After completing this video, the learner will understand the basic concepts of cryptography, including encryption, decryption, keys and algorithms.
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- [Voiceover] Cryptography is one of the most important controls available to information security professionals. Encryption protects sensitive information from unauthorized disclosure in many different environments. And, many other security functions depend upon cryptography to function properly. So, what is cryptography? Cryptography is the use of mathematical algorithms to transform information into a form that is not readable by unauthorized individuals.
Cryptography does, however, provide authorized individuals with the ability to transform that encrypted information back into readable form. Cryptography depends upon two basic operations. The first, encryption, converts information from its plaintext form into an encrypted version that is unreadable. This is known as ciphertext. The second operation, decryption, performs the reverse transformation, using an algorithm to transform that encrypted ciphertext back into plaintext format.
I've used the term algorithm a couple of times. If you're not already familiar with algorithms, they are simply a set of mathematical instructions that one follows 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 that input through a series of steps. First, it subtracts 32 from the input, then multiplies the result by five, and divides that result by nine. This provides us with the output, the final result, which is the Celsius equivalent of the temperature that was input in Fahrenheit. Encryption algorithms work in similar ways, except the steps are a little different.
Encryption algorithms have two inputs. The first is P, the plaintext message, and the second is K, the encryption key. They then go through a series of steps that transform the plaintext using the key. I'll skip over the details of how encryption algorithms work for now, because we'll be discussing them extensively during the rest of this course. The encryption algorithm then has a single output, C, the ciphertext.
Decryption algorithms perform the reverse operation. They also have two inputs, the ciphertext message, and the decryption key, and they go through a series of steps that convert the ciphertext into plaintext using that decryption key. And, then, they return the plaintext message as output. Encryption and decryption are the two basic concepts of cryptography. I'm going to fill in the details throughout the rest of this course.
You'll see how different cryptographic algorithms use different steps and learn more about the roles of different types of cryptographic keys.
This course is part of a six-course series on the CompTIA Security+ exam, and is useful for IT professionals who wish to learn more about information security as well as students preparing to take the Security+ exam.
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- Choosing encryption algorithms
- Applying symmetric and asymmetric cryptography standards
- Implementing key management, including key exchange and key stretching
- Working with public keys, trust models, and digital certificates
- Using transport encryption protocols
- Securing wireless networks