Trending February 2024 # Yubico 5C Nfc Security Key Has Usb # Suggested March 2024 # Top 10 Popular

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Yubico 5C NFC security key has USB-C and wireless in one

Yubico has revealed its latest hardware security key, with the YubiKey 5C NFC combining USB-C and NFC support for easier authentication. Billed as the top request from the company’s users, the newest key looks like a thumb drive but is actually a cross-platform way to make sure it’s you that’s logging into your various accounts.

That means support for FIDO2 and WebAuthn, FIDO U2F, PIV (smart card), OATH-HOTP and OATH-TOTP (hash-based and time-based one-time passwords), OpenPGP, YubiOTP, and challenge-response. The YubiKey 5C NFC is compatible with Windows, macOS, iOS, Android, and Linux.

Out of the gate it’ll work with services like 1Password, Basecamp, Citrix Workspace, Dropbox, and your Google Accounts. Don’t assuming it’s just for work or school, mind: Yubico also has support for Epic Games, EVE Online, EA, and your Nintendo account, for instance. On the social networking side, you can use it to gain access to your Facebook, Instagram, Reddit, or Twitter account.

As with other Yubico models, you can authenticate by plugging the key into a device with a USB-C port. That way, if the YubiKey 5C NFC isn’t present, your accounts are locked down. However you can also tap it against NFC-compatible devices, like recent iPhones and many Android phones.

Yubico says that, compared to a one-time passcode sent out by SMS, or by pulling up a code from a mobile authenticator app, the YubiKey 5C NFC can be up to four times faster at getting you logged in. It’s also counting on a big uptick in working from home and home-schooling to drive adoption of more secure – but also swifter – account management tools.

On the enterprise side, there’s the promise of easy at-scale deployment of the key, including the ability to have them shipped directly to employees at home. For personal users, there’s a long list of supported platforms and accounts that can be used with the key.

As for the design itself, it’s scaled to fit neatly on a keyring and doesn’t require batteries or charging. It’s narrow enough that you can plug it into a MacBook Pro’s USB ports and still have space for the official Apple USB-C power cable connected alongside it. Setup is relatively straightforward too: go to the service you want to use your YubiKey with – there’s a direct link to the installation process for each supported platform from Yubico’s site – and follow the short instructions list.

Usually it’s a case of logging in the way you have been so far, plugging in the key and tapping it, or tapping it against the device when requested, and then if you want access in future you’ll need to insert the key or tap it against the NFC device. There’s also a one-time passcode generator app, available for desktop and mobile. That will only show the limited-time passcodes after authenticating with the key.

The downside to all this is price. While you can pick up a Google Titan Security Key from $25, the YubiKey 5C NFC is available from today at $55. Those particularly aware of their data security may well be able to easily justify the extra expense, though frankly everyone could probably benefit from some sort of security key whether it’s this flagship example or something more mainstream.

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Fix: Registry Editor Could Not Set Security Key Currently Selected

Registry Editor could not set security key or some subkeys






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Registry Editor could not set security key currently selected or some of its subkeys the error message you get when you work with protected registry keys or subkeys. The protection of the Windows Registry is not a fault; it is protected by default and only editable by the Windows system itself.

To resolve this issue, we will change the security permissions for the Windows registry keys and subkeys. This guide deals with the Windows Registry Editor. Follow the steps carefully to avoid complications.

How do I fix the Registry Editor could not set security key currently selected error? 1. Start your computer in Safe Mode

Go to Settings on your computer by pressing the Windows logo key and then I on your keyboard.

Next, hit Restart now under Advanced startup.

Here, go to Troubleshoot.

On the next window, select Advanced options.

Finally, hit Restart.

This restarts the computer. When it comes back on, this time, press the F4 key or choose 4.

This puts the computer in Safe Mode and troubleshoots the registry editor could not set security in the key selected error. To exit Safe Mode after fixing this error, restart your machine or follow the steps below:

Press the Windows logo key and then R on your keyboard. This opens the Run box.

In Run, enter msconfig and hit

Finally, uncheck Safe boot. This you can find in the Boot options.

2. Enable the built-in Admin user account

Expert tip:

Press the Windows logo key to open the Start menu.

In the Command Prompt window, enter the command below and hit Enter:

net user administrator /active:yes

Next, type exit in command prompt and press Enter to close the window.

Now, log out of the Administrator user account.

3. Set registry key permissions

Open the Run dialog box by pressing the Windows logo key and R on your keyboard.

Enter regedit in the box and hit OK to open Registry Editor.

In Registry Editor, navigate or enter the path to the relevant key.

To claim ownership of the key and its subkeys, type in your user account name and hit Check Names.

The name you entered now changes to the official username. Mark the Replace owner on subcontainers and objects checkbox.

You have successfully claimed ownership of the registry key. However, you have to also change the permission of the keys to remove the registry editor could not set security in the key selected error.

3.1 Change registry key permissions

Next, hit the Add button to include yourself.

In Basic permissions, Mark the Full Control checkbox and hit OK.

You are then returned to the Advanced Security Settings dialog box. At the bottom of the screen, check to Replace all child object permission entries with inheritable permission entries from this object.

The Windows registry is a sensitive space because it contains files that control the working of everything on the computer. Because of this, strict restrictions are in place to prevent modification, deleting, or even accessing the keys and subkeys.

To fix the Registry Editor could not set security key currently selected or some of its subkeys error you get on the system, you have to assign yourself rights to it using the guides here. Lastly, remember to either back up the keys or create a system restore point before attempting this fix.

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What Is A Network Security Key? Definition & How To Find It

A network security key is a network password that is used to provide access and authorization on a device or network so a user can join.

The key provides a secure connection between the user and the wireless device, such as a router. Without a key system as a roadblock, cybercriminals could access the network and possibly commit a cybercrime.

Read below to see how it works, the difference between network security types, and how to find network security keys for important devices:

For more information on network security: How to Conduct a Network Security Risk Assessment

Should You Ever Change Your Network Security Key?

A network security key is physical, digital, or biometric data that allows a user to connect to a private network. Typically it is a Wi-Fi or wireless network password.

Network security helps you to ensure that the network is secure. Private networks, such as business or home networks, need to keep hackers or unwanted users out of their systems.

Devices like smartphones, tablets, and laptops connect to the network security key to access Wi-Fi, so it is often referred to as a Wi-Fi password. Connections can be set up through a device’s settings, helping the task stay simple for non-experts.

For more on network security: Develop & Implement a Network Security Plan in 6 Easy Steps

The most well-known and widely used types of network security keys are WEP, WPA, and WPA2:

WEP is the oldest and considered outdated

WPA is a newer key with some issues

WPA2 is the newest and built to prevent the main WPA and WEP problems

WEP (wired equivalent privacy) is a standard network security key protocol that adds security to Wi-Fi and other wireless networks. WEP was designed to give wireless networks the level of privacy protection a wired network provides. 

WEP uses encryption based on a combination of user and system-generated key values. Originally, WEP supported encryption keys of 40 bits plus 24 bits of system-generated data, making the keys 64 bits in total length. Now as an updated network security key, the encryption keys have been extended to support 104-bit, 128-bit, and 232-bit encryption keys. 

WEP encrypts the data a company uses, making the keys unreadable to a human, but is processed through receiving devices. Many tech experts recommend against WEP, as it is now considered outdated.

WPA (Wi-Fi Protected Access) was created to be the Wi-Fi Alliance’s replacement for WEP. WEP provides authorized systems with the same network security key, while WPA uses the temporal key integrity protocol (TKIP), which actively changes the key that a company or consumers use. 

WPA includes integrity checks to determine if a cybercriminal had stolen data packets. The keys used by WPA can support up to 256-bit, but certain elements of WPA can be exploited.

A WPA key is a network security key that connects to a wireless network. Whoever has access to the WPA password can give the key to employees or consumers. Some wireless routers will have the default WPA passphrase or password.

WPA2 is an upgraded version of WPA. WPA2 is based on the robust security network (RSN) mechanism, and it works in two modes:

Personal mode or Pre-shared Key (WPA2-PSK)

: Usually used in consumers’ homes, WPA-PSK uses a shared password for access. 

Enterprise mode (WPA2-EAP)

: Used by enterprises or businesses, the password is usually only accessible through another administrator.

CCMP (Counter Mode Cipher Block Chaining Message Authentication Code Protocol) is used by both modes and is based on the Advanced Encryption Standard (AES) algorithm. This offers message authenticity and integrity verification. 

However, like WEP and WPA, WPA2 has flaws. Attackers can exploit a system weakness in WPA2, allowing attackers to pose as another network and make the user connect to a fake and dangerous network. Hackers could decrypt encryption keys. Still, WPA2 is thought of as more secure than WEP or WPA.

For more information on network security: What is Network Detection and Response? 

Each different device has its own way to connect to a network security key. Familiar devices, such as smartphones and computers, will connect through the Wi-Fi network. Once connected, the device should remember the network security key. 

Routers and modems often have network security on them, or if used as a business key, an administrator will likely have access to the password.

For more details on how to find the network security key, see below:

Each ISP (Internet service provider) and the manufacturer will likely use different phrasing, so if there is a sticker on the router, it might be phrased differently than the network security key.

Here are some names ISP and manufacturers might use for network security keys:


Network Key

Wireless password

WPA or WPA2 key

Occasionally, an ISP or manufacturer might require a user to go to their account settings for the network security key. Once the router has been identified and the network security key is on the hardware or given to a user, a connection for users will be available.

Finding a network security key for Android and iPhone takes little time. Additionally, these two platforms will have slightly different steps. Updates on the devices have the potential to change the process.

Tap the “i” icon next to the network.

Enter or find the router’s login credentials.

Type in the password to connect.

Select the current network.

Scan the QR code or see the router to find the Wi-Fi password.

In the Network and Sharing Center, next to Connections, select your Wi-Fi network name.

In Wi-Fi Status, select Wireless Properties.

In Wireless Network Properties, select the Security tab, then select the Show characters check box.

A user’s Wi-Fi network password is displayed in the Network security key box.

Open the search function.

Search keychain access.

In the Keychain Access screen, search for the Wi-Fi network.

Check Show Password to make the network security key visible.

Enter the Mac password to confirm user access rights.

Network security key mismatch errors can be frustrating for businesses and consumers. There is not one specific answer for a mismatch error. However, the top three reasons this might happen are:

Wrong security mode

: A user’s device might be under a different security type or the device remembers its user as a certain security type. If this does happen, a user can go into network settings and change the security type.

Third-party antivirus tools

: While antivirus tools are essential for cybersecurity, third-party tools might cause connection issues. They can affect how the Wi-Fi passwords are stored. If this is the case, the antivirus tools may need to be uninstalled.

Old or faulty wireless drivers

: The user’s wireless drivers can cause mismatch errors as well. An old or faulty wireless driver may not have the same tech or connection, making it difficult to make changes to the network. If this is the case, tech experts recommend getting newer wireless drivers or updating the driver. 

It is vital to try different commands and other forms of updating if the top mismatch errors are not helpful. 

Changing the network security key is recommended, due to its importance. To keep a system safe, it is almost necessary to do it every 6 to 12 months.

A company’s or user’s computer is needed to change a network security key, but it only requires a little bit of computer knowledge. The process depends on the router’s brand and model, but commonly works with the directions below: 

Finding the Router’s IP Address

Type “ipconfig /all“ and press enter. A user will be given details about the router connection. Once the details are up, a user needs to look for the “default gateway” and write down the IP address. 

Open the web browser and type the IP address. The router will require a username and password that can generally be found on the router’s web management interface. Once access is given, a user may want to change their credentials for security purposes.

Network security keys are vital for any user or company with a private network. Cybercrime, uninvited users, and hackers can be prevented through network security keys.

Whether devices are using WEP, WPA, or WPA2 types, protection is necessary within network connections. Changing the password is a necessary step as well, to save any worry about unsafe networks.

Also see: Why Firewalls are Important for Network Security 

Difference Between Primary Key And Foreign Key

Key Differences between Primary Key vs Foreign Key

A primary key constraint is a column that uniquely identifies every row in the table of the relational database management system, while a foreign key is a column that creates a relationship between two tables.

The primary Key never accepts null values, whereas the foreign key may accept multiple null values.

You can have only a single primary key in a table, while you can have multiple foreign keys in a table.

The value of the primary key can’t be removed from the parent table, whereas the value of foreign key value can be removed from the child table.

No two rows can have any identical values for a primary key; on the other hand, a foreign key can contain duplicate values.

There is no limitation in inserting the values into the table column while inserting any value in the foreign key table; ensure that the value is present into a column of a primary key.

What are Keys?

Keys are attribute that helps you to identify a row(tuple) in a relation(table). They allow you to find the relationship between two tables. Keys help you uniquely identify a row in a table by a combination of one or more columns in that table. The database key is also helpful for finding a unique record or row from the table.

What is Primary Key?

A primary key constrain is a column or group of columns that uniquely identifies every row in the table of the relational database management system. It cannot be a duplicate, meaning the same value should not appear more than once in the table.

A table can not have more than one primary key. Primary key can be defined at the column or the table level. If you create a composite primary key, it should be defined at the table level.

What is Foreign Key?

Foreign key is a column that creates a relationship between two tables. The purpose of the Foreign key is to maintain data integrity and allow navigation between two different instances of an entity. It acts as a cross-reference between two tables as it references the primary key of another table. Every relationship in the database should be supported by a foreign key.

Difference between Primary Key and Foreign Key

Here is the important difference between Primary key and Foreign key:

Primary Key Foreign Key

A primary key constrain is a column or group of columns that uniquely identifies every row in the table of the relational database management system. Foreign key is a column that creates a relationship between two tables.

It helps you to uniquely identify a record in the table. It is a field in the table that is a primary key of another table.

Primary Key never accepts null values. A foreign key may accept multiple null values.

The primary key is a clustered index, and data in the DBMS table are physically organized in the sequence of the clustered index. A foreign key cannot automatically create an index, clustered, or non-clustered.

You can have the single Primary key in a table. You can have multiple foreign keys in a table.

The value of the primary key can’t be removed from the parent table. The value of foreign key value can be removed from the child table.

You can define the primary key implicitly on the temporary tables. You cannot define foreign keys on the local or global temporary tables.

Primary key is a clustered index. By default, it is not a clustered index.

No two rows can have any identical values for a primary key. A foreign key can contain duplicate values.

There is no limitation in inserting the values into the table column. While inserting any value in the foreign key table, ensure that the value is present into a column of a primary key.

What is Database Relationship?

The database relationship is associations between one or more tables that are created using join statements. It is used to efficiently retrieve data from the database. There are primarily three types of relationships 1) One-to-One, 2) One-to-many, 3) Many-to-many.

Why use Primary Key?

Here are the cons/benefits of using primary key:

The main aim of the primary key is to identify each and every record in the database table.

You can use a primary key when you do not allow someone to enter null values.

If you delete or update records, the action you specified will be undertaken to make sure data integrity.

Perform restrict operation to rejects delete or update operation for the parent table.

Data are organized in a sequence of clustered index whenever you physically organize DBMS table.

Why use Foreign Key?

Here are the important reasons of using foreign key:

Foreign keys help you to migrate entities using a primary key from the parent table.

A foreign key enables you to link two or more tables together.

It makes your database data consistent.

A foreign key can be used to match a column or combination of columns with primary key in a parent table.

SQL foreign key constraint is used to make sure the referential integrity of the data parent to match values in the child table.

Example of Primary Key


Below is the syntax of Primary Key:

( Column1 datatype, Column2 datatype, PRIMARY KEY (Column-Name) . );


Table_Name is the name of the table you have to create.

Column_Name is the name of the column having the primary key.


StudID Roll No First Name Last Name Email

1 11 Tom Price

2 12 Nick Wright

3 13 Dana Natan

In the above example, we have created a student table with columns like StudID, Roll No, First Name, Last Name, and Email. StudID is chosen as a primary key because it can uniquely identify other rows in the table.

Example of Foreign Key


Below is the syntax of Foreign Key:

column1 datatype, column2 datatype, constraint (name of constraint) FOREIGN KEY [column1, column2…] REFERENCES [primary key table name] (List of primary key table column) …);

The parameter Table Name indicates the name of the table that you are going to create.

The parameters column1, column2… depicts the columns that need to be added to the table.

Constraint denotes the name of constraint you are creating.

References indicate a table with the primary key.


DeptCode DeptName

001 Science

002 English

005 Computer

Teacher ID Fname Lname

B002 David Warner

B017 Sara Joseph

B009 Mike Brunton

In the above example, we have two tables, a teacher and a department in a school. However, there is no way to see which search works in which department.

In this table, adding the foreign key in Deptcode to the Teacher name, we can create a relationship between the two tables.

Teacher ID DeptCode Fname Lname

B002 002 David Warner

B017 002 Sara Joseph

B009 001 Mike Brunton

This concept is also known as Referential Integrity.

Usb Wifi Adapter Not Working

USB WiFi Adapter Not Working [FIXED]







adapters are extremely handy, they won’t keep connection failures at bay.

Below, we explore the necessary steps to restore a Wi-Fi connection when using such a device.

Find more solutions to Wi-Fi connection errors on your PC or laptop in the Windows 10 Hub.

A whole collection of similarly useful guides is available in the Troubleshooting section.



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Download Fortect and install it on your PC.

Start the tool’s scanning process to look for corrupt files that are the source of your problem

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A USB Wi-Fi adapter is a handy little gadget that should be part of your home essentials alongside a good computer or a fast Internet connection.

If your computer has no Wi-Fi connection built into it, you can choose to use a USB Wi-Fi adapter to ensure you get online and continue browsing, streaming Netflix, or even playing games.

USB Wi-Fi adapters eliminate the need for running cables or installing internal hardware, plus you can use them on multiple devices.

If you’re trying to get online but your USB WiFi adapter is not working, here are some solutions you can use.

How can I fix USB WiFi adapter not working? 1. Roll back the network adapter driver

If the button is unavailable, that means there’s no driver to roll back to.

If Windows can’t find a new driver for your network adapter, visit your computer manufacturer’s website to download the latest network adapter driver.

1.1 Update drivers automatically

We strongly suggest you do this process automatically by using the Outbyte Driver Updater tool.

Dedicated software like this one ensures that you download just the right driver for your PC; besides, it also makes the very best recommendations in this sense, so you won’t have to waste time searching the Internet.

Hence, if you strongly need to update your network driver correctly and without any difficulties, proceed confidently with specialized software like Outbyte Driver Updater

2. Check your Wi-Fi connection 3. Turn off Airplane Mode

Make sure the Wi-Fi is on. Then, open Network & Internet settings, as shown above.

Select Airplane mode

Turn it OFF if it is turned on

4. Restart your Wi-Fi router

If the previous solutions didn’t work and your USB WiFi adapter is not working, and you have tried to move closer to your router or access point, you can also restart your Wi-Fi router.

This helps create a new connection to your ISP, but it will disconnect everyone on your network temporarily. It should be one of the last solutions to try though. Here’s what to do:

Unplug the power cable for the router from the power outlet and wait at least 30 seconds

Plug back the router to the power source.

Wait a few minutes for the router to power on fully (you can check this by looking at the status lights on the two devices).

Try and connect your PC again.

5. Run the network troubleshooter 6. Temporarily turn off the firewall

There are times when your firewall or antivirus and anti-malware software may prevent you from connecting to the Internet.

You can temporarily turn it off and try to connect again. Check the software’s documentation for steps on how to do this, although the steps should be quite intuitive.

Expert tip:

7. Uninstall the network adapter driver and restart

Windows will automatically install the latest driver. If Windows doesn’t automatically install a driver, try to install the backup driver you saved before uninstalling.

Alternatively, you can use the method recommended in the first step to use dedicated software for this.

You can apply this solution if your network connection stopped working after a recent update, as well.

8. Use network reset to reinstall network devices

This should be the last step you try if the other solutions don’t help when your USB Wi-Fi adapter is not connecting to the Internet.

It can also help solve connection problems you might have after upgrading from a previous version of Windows to Windows 10, as well as fix problems where you can connect to the Internet but not to shared network drives.

It removes any network adapters you have installed and the settings for them.

Once your computer restarts, network adapters are reinstalled, with default settings.

Note: To use network reset, you must run Windows 10 version 1607 or later.

After using network reset, you may need to reinstall and set up other networking software you might be using, such as VPN client software or virtual switches from Hyper‑V.

Note: Network reset might set each one of your known network connections to a public network profile where your computer is not discoverable to other PCs and devices on the network, which can help make your PC more secure.

If your PC is part of a homegroup or used for file or printer sharing, you need to make it discoverable again by setting it to use a private network profile.

Here’s how to make your computer discoverable again:

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Network Security – Application Layer

Network Security – Application Layer

Various business services are now offered online though client-server applications. The most popular forms are web application and e-mail. In both applications, the client communicates to the designated server and obtains services.

While using a service from any server application, the client and server exchange a lot of information on the underlying intranet or Internet. We are aware of fact that these information transactions are vulnerable to various attacks.

Network security entails securing data against attacks while it is in transit on a network. To achieve this goal, many real-time security protocols have been designed. Such protocol needs to provide at least the following primary objectives −

The parties can negotiate interactively to authenticate each other.

Establish a secret session key before exchanging information on network.

Exchange the information in encrypted form.

Interestingly, these protocols work at different layers of networking model. For example, S/MIME protocol works at Application layer, SSL protocol is developed to work at transport layer, and IPsec protocol works at Network layer.

In this chapter, we will discuss different processes for achieving security for e-mail communication and associated security protocols. The method for securing DNS is covered subsequently. In the later chapters, the protocols to achieve web security will be described.

E-mail Security

Nowadays, e-mail has become very widely used network application. Let’s briefly discuss the e-mail infrastructure before proceeding to know about e-mail security protocols.

E-mail Infrastructure

The simplest way of sending an e-mail would be sending a message directly from the sender’s machine to the recipient’s machine. In this case, it is essential for both the machines to be running on the network simultaneously. However, this setup is impractical as users may occasionally connect their machines to the network.

In general, the e-mail infrastructure consists of a mesh of mail servers, also termed as Message Transfer Agents (MTAs) and client machines running an e-mail program comprising of User Agent (UA) and local MTA.

Typically, an e-mail message gets forwarded from its UA, goes through the mesh of MTAs and finally reaches the UA on the recipient’s machine.

The protocols used for e-mail are as follows −

Simple mail Transfer Protocol (SMTP) used for forwarding e-mail messages.

Post Office Protocol (POP) and Internet Message Access Protocol (IMAP) are used to retrieve the messages by recipient from the server.


Basic Internet e-mail standard was written in 1982 and it describes the format of e-mail message exchanged on the Internet. It mainly supports e-mail message written as text in basic Roman alphabet.

By 1992, the need was felt to improve the same. Hence, an additional standard Multipurpose Internet Mail Extensions (MIME) was defined. It is a set of extensions to the basic Internet E-mail standard. MIME provides an ability to send e-mail using characters other than those of the basic Roman alphabet such as Cyrillic alphabet (used in Russian), the Greek alphabet, or even the ideographic characters of Chinese.

Another need fulfilled by MIME is to send non-text contents, such as images or video clips. Due to this features, the MIME standard became widely adopted with SMTP for e-mail communication.

E-Mail Security Services

Growing use of e-mail communication for important and crucial transactions demands provision of certain fundamental security services as the following −

Confidentiality − E-mail message should not be read by anyone but the intended recipient.

Authentication − E-mail recipient can be sure of the identity of the sender.

Integrity − Assurance to the recipient that the e-mail message has not been altered since it was transmitted by the sender.

Non-repudiation − E-mail recipient is able to prove to a third party that the sender really did send the message.

Proof of submission − E-mail sender gets the confirmation that the message is handed to the mail delivery system.

Proof of delivery − Sender gets a confirmation that the recipient received the message.

Security services such as privacy, authentication, message integrity, and non-repudiation are usually provided by using public key cryptography.

Typically, there are three different scenarios of e-mail communication. We will discuss the methods of achieving above security services in these scenarios.

One-to-One E-mail

In this scenario, the sender sends an e-mail message to only one recipient. Usually, not more than two MTA are involved in the communication.

Let’s assume a sender wants to send a confidential e-mail to a recipient. The provision of privacy in this case is achieved as follows −

The sender and receiver have their private-public keys as (SPVT, SPUB) and (RPVT, RPUB) respectively.

The sender generates a secret symmetric key, KS for encryption. Though the sender could have used RPUB for encryption, a symmetric key is used to achieve faster encryption and decryption.

The sender encrypts message with key KS and also encrypts KS with public key of the recipient, RPUB.

The sender sends encrypted message and encrypted KS to the recipient.

The recipient first obtains KS by decrypting encoded KS using his private key, RPVT.

The recipient then decrypts message using the symmetric key, KS.

If message integrity, authentication, and non-repudiation services are also needed in this scenario, the following steps are added to the above process.

The sender produces hash of message and digitally signs this hash with his private key, SPVT.

The sender sends this signed hash to the recipient along with other components.

The recipient uses public key SPUB and extracts the hash received under the sender’s signature.

The recipient then hashes the decrypted message and now compares the two hash values. If they match, message integrity is considered to be achieved.

Also, the recipient is sure that the message is sent by the sender (authentication). And lastly, the sender cannot deny that he did not send the message (non-repudiation).

One-to-Multiple Recipients E-mail

In this scenario, the sender sends an e-mail message to two or more recipients. The list is managed by the sender’s e-mail program (UA + local MTA). All recipients get the same message.

Let’s assume, the sender wants to send confidential e-mail to many recipients (say R1, R2, and R3). The provision of privacy in this case is achieved as follows −

The sender and all recipients have their own pair of private-public keys.

The sender generates a secret symmetric key, Ks and encrypts the message with this key.

The sender then encrypts KS multiple times with public keys of R1, R2, and R3, getting R1PUB(KS), R2PUB(KS), and R3PUB(KS).

The sender sends encrypted message and corresponding encrypted KS to the recipient. For example, recipient 1 (R1) receives encrypted message and R1PUB(KS).

Each recipient first extracts key KS by decrypting encoded KS using his private key.

Each recipient then decrypts the message using the symmetric key, KS.

For providing the message integrity, authentication, and non-repudiation, the steps to be followed are similar to the steps mentioned above in one-to-one e-mail scenario.

One-to-Distribution List E-mail

In this scenario, the sender sends an e-mail message to two or more recipients but the list of recipients is not managed locally by the sender. Generally, the e-mail server (MTA) maintains the mailing list.

The sender sends a mail to the MTA managing the mailing list and then the mail is exploded by MTA to all recipients in the list.

In this case, when the sender wants to send a confidential e-mail to the recipients of the mailing list (say R1, R2, and R3); the privacy is ensured as follows −

The sender and all recipients have their own pair of private-public keys. The Exploder Server has a pair of private-public key for each mailing list (ListPUB, ListPVT) maintained by it.

The sender generates a secret symmetric key Ks and then encrypts the message with this key.

The sender then encrypts KS with the public key associated with the list, obtains ListPUB(KS).

The sender sends encrypted message and ListPUB(KS). The exploder MTA decrypts ListPUB(KS) using ListPVT and obtains KS.

The exploder encrypts KS with as many public keys as there are members in the list.

The Exploder forwards the received encrypted message and corresponding encrypted KS to all recipients in the list. For example, the Exploder forwards the encrypted message and R1PUB(KS) to recipient 1 and so on.

For providing the message integrity, authentication, and non-repudiation the steps to be followed are similar as given in case of one-to-one e-mail scenario.

Interestingly, the e-mail program employing above security method for securing e-mail is expected to work for all the possible scenarios discussed above. Most of the above security mechanisms for e-mail are provided by two popular schemes, Pretty Good Privacy (PGP) and S/MIME. We discuss both in the following sections.


Pretty Good Privacy (PGP) is an e-mail encryption scheme. It has become the de-facto standard for providing security services for e-mail communication.

As discussed above, it uses public key cryptography, symmetric key cryptography, hash function, and digital signature. It provides −


Sender Authentication

Message Integrity


Along with these security services, it also provides data compression and key management support. PGP uses existing cryptographic algorithms such as RSA, IDEA, MD5, etc., rather than inventing the new ones.

Working of PGP

Hash of the message is calculated. (MD5 algorithm)

Resultant 128 bit hash is signed using the private key of the sender (RSA Algorithm).

The digital signature is concatenated to message, and the result is compressed.

A 128-bit symmetric key, KS is generated and used to encrypt the compressed message with IDEA.

KS is encrypted using the public key of the recipient using RSA algorithm and the result is appended to the encrypted message.

The format of PGP message is shown in the following diagram. The IDs indicate which key is used to encrypt KS and which key is to be used to verify the signature on the hash.

In PGP scheme, a message in signed and encrypted, and then MIME is encoded before transmission.

PGP Certificate

PGP key certificate is normally established through a chain of trust. For example, A’s public key is signed by B using his public key and B’s public key is signed by C using his public key. As this process goes on, it establishes a web of trust.

In a PGP environment, any user can act as a certifying authority. Any PGP user can certify another PGP user’s public key. However, such a certificate is only valid to another user if the user recognizes the certifier as a trusted introducer.

Several issues exist with such a certification method. It may be difficult to find a chain leading from a known and trusted public key to desired key. Also, there might be multiple chains which can lead to different keys for desired user.

PGP can also use the PKI infrastructure with certification authority and public keys can be certified by CA (X.509 certificate).


S/MIME stands for Secure Multipurpose Internet Mail Extension. S/MIME is a secure e-mail standard. It is based on an earlier non-secure e-mailing standard called MIME.

Working of S/MIME

S/MIME approach is similar to PGP. It also uses public key cryptography, symmetric key cryptography, hash functions, and digital signatures. It provides similar security services as PGP for e-mail communication.

The most common symmetric ciphers used in S/MIME are RC2 and TripleDES. The usual public key method is RSA, and the hashing algorithm is SHA-1 or MD5.

S/MIME specifies the additional MIME type, such as “application/pkcs7-mime”, for data enveloping after encrypting. The whole MIME entity is encrypted and packed into an object. S/MIME has standardized cryptographic message formats (different from PGP). In fact, MIME is extended with some keywords to identify the encrypted and/or signed parts in the message.

S/MIME relies on X.509 certificates for public key distribution. It needs top-down hierarchical PKI for certification support.

Employability of S/MIME

In practice, although most e-mailing applications implement S/MIME, the certificate enrollment process is complex. Instead PGP support usually requires adding a plug-in and that plug-in comes with all that is needed to manage keys. The Web of Trust is not really used. People exchange their public keys over another medium. Once obtained, they keep a copy of public keys of those with whom e-mails are usually exchanged.

Implementation layer in network architecture for PGP and S/MIME schemes is shown in the following image. Both these schemes provide application level security of for e-mail communication.

One of the schemes, either PGP or S/MIME, is used depending on the environment. A secure e-email communication in a captive network can be provided by adapting to PGP. For e-mail security over Internet, where mails are exchanged with new unknown users very often, S/MIME is considered as a good option.

DNS Security

In the first chapter, we have mentioned that an attacker can use DNS Cache Poisoning to carry out an attack on the target user. Domain Name System Security Extensions (DNSSEC) is an Internet standard that can foil such attacks.

Vulnerability of Standard DNS

In a standard DNS scheme, whenever the user wants to connect to any domain name, his computer contacts the DNS server and looks up the associated IP address for that domain name. Once IP address is obtained, the computer then connects to that IP address.

In this scheme, there is no verification process involved at all. A computer asks its DNS server for the address associated with a website, the DNS server responds with an IP address, and your computer undoubtedly accepts it as legitimate response and connects to that website.

DNSSEC Defined

DNS lookup, when performed using DNSSEC, involves signing of replies by the responding entity. DNSSEC is based on public-key cryptography.

In DNSSEC standard, every DNS zone has a public/private key pair. All information sent by a DNS server is signed with the originating zone’s private key for ensuring authenticity. DNS clients need to know the zone’s public keys to check the signatures. Clients may be preconfigured with the public keys of all the top-level domains, or root DNS.

With DNSSEC, the lookup process goes as follows −

Computer checks the root zone’s signing key and confirms that it is the legitimate root zone with true information.

Domain Name Time to live Type Value

86400 NS

86400 A 36..1.2.3

86400 KEY 3682793A7B73F731029CE2737D…

86400 SIG 86947503A8B848F5272E53930C…

Thus, it is considered that when DNSSEC is fully rolled out, the user’s computer is able to confirm that DNS responses are legitimate and true, and avoid DNS attacks launched through DNS cache poisoning.


The process of securing e-mails ensures the end-to-end security of the communication. It provides security services of confidentiality, sender authentication, message integrity, and non-repudiation.

Two schemes have been developed for e-mail security: PGP and S/MIME. Both these schemes use secret-key and public-key cryptography.

Standard DNS lookup is vulnerable to the attacks such as DNS spoofing/cache poisoning. Securing DNS lookup is feasible through the use of DNSSEC which employs the public-key cryptography.

In this chapter, we discussed the mechanisms used at application layer to provide network security for end-to-end communication.


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