14.5.1. Symmetric Encryption

• Uses a single key for encryption and decryption.

Symmetric encryption is a type of encryption where the same key is used both to encrypt and decrypt data. This means that if you lock up your data with a key, you must use that exact same key to unlock and read the data again. One of the key characteristics of symmetric encryption is its relative efficiency in terms of speed compared to asymmetric encryption, making it suitable for encrypting large amounts of data.

Think of symmetric encryption like a locked box that uses a single key. You can put your valuable documents inside and lock the box. To access those documents again, you need the same key that locked the box. If you lose that key, you won’t be able to open the box and see your documents.

• Algorithms: AES, DES

There are several algorithms used for symmetric encryption, of which AES (Advanced Encryption Standard) and DES (Data Encryption Standard) are the most frequently discussed. AES is presently the more secure option and is widely adopted due to its robust security features and faster processing speeds. DES, while once a standard, is now considered outdated and is generally not recommended due to vulnerabilities.

If you think of strongbox encryption as choosing a locking mechanism for your valuables, AES would represent a modern, highly secure key mechanism that provides solid protection, while DES would be akin to an old-fashioned lock that is easily picked and should be avoided in favor of newer, tougher security measures.

Example: AES

Cipher cipher = Cipher.getInstance("AES");
cipher.init(Cipher.ENCRYPT_MODE, secretKey);
byte[] encrypted = cipher.doFinal(plainText.getBytes());

In this example, we use the AES algorithm to encrypt some plain text. First, we acquire a Cipher instance configured for AES. Then, we initialize this cipher using a secret key to set it in encryption mode. Finally, we call the doFinal method, passing the plain text, which returns the encrypted byte array. This byte array represents the secured version of your original text.

Think of this code as the process of using your key to lock your box. First, you need to have the box (the Cipher object), then you insert the key (the secret key) and lock it with the contents inside (the plain text). When you do this, you cannot see what’s inside anymore - it’s securely locked away!

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