Asymmetric Encryption

Posted by in Security+ | 0 comments

This is part 2 of the Symmetric and Asymmetric Encryption blog post. You can see part 1 here.

Asymmetric Encryption

Asymmetric encryption uses two keys in a matched pair to encrypt and decrypt data—a public key and a private key. There are several important points to remember with these keys:

  • If the public key encrypts information, only the matching private key can decrypt the same information.
  • If the private key encrypts information, only the matching public key can decrypt the same information.
  • Private keys are always kept private and never shared.
  • Public keys are freely shared by embedding them in a certificate.

Remember this

Only a private key can decrypt information encrypted with a matching public key. Only a public key can decrypt information encrypted with a matching private key. A key element of several asymmetric encryption methods is that they require a certificate and a PKI.

Some examples of asymmetric encryption are:

  • RSA
  • Diffie-Hellman

CompTIA Security+ Study Guide (SY0-401)

The 401 Version of the Study Guide is Now Available

SY0-401 Study GuideThe CompTIA Security+: Get Certified Get Ahead: SY0-401 Study Guide is an update to the top-selling SY0-201 and SY0-301 study guides, which have helped thousands of readers pass the exam the first time they took it.

CompTIA Authorized Quality Content (CAQC)After a comprehensive review by ProCert Labs, the SY0-401 version has been certified as CompTIA Approved Quality Content (CAQC) and covers every aspect of the SY0-401 exam.

It includes the same elements readers raved about in the previous two versions.

Each of the eleven chapters presents topics in an easy to understand manner and includes real-world examples of security principles in action.

You’ll understand the important and relevant security topics for the Security+ exam, without being overloaded with unnecessary details. Additionally, each chapter includes a comprehensive review section to help you focus on what’s important.


Click for Free Preview


Over 400 realistic practice test questions with in-depth explanations will help you test your comprehension and readiness for the exam. The book includes:

  • A 100 question pre-test
  • A 100 question post-test
  • Practice test questions at the end of every chapter.

Each practice test question includes a detailed explanation to help you understand the content and the reasoning behind the question. You’ll be ready to take and pass the exam the first time you take it.

If you plan to pursue any of the advanced security certifications, this guide will also help you lay a solid foundation of security knowledge. Learn this material, and you’ll be a step ahead for other exams. This SY0-401 study guide is for any IT or security professional interested in advancing in their field, and a must read for anyone striving to master the basics of IT security.

Kindle edition also available.

Asymmetric Encryption to Privately Share a Key

Although asymmetric encryption is very strong, it is also very resource intensive. It takes a significant amount of processing power to encrypt and decrypt data, especially when compared with symmetric encryption. Most cryptographic protocols that use asymmetric encryption only use it to privately share a symmetric key. They then use symmetric encryption to encrypt and decrypt data because symmetric encryption is so much more efficient.

Some of the more advanced topics related to asymmetric encryption become harder to understand if you don’t understand the relationship of matched public and private key pairs. However, because you can’t actually see these keys, the concepts are hard to grasp for some people. The Rayburn box demonstrates how you can use physical keys for the same purposes as these public and private keys.

The Rayburn Box

I often talk about the Rayburn box in the classroom to help people understand the usage of public and private keys. A Rayburn box is a lockbox that allows people to securely transfer items over long distances. It has two keys. One key can lock the box, but can’t unlock it. The other key can unlock the box, but can’t lock it.

Both keys are matched to one box and won’t work with other boxes:

  • Only one copy of one key exists—think of it as the private key.
  • Multiple copies of the other key exist, and copies are freely made and distributed—think of these as public keys.

The box comes in two different versions. In one version, it’s used to send secrets in a confidential manner to prevent unauthorized disclosure. In the other version, it’s used to send messages with authentication, so you know the sender actually sent the message and that the message wasn’t modified in transit.

Get Certified Get Ahead

The Rayburn Box Used to Send Secrets

Imagine that I wanted you to send some proprietary information and a working model of a new invention to me. Obviously, we wouldn’t want anyone else to be able to access the information or the working model. I could send you the empty open box with a copy of the key used to lock it.

You place everything in the box and then lock it with the public key I’ve sent with the box. This key can’t unlock the box, so even if other people had copies of the public key that I sent to you, they couldn’t use it to unlock the box. When I receive the box from you, I can unlock it with the only key that will unlock it—my private key.

This is similar to how public and private keys are used to send encrypted data over the Internet to ensure confidentiality. The public key encrypts information. Information encrypted with a public key can only be decrypted with the matching private key. Many copies of the public key are available, but only one private key exists, and the private key always stays private. The “Understanding the HTTPS Process for Security+” post shows this process in more depth.

Security+ Practice Test Questions

SYO-401 Practice Test Questions Now Available

Over 440 realistic Security+ practice test questions

All questions include explanations so you'll know why the correct answers are correct,

and why the incorrect answers are incorrect.

Pass the Security+ Exam

the First Time You Take It

Multiple quiz formats to let you use these questions based on the way you learn.
  • Learn mode - randomized. View each of the questions in random order. Learn mode allows you to keep selecting answers until you select the correct answer. Once you select the correct answer, you'll see the explanation. Click here to see how learn mode works.
  • Learn mode - not randomized. View each of the questions in the same order. Use this if you want to make sure that you see all of the questions. Learn mode allows you to keep selecting answers until you select the correct answer. Once you select the correct answer, you'll see the explanation. Click here to see how learn mode works.
  • Test mode - randomized. View each of the questions in random order. In test mode, you can only see the correct answers and explanations after you complete the test. Click here to see how test mode works.
  • Test mode - not randomized. View each of the questions in the same order. In test mode, you can only see the correct answers and explanations after you complete the test. Click here to see how test mode works.
  • Test mode - 100 random questions. View 100 random questions from the full test bank similar to how the Security+ exam has a potential maximum of 100 multiple choice questions. In test mode, you can only see the correct answers and explanations after you complete the test. Click here to see how test mode works.

Get the full bank of Security+ Practice Test Questions Here

 SYO-401 Practice Test Questions Now Available


INCLUDES QUESTIONS TO HELP YOU PREPARE

FOR THE NEW PERFORMANCE BASED QUESTIONS 

Bonus - Performance Based Questions

Additional Security+ questions to help you prepare for the new performance based questions. These are included with the full bank of Security+ practice test questions and are divided into different sections. For example, you'll have access to the following links:

- Performance Based Question - Set 1

You'll see a graphic explaining what you might be required to do on the actual exam to match different types of security to mobile devices and servers in a data center. You'll then have two questions that test your knowledge and ability to correctly answer the questions. This question also includes a link to a graphic showing the end solution for the overall performance based question simulation.

- Performance Based Question - Set 2

You'll see a graphic explaining what you might be required to do on the actual exam to match different types of attacks with the name of the attack type. You'll then have five questions that test your knowledge and ability to correctly answer the questions. This question also includes a link to a graphic showing the end solution for the overall performance based question simulation.

- Performance Based Question - Set 3

You'll see a graphic showing a network with computers and servers separated by a firewall. The firewall is used to control traffic between the computers and users using rules within an access control list (ACL).  You'll have three questions that test your knowledge and ability to correctly identify the relevant components of the rule. The incorrect answers and explanation provide you with insight into how to correctly answer this type of question on the actual exam.

- Performance Based Question - Set 4

You'll see a graphic explaining what you might be required to do on the actual exam related to what a forensic analyst would do during an investigation. You'll then have two questions that test your knowledge and ability to correctly answer the questions. This question also includes a link to a graphic showing the end solution for the overall performance based question simulation.

- Performance Based Question - Set 5

You'll see a graphic explaining what you might be required to do on the actual exam to match protocols and ports. You'll then have seven questions that test your knowledge and ability to correctly answer the questions. This question also includes a link to a graphic showing the end solution for the overall performance based question simulation.

- Performance Based Question - Set 6

You'll see a list of security controls along with a graphic showing devices and locations within an organization, along with instructions on what you might be required to do on the actual exam to match the controls with the devices and locations. You'll then have four questions that test your knowledge and ability to correctly answer the questions. This question also includes a link to a graphic showing the end solution for the overall performance based question simulation.

- Performance Based Question - Set 7

You'll see a list of authentication methods and authentication factors along with instructions on what you might be required to do on the actual exam to match the authentication methods with the authentication factors. You'll then have six questions that test your knowledge and ability to correctly answer the questions. This set also includes a link to a graphic showing the end solution for the overall performance based question simulation.

- Performance Based Question - Set 8

You'll see a graphic explaining what you might be required to do on the actual exam to match different types of attacks with the name of the attack type. You'll then have five questions that test your knowledge and ability to correctly answer the questions. This is similar to Set 2 but expands on the possibilities. The set also includes a link to a page showing the end solution for the overall performance based question simulation.

New - Performance Based Question - Set 9

New questions recently added using a different testing engine. See a demo here. This set includes drag and drop and matching questions on ports.

New - Performance Based Question - Set 10

A random set of 20 performance-based questions using drag and drop, matching, sorting, and fill in-the blank. This set includes performance-based questions on RAID.

Get the full bank of Security+ Practice Test Questions Here

Get the full bank of Security+ Practice Test Questions

The Rayburn Box Used for Authentication

With a little rekeying of the box, I can use it to send messages while giving assurances to recipients that I sent the message. In this context, the message isn’t secret and doesn’t need to be protected. Instead, it’s important that you know I sent the message.

When used this way, the private key will lock the Rayburn box, but it cannot unlock the box. Instead, only a matching public key can unlock it. Multiple copies of the public key exist and anyone with a public key can unlock the box. However, after unlocking the box with a matching public key, it isn’t possible to lock it with the public key.

Imagine that you and I are allies in a battle. I want to give you a message of “SY0-401,” which is a code telling you to launch a specific attack at a specific time. We don’t care if someone reads this message because it’s a code. However, we need you to have assurances that I sent the message.

I write the message, place it in the box, and lock it with my private key. When you receive it, you can unlock it with the matching public key. Because the public key opens it, you know this is my box and it was locked with my private key—you know I sent the message.

If someone intercepted the box and opened it with the public key, he or she wouldn’t be able to lock it again using the public key, so you’d receive an open box. An open box with a message inside it doesn’t prove I sent it. The only way you know that I sent it is if you receive a locked box that you can unlock with the matching public key.

This is similar to how digital signatures use public and private keys. The “Understanding a Digital Signature” post explains digital signatures in more depth. In short, I can send you a message digitally signed with my private key. If you can decrypt the digital signature with my matching public key, you know it was encrypted, or signed, with my private key. Because only one copy of the private key exists, and I’m the only person who can access it, you know I sent the message.

The Rayburn Box Demystified

Before you try to find a Rayburn box, let me clear something up. The Rayburn box is just a figment of my imagination. Rayburn is my middle name.

I haven’t discovered a real-world example of how public/private keys work, so I’ve created the Rayburn box as a metaphor to help people visualize how public/private keys work. Feel free to build one if you want.

Check out these free practice test questions for symmetric and asymmetric encryption.

Leave a Comment

CompTIA Security+: Get Certified Get Ahead: SY0-401 Study Guide

Subscribe To Our Newsletter

Join our mailing list and get a free excerpt of the CompTIA Security+: Get Certified Get Ahead: SY0-401 Study Guide.  This excerpt includes the introduction and Chapter 1. 

You have Successfully Subscribed!

Get Certified Get Ahead is a participant in the Amazon Services LLC Associates Program,
an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to amazon.com.

Copyright © 2015 Get Certified Get Ahead. All Rights Reserved.