What is RSA encryption?

RSA encryption is one of the most widely used methods of asymmetric encryption, where a pair of keys - one public and one private - are used to encrypt and decrypt data. The technology is widely used to secure sensitive data across digital communication channels, such as in secure emails, digital signatures and encrypted connections like TLS/SSL in web browsers.

RSA is based on the mathematical challenge of factorising large prime numbers. When two very large prime numbers are multiplied together, they create a product that acts as a central part of the encryption. While it's easy to multiply the numbers together, it's extremely difficult to find the original prime numbers from the product alone. This makes it virtually impossible for hackers to decrypt data without the private key.

The encryption process in RSA

RSA works by generating a key pair that is used to protect information. First, two large prime numbers are selected and multiplied together to form a modulus that is part of both the public and private key. When a sender wants to send a secure message, they use the recipient's public key to encrypt it. Only the recipient's private key can then decrypt the message and make it readable.

In addition to protecting communications, RSA is also used for digital signatures, where the sender signs a message with their private key. The recipient can then verify the signature with the sender's public key, ensuring that the message is authentic and has not been altered along the way. This method is often used in official documents, software updates and financial transactions.

Pros and cons of RSA

RSA is one of the most secure and widely used encryption methods, especially because it enables secure communication without the need to share a secret key beforehand. This makes it particularly useful for online payments, digital signatures and secure data transfer. At the same time, RSA ensures that data cannot be altered or intercepted during transmission.

Advantages:

• High security: The asymmetric encryption makes it extremely difficult to decrypt data without the private key.
• No need for prior key exchange: The public key can be freely shared, while the private key remains secret.
• Wide application: RSA is used in everything from digital signatures to encrypted connections in web browsers and financial systems.
• Ensures data integrity: Digital signatures guarantee that data has not been altered in transit and that the sender is authentic.

While RSA is a strong and reliable encryption method, it also has certain drawbacks that can affect its usefulness in certain situations.

Disadvantages:

• Slow computation time: RSA requires large computations and is significantly slower than symmetric encryption methods like AES.
• Large key sizes: To maintain security, very long keys (2048 bits or more) are required, which increases processing time.
• Limited to small amounts of data: Due to the heavy computations, RSA is most often used to encrypt keys rather than large data sets.
• Vulnerable to quantum computing: Future quantum computers could potentially break RSA encryption, which has led to the development of post-quantum cryptography.

Despite these challenges, RSA remains one of the most reliable encryption methods, especially in situations where secure key exchange and digital signatures are essential.

Application areas for RSA encryption

RSA is widely used in digital systems where secure communication and authentication is needed. For example, it is used in TLS/SSL certificates that secure encrypted connections between users and websites, in email encryption where it protects sensitive messages, and in digital signatures where it ensures the authenticity of documents and software updates. Many messaging services also use RSA to exchange encryption keys, with faster symmetric methods like AES taking over.

FAQ - Frequently asked questions