plaintext form. Now, I've used the term algorithm a few times. If you're not already familiar with algorithms, they're just a set of mathematical instructions that you can follow to achieve a desired result. Think of an algorithm as a mathematical recipe. Algorithms are very similar to computer code, and in fact, computer code is often designed to implement mathematical algorithms. Let's take a look at a basic algorithm designed to convert temperatures from Fahrenheit into Celsius. The algorithm has an input the temperature in Fahrenheit, and then it takes this input through a series of steps. First, it subtracts 32 from the input, then it multiplies the result by five and divides that result by nine. Then it provides the final result as output, which is the Celsius equivalent of temperature that was input in Fahrenheit. Encryption algorithms work in similar ways, except the steps are different. They have two inputs, the plaintext message and an encryption key. Then they go through a series of mathematical steps that transform that message using the key. The important thing to know is that these steps are complex and the use of a strong encryption key makes them impossible to reverse without access to the key. The output of the process is an encrypted message. If you were to open up this message, you'd find that it's no longer readable to the human eye. It would just look like a bunch of digital garbage. When you do need to reverse the encryption operation and access the original data, you do so using a decryption function. Decryption functions also have two inputs, the encrypted message, otherwise known as the ciphertext and the decryption key. The function then uses the decryption key to follow another series of complex mathematical steps on the ciphertext message. These steps reverse the encryption process and restore the original data. It's important to note that you can't decrypt a message without access to the appropriate decryption key. Protecting the secrecy of the decryption key preserves the security of the encrypted data. The output of the decryption process is the plaintext data. And that's how encryption and decryption work.

Contents