Symmetric encryption is a means of protecting data using a secret key to encrypt (lock) and decrypt (unlock) it. The sender and recipient share the key or password to gain access to the information. The key can be a word; a phrase; or a nonsensical or random string of letters, numbers, and symbols.
Many organizations use symmetric encryption because it is relatively inexpensive. But it does come with some flaws. A key in symmetric encryption can be used forever. And that sometimes leads organizations to forget to change them. As a result, even users who may no longer be part of the company can intercept and read encrypted data.
Think of symmetric encryption as the combination to an office vault. Anyone who has it can unlock and access the vault’s contents.
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What Are the Common Symmetric Encryption Algorithms?
Symmetric encryption uses algorithms to convert data into a form that can only be understood by those who have access to the secret key. The key can be a code or random string of letters, numbers, and symbols generated by a random number generator (RNG). Some of the symmetric algorithms available are:
1. Data Encryption Standard
Data Encryption Standard (DES) used to be the standardized method for encrypting various modes of electronic communications but was soon phased out. It was found weak and insufficient to address the higher processing power requirements of most modern computers. Three-key DES (3DES), in particular, does not meet the National Institute of Standards and Technology (NIST) and Payment Card Industry Data Security Standard (PCI-DSS) requirements. Note, however, that most Europay, Mastercard, and Visa (EMV) chip-based cards still use 3DES.
2. Advanced Encryption Standard
One of the most popular symmetric encryption algorithms still in use to date is the Advanced Encryption Standard (AES). The NIST set this algorithm as the standard for encrypting electronic data. The AES cipher contains a block size of 128 bits but may include different key lengths (AES-128, AES-192, and AES-256).
3. International Data Encryption Algorithm
The International Data Encryption Algorithm (IDEA) is widely used to secure big data separated into chunks.
Other symmetric encryption algorithms include Blowfish, Rivest Cipher 4 (RC4), Rivest Cipher 5 (RC5), and Rivest Cipher 6 (RC6).
How Does Symmetric Encryption Work?
Symmetric encryption works the same way as locking the door to a family’s home to which only the husband and the wife hold the key. Even when neighbors or their in-laws try to open the door, they can’t do so unless they use any of the couple’s keys. When other people take the key from the husband or wife, they can open the door even without the knowledge or presence of the couple.
In symmetric encryption, the key that encrypts a message or file is the same key that can decrypt them. The sender of the data uses the symmetric key algorithm to encrypt the original data and turn it into cipher text. The encrypted message is then sent to the receiver who uses the same symmetric key to decrypt or open the cipher text or turn it back into readable form.
If somebody other than the intended recipient gets access to the symmetric key, he/she can also decrypt the message. For this reason, symmetric encryption is considered less secure compared to asymmetric encryption. Needless to say, careful and secure handling of the key is necessary to protect data and its owners.
What Is Symmetric Encryption Used for?
Despite being an older form of securing data, symmetric encryption is still widely used because it is easy to deploy compared to asymmetric encryption (i.e., using a pair of related keys to encrypt and decrypt data). With better performance, symmetric cryptography is used for securing tons of data, such as that contained in databases.
Symmetric encryption also plays an important role in website security, specifically on how Hypertext Transfer Protocol Secure (HTTPS) works. While asymmetric encryption is used at the initial stage of an HTTPS connection, the rest of the data transfer is handled using symmetric encryption, as it is faster.
Several messaging applications use symmetrical encryption, particularly the AES algorithm. Some examples are Telegram, Line, and KakaoTalk. Aside from securing web browsing and messaging applications, other use cases of symmetrical encryption are:
- Managing cloud storage security
- Preventing fraud in payment applications and card transactions
- Validating the identity of a message sender
- Generating random numbers or hashing
What Are the Drawbacks of Symmetric Encryption?
While this cryptographic method has advantages, it does have some flaws that include:
1. Prone to Key Leakage
Symmetric encryption is easy to hack because once a portion of the key is leaked, hackers can easily reconstruct the entire key and gain access to confidential data.
2. Lack of Attribution Data
Another downside of using symmetric encryption is its lack of embedded metadata or attribution data. It does not allow users to record information in an access control list nor let them monitor usage based on expiration dates.
3. Absence of Management System
Key management is essential when using symmetric encryption. When the keys in use remain few, manual monitoring is possible. However, when used on a large scale, manually tracking secret keys can be impractical, which can become problematic, particularly for transactions that contain tons of sensitive information, such as millions of EMV card payments.
Symmetric encryption is an ideal method of securing sensitive and vital data, but it also comes with a few challenges that need to be addressed. That is particularly true for financial and banking institutions where security and audibility are critical.