AES and RSA Encryption: Difference and Similarities

Have you ever wondered how your sensitive data is kept secure during online transactions? Are you curious about the differences and similarities between RSA vs AES encryption? You’re not alone. Over 80% of websites use at least one form of encryption to protect their data.

In this article, we delve into the intriguing world of data protection and uncover the difference between AES and RSA encryption.

By understanding these popular encryption methods, you’ll gain valuable insights into the inner workings of data protection.

Table of Contents

  1. What Is AES?
  2. What Is RSA?
  3. Difference Between AES and RSA Encryption
  4. How Do AES and RSA Work Together?
  5. AES vs RSA Encryption Vulnerabilities
AES-VS-RSA Encryption
Image by storyset on Freepik

What Is AES?

AES, or Advanced Encryption Standard, is a widely used encryption algorithm that ensures secure communication and data protection. It operates on blocks of data, typically 128 bits, and uses only one key (same key) of either 128, 192, or 256 bits to encrypt and decrypt information.

It’s a symmetric algorithm using a block cipher and the same encryption and decryption key. Let’s take a look at how the AES algorithm works.

How Does AES Encryption Work?

Understanding how the AES encryption algorithm works is one way to answer the “What is the difference between the AES and RSA algorithms?” question.

AES encryption is an algorithm based on symmetric encryption. It’s used for encryption and decryption and consists of three key components: the encryption key, the encryption process, and the decryption process.

  1. The encryption key is crucial as both communicating parties share it.
  2. It involves transforming the plaintext into an unreadable format called ciphertext.
  3. The decryption takes the ciphertext and transforms it back into plaintext.

AES is one of the most secure encryptions available. Want to get more technical? Here’s an overview of how the Advanced Encryption Algorithm functions:

First, the AES algorithm expands the secret key to generate a set of round keys. Then, AES replaces each data byte with another from a substitution table known as the S-box. After substitution, AES shuffles the bytes within each data block using permutation.

This mixing operation is known as MixColumns. By combining these steps, the AES symmetric key algorithm ensures that even if attackers gain access to the encrypted data, they won’t be able to decipher it without the corresponding key.

What Is RSA?

RSA, which stands for Rivest Shamir and Adleman, is a widely used public-key asymmetric encryption algorithm. Unlike AES, it operates on the principle of using a pair of keys: public and private. The public key is used to encrypt data, while the private key is used to decrypt it, ensuring secure communication and data protection.

Let’s explore how the RSA asymmetric key algorithm works in more detail.

How Does RSA Encryption Work?

The RSA encryption algorithm relies on the mathematical properties of large prime numbers. The process begins by generating a pair of keys: a public key and a private key. The public key is shared openly, allowing anyone to encrypt messages for the owner of the private key. To decrypt the message, the recipient uses their private key, which is never shared.

The security of the RSA asymmetric algorithm depends on the difficulty of factoring the product of two large prime numbers. The larger the key, the more computationally intensive it becomes for attackers to factor it, making RSA a robust choice for secure communications.

Here’s a simplified explanation of the math behind RSA encryption. Let’s suppose Alice wants to send an encrypted message to her friend Bob.

  1. Alice selects two large prime numbers: p and q.
  2. She multiplies these primes to create a large number, n.
  3. Alice computes φ(n), a number related to her prime choices.
  4. She publicly announces a specific number.
  5. Using mathematical formulas, Alice calculates a private key, which we’ll call d.
  6. To send a message to Bob, Alice converts it into a number using a specific method.
  7. She encrypts the message using the public numbers (n and the chosen public number).
  8. Bob, to read the message, uses the private key created by Alice.

Difference Between AES and RSA Encryption

Let’s explore the difference between AES vs RSA encryption by looking at key type, speed and efficiency of key control, security strength, and use cases.

Key Differences

Two of the most commonly used encryptions, Advanced Encryption Standard and Rivest Shamir and Adleman, differ in the type of key used to encrypt and decrypt data. AES uses symmetric keys, which are the same for encryption and decryption. RSA, on the other hand, uses asymmetric keys (public key and private key), which are different for encryption and decryption.

Speed and Efficiency

You’ll notice that AES is faster than RSA when it comes to encrypting and decrypting data. It’s also more efficient for memory usage, as it doesn’t require the same number of calculations as RSA.

Additionally, AES is more suitable for hardware implementations, as its encryption and decryption processes are faster. On the other hand, RSA is better suited for software implementation, as its more secure encryption and decryption processes require more complex calculations.

Private Key and Public Key Management

You can generate AES randomly in large quantities. In contrast, RSA keys require complex mathematical calculations, and you can only create them in pairs.

When distributing them, AES keys work with symmetrical key algorithms, such as Diffie-Hellman, while RSA requires a secure channel to ensure confidentiality.

The best way to store AES keys is in hardware to software-based key management systems. RSA keys, particularly private keys (any user can access the public key), require extra protection as their compromise can lead to unauthorized access.

Security Strength

AES offers reliable security, with key lengths of 128, 192, or 256 bits. The strength of AES encryption primarily depends on the key size, with longer keys providing higher security.

RSA security also relies on key length, with longer keys providing better protection. RSA is secure as long as keys are selected appropriately. Optimal key lengths range from 2048 to 4096 bits.

Use cases

AES is primarily used for data encryption, while RSA is for digital signatures. Together, they cover most of the digital encryption needs. Here’s where AES excels:

  • Data Encryption at Rest. AES encrypts sensitive data stored on devices or servers. For instance, when you lock your smartphone with a passcode.
  • Secure Communication within Closed Systems. In closed systems like messaging apps and Virtual Private Networks (VPNs), AES ensures the confidentiality of communication between users.
  • File and Disk Encryption. Many software and operating systems use AES encryption to secure files and disk drives.

And here are RSA’s applications:

  • Secure Internet Communication. The Transport Layer Security (previously Secure Sockets Layer) protocol uses RSA to protect sensitive data communication in transit between browsers and web servers. For instance, the padlock icon in your web browser indicates that RSA encryption protects your data during online transactions and secure web browsing.
  • Digital Signatures and Key Exchange. RSA is used to create digital signatures, which verify the authenticity and integrity of digital documents. For example, businesses use email SSL certificates to protect corporate communications and legal documentation.
Image by storyset on Freepik

How Do AES and RSA Work Together?

In some cases, AES and RSA work together to enhance security. For example, AES can encrypt the data, while RSA can encrypt and securely transmit the AES key. This way, even if an attacker intercepts the AES-encrypted data, they cannot decrypt it without the RSA-protected AES key. AES and RSA form a powerful encryption system that finds applications in the real world, like secure communication and data protection.

Secure Data Transmission

Here is how AES and RSA work together:

  1. AES encrypts the actual data.
  2. RSA securely exchanges the AES encryption key.
  3. The sender encrypts the AES key with the recipient’s public key.
  4. The intended recipient uses their private key to decrypt the AES key and then uses it to decode the actual data.

This combination of symmetric and asymmetric encryption ensures that only the intended recipient can access the data.

Real-World Applications

Now, let’s see what the AES and RSA encryption secure in the real world. Here are just a few applications:

  • When you make an online purchase or access your bank account online, RSA encryption protects your sensitive information during transmission, while AES secures data at rest on the bank’s servers.
  • Secure email services use RSA encryption to protect the contents of your emails. Attachments (file encryption) may be encrypted using AES encryption algorithms.
  • Governments use RSA encryption to secure online communications and protect classified information. AES secures data on government computers and storage devices.
  • Patient health records are often encrypted with AES when stored in electronic health record systems. Communication between healthcare providers relies on RSA encryption.

AES vs RSA Encryption Vulnerabilities

AES and RSA encryption can suffer from different vulnerabilities, and proper implementation is essential to protect the data.

Firstly, AES and RSA can be vulnerable to brute force attacks, where hackers use trial and error to guess the encryption key.

Secondly, both encryption methods can suffer from side-channel attacks, where an attacker can use information leaked from the system to guess the encryption key. Lastly, both encryption solutions can be vulnerable to improper implementation.

As for differences, AES encryption is vulnerable to attacks if its key is too short. Meanwhile, RSA encryption is susceptible to padding-oracle attacks, where the attacker can discover the key by sending different encrypted messages to the server and analyzing the responses.


Which is Better: AES vs RSA?

AES and RSA serve different purposes, so it’s not a matter of one being better. AES is more efficient for encrypting data at rest, while RSA is a secure method for sending data over the internet. The choice depends on the specific use case.

Which Is More Secure RSA vs AES?

RSA and AES serve different encryption purposes, and their security depends on key length and implementation. RSA excels in securing data in transit and key exchange through complex mathematical functions, while the AES symmetric encryption algorithm is efficient for data at rest. Both can offer high security when used correctly, but their effectiveness varies with the context and specific security needs.

Does HTTPS use RSA or AES?

HTTPS uses both RSA and AES. RSA exchanges keys during the initial connection setup, while AES encrypts the data transfer.

Can You Use RSA and AES Together?

Yes, RSA and AES can be used together for enhanced security. AES encrypts data, and RSA encrypts the AES key, protecting data.

Has RSA Been Cracked?

The RSA algorithm hasn’t been “cracked” in the sense that its underlying mathematics have been fundamentally compromised. However, advances in computational power, including quantum computing, pose potential threats to RSA encryption methods in the future.

Is AES Still the Best?

AES is still considered one of the best encryption algorithms used to encrypt data at rest due to its efficiency and strong security when using longer key lengths. The National Security Agency (NSA) is known to use and recommend the use of AES for securing sensitive information.

Does VPN Use AES Encryption?

Yes, VPNs often use the AES encryption method to secure data during transmission. It’s efficient and provides robust security.

Is RSA Encryption Outdated?

While the RSA encryption algorithm is still widely used, the field of cryptography is evolving to address potential quantum threats. Newer encryption methods are being developed to ensure data security in a post-quantum world.

Can RSA Be Decrypted?

RSA encryption can be decrypted with the private key, but this key is kept secret, making decrypting data by unauthorized parties extremely challenging. The security of the RSA algorithm depends on the key length, and advances in quantum computing could threaten RSA’s resistance to decryption in the future.

Can AES Be Decrypted?

AES encryption can technically be decrypted, but the practicality of doing so depends on the key length used. AES-128, AES-192, and AES-256 offer varying levels of security, with longer keys providing stronger protection. Decrypting AES encryption without the correct key is computationally infeasible, particularly when using longer key lengths like AES-256.


We’ve explained the difference between the AES and RSA algorithms and how they can complement each other for improved security. And, since no one-size-fits-all solution exists for today’s complex encryption needs, a strategic approach involves leveraging the strengths of AES and RSA.

AES and RSA encryptions have different advantages and disadvantages. AES is faster and simpler to use, while RSA provides more complex security that can withstand more rigorous attacks.

As technology advances, data encryption must evolve to address new threats. RSA vs AES encryptions, while strong in their own right, face vulnerabilities and challenges in the era of quantum computing. AES may require longer key lengths to maintain security, while RSA’s future lies in transitioning to quantum-resistant encryption.

Save 10% on SSL Certificates when ordering today!

Fast issuance, strong encryption, 99.99% browser trust, dedicated support, and 25-day money-back guarantee. Coupon code: SAVE10