Symmetric and asymmetric encryption are two methods to safeguard data in motion. Without these encryption methods, data is sent in plaintext for anyone with prying eyes to view.
When discussing symmetric vs asymmetric encryption, we’re talking about two ways to convert messages into secret code that can only be decoded with a specific key. While both methods share the same goal, they have unique ways of protecting data.
In this article, we’ll decrypt the secretive process of asymmetric and symmetric encryption, understand how they’re different, look at some of their use cases, and discuss the advantages and disadvantages of each one.
Are you ready? Let’s start.
What Is Encryption?
Encryption turns plaintext data into an unreadable code (or ciphertext) that can only be understood if decrypted. There are various types of encryption algorithms used to encrypt data. As we’ll see later on, some are far safer than others.
Here’s an example of an encrypted message:
Plaintext: This is an encrypted message.
Ciphertext: meczoiCzW3ddp8styLxebEipfjyNA0oX2Z6ejoJrCn07XdBhYa0m7caV5tcV3/X4
Encryption isn’t a new way of keeping data safe. It’s been around for thousands of years.
In 600 BC, Spartan warriors used a scytale cipher to disguise messages. The cipher was a leather strap that wrapped around a wooden rod. If the message written on the leather is read, it appears nonsensical. To decrypt it, the reader must have the correct rod.
Julius Caesar popularized a cipher that shifts characters three places to the right. So, an A becomes a D, and a B becomes an E. This is a simple cipher, but it could still prove effective if you’re unaware of how to decrypt it.
Here’s an example of a message that’s been encrypted with the Caesar cipher.
Plaintext: Example of the Caesar cipher.
Ciphertext: Hadpsoh ri wkh Fdhvdu flskhu.
Fast forward a couple of thousand years, and we see that encryption played a big role during WWII. Cryptographer Alan Turing, in particular, played a massive role in decrypting secret Nazi messages.
It wasn’t until the 1970s that encryption went digital. IBM created DES, the first digital cipher, to encrypt customer data. In 1973, the US made it the national standard.
In 2000, Advanced Encryption Standard (AES) replaced DES as the national standard. We also see the rise of asymmetric encryption algorithms such as RSA, ECC, and Diffie-Hellman.
Today, the vast majority of data on the Internet is encrypted.
What Is Symmetric Encryption?
Data can be made unreadable in two ways. One method is symmetric encryption.
When we use symmetric key encryption to encode data, we use a single key that encrypts and decrypts data. Prior to sending data, a symmetric algorithmic key is used to scramble it. It’s then sent in the form of ciphertext to its recipient, who uses an identical key to decrypt that data so they can read it.
Symmetric encryption is commonly referred to as private key cryptography for this reason.
Common Symmetric Encryption Algorithms
Symmetric encryption doesn't use a single algorithm to encrypt data. Rather, it's an umbrella term for various types of algorithms. Here are a few of the most popular symmetric key algorithms.
Advanced Encryption Standard (AES)
Perhaps the most popular and safest encryption algorithm is AES. Data is encrypted in 128-bit blocks, which are then encrypted using 128, 192, and 256-bit keys. The longer the key length is, the stronger the encryption. AES is considered one of the safest encryption algorithms because it encrypts in layers, uses a variety of key lengths, and is resistant to brute-force attacks.
Data Encryption Standard (DES)
Created in the early 1970s, DES was one of the first encryption algorithms created. It takes 64-bit blocks and converts them into ciphertext using 56-bit keys. While DES is still in use today by way of Triple DES, NIST considers it a legacy encryption algorithm and advises users to switch to AES.
3DES
3DES, also known as Triple DES, evolved from DES. It was developed in 1998 and differs from DES because it has a key length that is three times longer. After researchers compromised the key, NIST deprecated 3DES for new technology, meaning its use was allowed but discouraged. As of the end of 2023, NIST has disallowed the use of 3DES for encryption except for specific purposes.
Rivest Cipher 4 (RC4)
RC4 is a quick and simple cipher that is also very flawed. It was used as the TLS encryption algorithm from 1999 to 2015, but after a series of exploits, it was retired. Unlike block ciphers, which encrypt a certain block of bits at a time, RC4 functions as a stream cipher, encrypting each digit one at a time.
Advantages and Disadvantages of Symmetric Encryption
The chief advantage of symmetric encryption is how fast it can encrypt large amounts of data. Symmetric encryption uses a single key, shorter key lengths, and requires less computational power than asymmetric encryption. It’s also a simpler encryption process as it requires only one key.
However, the simplicity of a single key is a double-edged sword. One key means that should this key be discovered, cybercriminals could decrypt sensitive data.
Another downside of using one key is that it’s not a very scalable way to encrypt the data of many users. Scaling this process involves creating unique keys for every user. This taxes the key management process.
When Is Symmetric Encryption Used?
There are many use cases for symmetric encryption, including:
- WiFi: WPA2 uses symmetric encryption to secure communication between a device and a router.
- Disk encryption: Encrypts all data, including temporary files and swap space.
- Data encryption: Transparent Data Encryption (TDE) in SQL servers uses AES to protect data at rest
What Is Asymmetric Encryption?
The other encryption algorithm is asymmetric encryption.
As opposed to symmetric encryption, asymmetric encryption—also known as public key encryption—uses multiple keys. To make this connection possible, a public and a private key are used to encrypt, decrypt, and keep data safe and secure.
Similar to symmetric encryption, asymmetric encryption uses an algorithm known as a cipher to turn plaintext into ciphertext to encrypt data. The recipient then uses a key to decrypt the ciphertext so that it can be read.
Let’s say you want to send a message to your friend Sarah using asymmetric encryption.
First, Sarah will send you her public key. This key is available to anyone who wants to exchange information with Sarah safely. You write your message in plaintext and then encrypt it with Sarah’s public key. This encrypted message is then sent to Sarah, who decrypts it with her private key, which only she has access to.
In this case, anyone can use the public key to encrypt a message, but only those with the private key can decrypt it and read the message’s contents.
Further Clarity
Think of it as a safe with a lock and two keys. When one key locks the safe, only the other key can open it; you cannot unlock the safe with the same key that locked it.
If you encrypt data (for example, a credit card number) using the public key, it can only be read by the private key holder (i.e., an online payment gateway).
It doesn't matter if a third party intercepts the transmission; the public key is useless in breaking the encryption.
Common Asymmetric Encryption Algorithms
Not all asymmetric encryption algorithms are created equal. Some are far more secure than others. Here are the most popular ones.
Rivest-Shamir-Adleman (RSA)
Invented in 1977, RSA is the most commonly used form of public key encryption. Despite being created decades ago, it remains the gold standard due to its complexity in creating public-private key pairs.
Elliptic Curve Cryptography (ECC)
ECC uses an elliptic curve to develop public and private key pairs. It isn’t as safe as RSA but is faster due to its smaller key size.
Digital Signature Algorithm (DSA)
DSA is a simple signature algorithm. This means there’s no key exchange; rather, RSA is used for signature generation and verification. To create a unique signature, DSA uses data and a private key to create a signature. This signature is then used to authenticate and verify documents and data to ensure they have not been tampered with.
Advantages and Disadvantages of Asymmetric Encryption:
Its biggest advantage over symmetric encryption is its security. Remember that asymmetric encryption uses multiple keys.
This means that should one key be compromised, your data may still remain safe. This isn’t the case with symmetric encryption, where if a cybercriminal has your key they’re guaranteed to be able to decrypt your data.
The biggest drawback of asymmetric keys is the speed. Generating multiple keys takes time, which slows down the encryption process. This makes it a less-than-optimal choice if you want to encrypt servers, hard drives, and databases.
When Is Asymmetric Encryption Used?
When it comes to symmetric vs asymmetric encryption, the latter is more secure but that doesn’t mean it should be used for all encryption tasks.
Here are some of the most common ways asymmetric encryption is used:
- SSL/TLS: Encrypted HTTPS communication relies in part on asymmetric key pairs.
- Email encryption: Most email providers use TLS to encrypt messages and thus rely on public key encryption methods.
- Digital signatures: DSA encryption powers digital signatures, which are used to authenticate and verify data.
Symmetric vs Asymmetric Encryption
Before we get into the differences between these encryption types, let’s discuss how they work together.
These encryption methods work together when using public key infrastructure (PKI). PKI starts by using asymmetric encryption to securely deliver session keys, otherwise known as symmetric keys.
As we now know, symmetric keys are faster than asymmetric keys and ideally are used if your aim is speedy data transfer. However, we must first use an asymmetric key pair to send these symmetric keys.
After exchanging session keys, there’s no more reason to use asymmetric keys.
Key Differences
While both encrypt data, there are some key differences to remember.
Which type of algorithm you use depends on your needs.
If speed is the most important factor for you, we recommend using symmetric encryption. It’s faster and more efficient than asymmetric encryption and can safely transfer a high volume of data. For this reason, symmetric encryption algorithms are often used to store data on a device.
If you value security, you may opt for asymmetric encryption. It’s generally considered the more secure of the two algorithm methods, as it uses two separate keys to encrypt and decrypt.
For this reason, asymmetric encryption is the preferred choice when securely exchanging keys. It ensures that messages are confidential, authenticated, and non-repudiated (proof that they have not been tampered with).
Conclusion: Asymmetric vs Symmetric Encryption
Both symmetric and asymmetric encryption algorithms are used to securely send data over the internet. While they both have the same goal, how they secure data differs.
Symmetric algorithms are fast but less secure than asymmetric algorithms. Despite their differences, they can work in tandem, such as when PKI is used. The exchange begins by connecting using public keys and then securely sending a session key.
Which key you use, symmetric or asymmetric, depends on what you prefer most when sending data, such as speed or security.
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