What is an RSA Certificate?

What is an RSA Certificate?

Don’t be confused with RSA as a certificate as it’s a key and algorithm used in SSL/TLS certificates. However, sometimes RSA is referred to as an RSA certificate. RSA (Rivest–Shamir–Adleman) is an algorithm that is used to encrypt and decrypt data.

Your digital infrastructure needs strong security, and while you are seeking security solutions for securing your web, the first choice, which is recommended, by web developers and security experts is to install SSL/TLS certificates. These digital security certificates secure your web with encryption algorithms to safeguard your site data against intruders.

While you are installing these certificates for your site security, you may face some undisclosed terminologies, which are new to you and can confuse your mind. One such term visible on SSL certificates is the “RSA Algorithm” which is also named “RSA certificate”.

In this blog, we are here to discuss everything about the RSA algorithm used in SSL certificates, their functioning process, and the encryption security it offers in the digital world.

So, let us get rolling.

What is an RSA Certificate?

When you hear the term RSA certificate, it means that the concerned is talking about the RSA algorithms used in the SSL/TLS certificate. The acronym RSA stands for the last names of the three individuals who developed the cryptographic algorithm: Rivest, Shamir, and Adleman.

RSA (Rivest–Shamir–Adleman) algorithm encrypts/decrypts sensitive data with the use of cryptography. Mathematicians Rivest, Shamir, and Adleman discovered this cryptographic algorithm in the year 1978, and hence their initials were used to derive the name of this algorithm.

The main motto of this algorithm is data encryption, wherein plain and readable text is converted into a cipher and non-readable format. In short, encryption converts the text into gibberish and coded format. Deciphering this format is a tough task for hackers.

What is RSA Certificate used for?

  • Encrypt communication: RSA secures communication between two parties.
  • Code Signing Certificates: RSA is used to authenticate and ensure the integrity of the code.
  • VPNs: VPNs use RSA to encrypt communication between two parties and validate identities.
  • Email: Some email clients and servers are using RSA to secure email communication.
  • Data and file security: RSA is used to encrypt files and data to secure them against unauthorized access.

Previously, such encrypted communications were used for securing defense information and pivotal government communications. However, the rapid rise of internet usage has made a certificate an essential need.

RSA algorithms use asymmetric encryption, which is incorporated in RSA (SSL) certificates too.

Oops! Are you ignorant about asymmetric encryption too?

Well, we can enlighten you regarding the same, because if you are unaware of it, you will never be able to understand the concept of RSA.

RSA: The Most Popular Asymmetric Encryption Algorithm:

RSA is a well-known term in cryptography and as stated earlier, this cryptographic algorithm uses asymmetric encryption (public-key cryptography) to encrypt sensitive data for keeping it secure from intruders.

In the modern era, data encryption is the pillar of digital security. Encryption keys are required to encrypt the data. Two types of encryptions are carried out using these encryption keys.

Symmetric Encryption: Symmetric encryption uses only one key for encrypting/decrypting the information.

Asymmetric Encryption: Asymmetric encryption uses two keys for encrypting and decrypting the information. The keys are termed the public key and the private key. These keys are mathematically linked with each other.

Here, the data is encrypted with one key and decrypted with the other.

The public key is accessible to users (public) who wish to send an encrypted message, whereas, the private key is secretly accessible to the recipient of the message only.

Example: In sites having SSL certificates, the data is encrypted by the public key, and is later decrypted by the private key, which is secretly stored on the server.

Thus, SSL certificates ensure:

  • Data Authentication – wherein the intended recipient views the data only.
  • Data Encryption – Wherein the encrypted data is secured since, it can be decrypted only with the private key, thus preventing data theft.
  • Data Integrity – wherein the recipient is assured about the originality of the data and its non-tampering.

This makes SSL certificates (public key encryption) more desirable and acceptable as a security solution in the digital market.

How does the RSA Algorithm Work?

Have you ever heard of the prime factorization method?

No? The prime factorization expresses a number as a product of its prime factors.


Number =20, and we all know that 5×4 = 20. However, 4 is not a prime number. It can be factorized into 2×2. So, the prime factorization of 20 = 5×2×2.

The functioning of the RSA algorithm is based on this prime factorization method. In short, this method is utilized for the encryption and decryption of information.

It functions by factoring a huge integer. This integer is based on the product of large prime numbers (Z = X × Y) which are selected randomly. Though the product (Z) can be easily determined, finding out the 2 prime numbers (X, and Y) used for gaining the product is an impossible task. Even supercomputers fail in factorizing and detecting these numbers.

So RSA functions on the thought that though finding the product is an easy task, finding the original prime numbers by factorizing the same is an impossible task.

Are you aware of the most intricate part of RSA cryptography?

The algorithm is used for generating both the keys for the functioning of the encryption process.


Suppose the prime numbers you guess are 1-20 and name them as X and Y and they are generated by using the Rabin-Miller primality test algorithm. Upon multiplying the prime numbers both, you will have a modulus (Z). If someone says, to find X and Y numbers using Z modulus then, it will be an easy task. However, if Z is a very large number then, it will be difficult to retrieve both X and Y numbers. This is called Prime Factorization. This modulus is used in both the public and private keys. The length of the keys, which is determined in bits, is termed “key length”.

The key length of RSA keys is 1024 bits or 2048 bits, which is impossible to factorize. However, since hackers have started breaking 1024-bit keys, the use of 2048-bit keys for strong encryption security is ideal.

The NIST (National Institute of Standards and Technology) thus suggests a minimum RSA key length of 2048 bits, thus making the RSA algorithm safe. All the digital security certificates (SSL and TLS) provide 2048-bit CSR encryption for securing your site.

Is RSA Certificate Safe? Has the RSA Algorithm been Broken?

There is confusion amongst digital owners regarding RSA certificates and the security they provide. RSA security solely depends on the toughness of factoring huge integers.

The strength of the RSA algorithm is directly proportional to the key length, i.e., the larger the key size, the stronger the algorithm. In short, it is impossible to break an algorithm that has a large key size.

In 2009, a team broke into a 768-bit RSA key via factoring with the help of multiple computers. In the modern era, there has been a phenomenal rise in the strength of the RSA keys (2048-bit); hence, the possibility of cracking a large key is also possible. A lot of time, money, and other resources are required for the same, which prevents hackers’ intervention.

However, since RSA uses a 2048-bit key length, it is considered the most trusted and secured asymmetric algorithm in today’s digital era.

Wrapping Up:

The rise in computing power has compelled mathematicians to come up with better algorithms that can factor larger numbers.

The strength of the encryption depends on the key size. If the key size is doubled, the encryption strength becomes stronger.

Hackers are using varied techniques to penetrate websites. Companies are now finding substitutes for RSA, and are moving forward to implement Elliptic Curve Cryptography (ECC) algorithms. Hardware and software implementing ECC systems have started storming the digital security market.

Research indicates that RSA may be alternated with new algorithms by the end of this decade.

However, at present, RSA is safe and ideal for securing your digital infrastructure from hackers.

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