In this detailed guide, we discuss the RSA cryptosystem as well as RSA security, how it works, and what it does. RSA which stands for Rivest–Shamir–Adleman is a widely used encryption algorithm. Unlike some other prominent encryption algorithms and protocols, RSA relies on asymmetric cryptographic standards. Since it relies on asymmetric cryptography or public key cryptography, RSA encryption always involves a pair of two different keys.

One of these keys is kept private while the other is public and it can be shared. In this sense, RSA encryption involves a private and public key. The public key that is known is used for encrypting messages and the private key is used for decrypted messages that have been encrypted. The RSA cryptosystem for encrypting and decrypting messages was resigned by Leonard Adleman, Adi Shamir, and Ron Rivest back in 1977. Before we take a look at RSA security and how it works, we should examine other RSA cryptosystem essentials to see how it works.

**What is RSA Encryption?**

Over four decades after its original release, the powerful RSA algorithm and cryptosystem remains one of the most used cryptography protocols in the world. Despite the fact it is quite old, RSA security remains top-notch even when compared to more modern encryption technologies and protocols. In fact, this cryptography algorithm forms the basis of many other cryptographic algorithms.

Before its first official publication, a secret encryption system was developed back in 1973 at the British signals intelligence agency by Clifford Cooks. At the time, RSA encryption solves one of the major cryptography issues that revolved around sharing coded messages when you cannot share the required code. This was made possible with the RSA encryption algorithm that remains one of the most widely used asymmetric encryption protocols.

As previously mentioned, RSA security revolves around two different keys. This is one of the major differences between symmetric and asymmetric encryption protocols. RSA encryption involves a private and a public key and these are always complimentary. In other words, a secret message that is encrypted with a specific key can only be successfully decrypted by the key’s counterpart. While public keys are known to the public, private keys are secret.

**What About the RSA Security?**

RSA encryption as well as many other similar asymmetric cryptography protocols and algorithms are used for assigning digital signatures. When the RSA encryption algorithm is used for digital signatures, RSA fingerprint encryption is incorporated into the file. This is what enables the receiver to verify the integrity of the file. When it comes to RSA security, it primarily relies on integer factorization.

A message that is RSA encrypted is looked at as a single large number. RSA users both create and publish RSA public keys that are treated like two large numbers alongside their auxiliary values. These large prime numbers are secret. While everyone can RSA encrypt messages using public keys shown as large prime numbers, they can only be decrypted by individuals who know the required private keys or who know the required prime numbers.

In this sense, the RSA security is based on factorizing the message, key generation, key distribution, encryption, and finally decryption. In other words, the RSA security and algorithm always involves four steps, and breaking the RSA encryption cannot be done without factorizing the product.

- Key generation
- Key distribution
- Encryption
- Decryption

**Key Generation**

The RSA security relies on four steps and the very first step is key generation. As previously mentioned, two keys are always involved including a private and a public key. Public keys are used for encrypting while private keys are used for decrypting messages. Public keys are listed as the n and e integers and private keys are represented as the d integer. The RSA algorithm keys are generated randomly.

For greater security, two different prime numbers are chosen and these will be kept secret. Computing these two integers creates the public key represented by the n integer. When it comes to the second part of the public key represented by the e integer, the most widely used value is 65,537. Every public key in RSA encryption features the public exponent depicted as e and the modulus depicted as n. The private key is represented as the d integer which is represented by the e modulus modular multiplicative inverse.

In the RSA algorithm, private keys can also be computed by the Extended Euclidean algorithm. As private key exponents, the d integer is also kept secret. As mentioned, the RSA security also relies on key distribution. Suppose someone wants to send an encrypted message to a friend. If the messages is RSA encrypted, the sender must know the recipient’s public key in order to successfully encrypt the message while and the sender must use his or her private key to decrypt the received message.

**RSA Security – Encryption and Decryption**

When it comes to the RSA security and the process of encrypting and decrypting the message. In order to enable the sender to encrypt his or her message, the receiver of the message transmits his or her key represented by the n and e. The key is transmitted via some reliable route while the private key represented by d is never transmitted. Once the sender of the message gets the receiver’s public key, he or she can finally send the message.

Relying on modular exponentiation, the sender turns the message which appears in a form of an un-padded plaintext into a long integer represented as m. In other words, the un-padded message via padding scheme turns into a padded plaintext. The next step is to compute the ciphertext and for this, the receiver’s public key is required. Once done, the sender transmits the ciphertext to the receiver.

The receiver can recover the message with his or her private key represented as d. The original un-padded plaintext message is recovered by the padding scheme reversal. The major difference between symmetric and public-key encryption (RSA encryption) is that symmetric-key encryption relies on the same private key for encrypting and decrypting. This makes RSA encryption and other public-key encryption very useful when there has been no safe opportunity to share keys.

When combined with other encryption algorithms, RSA encryption is also used for assigning digital signatures that prove the integrity and authenticity of encrypted messages. However, it is not widely used for encrypting files..

Instead, the RSA security is boosted with symmetric-key algorithms. In these cases, files are encrypted with symmetric-key algorithms and then symmetric keys are RSA encrypted. While there are many different encryption algorithms out there, RSA encryption is still widely used in email security, web browsers, VPNs, and other communication routes. RSA algorithm is also the foundation for PGP and TLS encryption.