“There is some good in this world, and it’s worth fighting for.” ― J.R.R. Tolkien, The Two Towers
Contents
- Conclusion
Alternatives to Java for Windows, Linux, Mac, BSD, Web and more. Filter by license to discover only free or Open Source alternatives. This list contains a total of 25+ apps similar to Java. How to: Fix Java Command-Line Tool Pop-Up on Mac OS Truong Nguyen August 29, 2017 How-To After upgrading to a newer version of Mac OS X (Yosemite 10.10 and El Capitan 10.11) or macOS (Sierra 10.12 and High Sierra 10.13), you may end up getting an annoying new pop-up message whenever you start your computer.
1. Introduction
A Message Authentication Code or a MAC provides a way to guarantee that a message (a byte array) has not been modified in transit. It is similar to a message digest to calculate a hash, but uses a secret key so that only a person with the secret key can verify the authenticity of the message.
Using a MAC to ensure safe transmission of messages requires that the two parties share a secret key to be able to generate and verify the MAC. There are two approaches available here – the two parties can share a secret key directly. Or the secret key can be generated using a password. We investigate both approaches below.
2. Java Imports
The following java imports are required.
3. Generating a Key
Let us now look into generating a secret key that the parties exchanging messages can share. Either party can generate the key as shown here and send it to the other party via a secure channel.
The following KeyGenerator algorithms are supported in my version of java. Of these, ones starting with HMAC are useful as a secret key for a MAC.
4. Saving and Restoring a Key
You will need to send the key to the receiver to enable verification. So you need to be able to save and restore the key. Here is how you can save it to a file.
And restoring the key is also quite simple.
5. Generating the Message Authentication Code (MAC)
Once you generate the key, you can proceed with generating the MAC for a message.
Use one of the following values for the algorithm (algo):
The static method processFile() is defined as follows:
Once the MAC is obtained, you can send it to the other party along with the file for verification.
6. Using a Password for Key Generation
While one way of generating a secret key is to directly use a KeyGenerator as shown above, sometimes it is more convenient to use a password to generate the key. This can be accomplished using a SecretKeyFactory.
One aspect of using a password for key generation is that it requires the use of a salt. This salt can be generated using the SecureRandom class while generating the key, but the same salt must be used again for verification. This means the salt also must be communicated to the message receiver, but it need not be kept secret – it can be transmitted as plain-text.
The following code generates and prints the salt for transmission.
And now for the generation of the secret key.
Use one of the following values for the algorithm (algo):
Once you have the SecretKey, the procedure for computing the MAC is the same as above. However, you will need to use one of the following algorithms:
Conclusion
In this article, we learned how to compute a MAC (Message Authentication Code) for a message. A MAC requires a secret key which needs to be shared among the parties in the exchange. A password can be used for generating the secret key too.
Last updated: January 16, 2019
Update: Please see our Java Support in Safari 12 article for the latest information on Java support in Safari on macOS. The option to allow plug-ins described below is no longer supported by Safari.
No matter which web browser you use on your computer, you will need the Java plug-in from Oracle in order to view content that uses Java, such as Java applets. The Safari web browser on Mac from Apple is no exception. Java applets are common on the Internet. It is important, therefore, to know how to enable and disable Java in Safari on Mac if it is your web browser of choice.
First, please be certain the version of Java on your computer is current. Once you have verified Java is installed on your computer, please follow the instructions below to learn how to enable or disable Java in Safari on Mac.
What Is Java Used For On Macbook Air
1. Launch the Safari application, and click the Safari file menu. Select Preferences from the drop-down menu.
What Is Java Used For On A Mac
2. The Preferences dialog will launch in a new window. Click the Security icon.
To enable Internet plug-ins, including Java, to load in Safari, check the Internet Plugins: Allow Plug-ins check box. Unlike Safari on Windows, there is no individual check box for Enable Java for Safari on Mac.
3. When you encounter Java content in Safari, Safari will block the content from loading. You will see a notification in the browser window where the Java content would otherwise load:
What Is Java Used For On Mac Computers
4. Click the right-arrow in the notification. A Do you want to trust the website… dialog will display.
In this case, we visited the Java.com web site to load a test Java applet. Since we trust the web site, we clicked the Trust button to allow java.com to use the Java plug-in. When we re-visit the Java content on this web site, the Java content will now display.
5. You can manage your trusted web sites, and choose degrees of trust, by returning to the Security settings of Safari’s Preferences window. Adjacent to the Internet Plugins: Allow Plug-ins check box, click the Website Settings… button.
A new dialog will launch. The dialog displays all of the Internet plug-ins currently installed. To manage the web sites you have trusted to use the Java plug-in, click Java in the left navigation pane. The list of web sites you have already trusted will display.
Update Java On Mac
Use the pull-down menu adjacent to the web site in the list to choose a level of trust you want to extend to this site. You may choose from Ask, Block, Allow or Allow Always (or Run In Unsafe Mode). You may delete a web site from this list by highlighting it with your mouse, and clicking the minus button at the bottom of the list.
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