RSA Encryption and RSA Algorithm: A Comprehensive Overview

RSA (Rivest-Shamir-Adleman) is an encryption algorithm that’s commonly used to securely transmit data on the internet. It also has applications in software protection and digital signatures.


RSA uses a public key for encryption and a private key for decryption. The algorithm carries the names of Ron Rivest, Adi Shamir, and Leonard Adleman, its inventors. 


Here, we’ll discuss how RSA encryption works and its advantages, and real-life applications.

Where is RSA Encryption Used?

RSA encryption is used to provide authenticity for internet messaging. It has applications in digital signatures, secure communication protocols (like SSH and HTTPS), encrypting email messages, virtual private networks, and software protection.


However, it’s rarely used as a standalone encryption method as it can be resource intensive. Often, it’s utilized in combination with other encryption methods. 

Advantages of RSA

RSA is widely regarded as a strong and efficient encryption algorithm. Some of the advantages of RSA encryption include:

  • Authentication: Provides public and private keys for message encryption and user authentication.
  • Keys aren’t shared: The RSA encryption doesn’t require key sharing, providing additional security.
  • Fast: RSA encryption is faster relative to other encryption methods like DSA.
  • Preserves data integrity: The data can’t be changed as it moves from one user to another.

The Background of RSA Encryption

Before the emergence of public-key encryption technologies, it was virtually impossible to maintain security in internet communications. 


In 1970, James H. Ellis published a big step forward in cryptography in a secret GCHQ internal report "The Possibility of Secure Non-Secret Digital Encryption". He was the first researcher to hint at the possibility of non-secret encryption that uses a public key, and his findings were later expanded by his colleague, Clifford Cocks.


Later, Malcolm J. Williamson, a researcher at GCHQ, invented the Diffie-Hellman key exchange, the first method that allowed for secure key sharing regardless of whether the channel was monitored by adversaries. 


His work was classified until it was made public in 1997. Later, it was revealed that there was an RSA algorithm patent that was registered in 1983 by MIT, and since the early days of mainstream internet access, the RSA algorithm has seen widespread use as a key security tool.

RSA Vs Diffie-Hellman

The primary difference between RSA and Diffie-Hellman is the exchange algorithm. RSA uses public and private keys for encryption and decryption, while Diffie-Hellman enables the sender and receiver to exchange a secret key securely through a public communication channel.

Advantages of RSA include:

  • Higher security 
  • Provides authentication
  • Used in encryption and digital signatures 
  • Easier to implement 

On the other hand, Diffie-Hellman is:

  • Faster and more efficient 
  • Not vulnerable to quantum attacks


In short, RSA is more secure because it provides authentication, while Diffie-Hellman is just a key exchange method.

How Do You Create RSA Encryption?

The RSA encryption process typically goes as follows:

  1. The plaintext is converted into an array of bytes.
  2. Bytes are converted into a large integers.
  3. A public key is used to create a cipher that’s only decrypted with a private key.
  4. The RSA public key is imported with a script.
  5. The recipient uses their private key to decrypt and read the message.


The Python RSA library in the Python programming language makes the encryption process easier. Other RSA libraries or packages for RSA encryption include OpenSSL (Ruby), Crypto++ (C++), and the Java cryptography API (Java). 

How Does RSA Encryption Work?

Here’s how the RSA encryption process goes:

  1. A trapdoor function is used to generate 2 large prime numbers with a primality test.
  2. The message is assigned a public and private key by factoring the prime numbers created by the trapdoor function.
  3. The message is decrypted with the private key.

What Are the Applications of RSA Encryption?

Some of the most common applications of RSA encryption are: 

  • Creating coded transmissions or messages.
  • Used with other encryption methods to enhance security.
  • Used to secure internet-enabled software to protect data.
  • Securing the connection between VPN servers and clients.

How RSA Encryption Works in Practice?

These are some real-world examples that demonstrate the usage of RSA encryption in practice:

  • Securing email messages in email providers.
  • Encrypting messages in messaging apps and chat rooms.
  • Securing P2P data transfer.
  • Securing the connection between web browsers and servers.

How are more Complicated Messages Encrypted with RSA?

There are multiple ways to encrypt complicated messages like large data with RSA encryption. One method is to use multiple RSA keys for encryption. Another technique is to utilize hybrid encryption by combining RSA encryption with another encryption algorithm like DSA.


It’s also worth mentioning that complex messages are ideally encrypted using much larger prime numbers for additional security. 

RSA Security & Attacks

Some of the major threats to RSA include:

  • Smaller keys can be cracked easily with factoring and brute forcing (can be prevented by using at least 1024 bits keys).
  • Side channel attacks: Used to assist in breaking RSA by providing information from its implementation.
  • Timing attacks: the attacker may be able to find the private key if they measured the amount of time needed to decrypt the message (can be prevented with cryptographic blinding).

Is RSA Encryption Safe for the Future?

RSA encryption is generally considered safe for the future as long as it’s implemented properly, even if threats exist. To get the best security from RSA encryption, use 1024, 2048, or 4096 bits keys, depending on the severity of your threat models.

Will Quantum Computing Affect RSA?

It’s widely predicted that quantum computing will render RSA encryption, in its current form, useless. 


Quantum computers are capable of solving complex mathematical problems that serve as the basis of RSA encryption. 


Nevertheless, research is currently underway to find new public key algorithms that are resistant to quantum computing. Lattice-based and multivariate encryption methods are quantum-based and may see a more widespread use than RSA encryption in a post-quantum world.


That was everything you needed to know about RSA encryption. 


For more about encryption algorithms and methods, check out these posts on the CyberTalents blog:


We also encourage you to check out our Cryptography challenges to enhance your technical skills.