# RSA Cryptography: history and uses

The RSA encryption is a public-key-based cryptosystem, named after Ron Rivest, Adi Shamir and Len Adleman who invented it in 1977.

Clifford Cock had previously invented an equivalent system for the British GCHQ back in 1973. This project remained secret until 1997.

The RSA cryptosystem is the most widely-used public key cryptography algorithm in the world. You can use it to encrypt a message without the need to exchange a secret key separately.

Its algorithm can be used for both public key encryption and digital signatures. Its security is based on the difficulty of solving certain mathematical problems such as factoring large integers.

## RSA cryptography: what is it and how does it work

RSA is one of the first practical public-key cryptosystems and is widely used for secure data transmission. In such a cryptosystem, the encryption key is public and differs from the decryption key which is kept secret.

The idea of asymmetric cryptography first came out in Hellman and Whitfield Diffie’s essay New Directions in Cryptography in 1976. It introduced  the radical idea of distributing cryptographic keys.  It has become known as Diffie-Hellman-Merkle key exchange.

Generally, a public encryption method relies on a public encryption algorithm, a public decryption algorithm, and a public encryption key. Using the public key and encryption algorithm, anyone can encrypt a message.

In other words, anyone could see the public encryption key to encrypt a message. But the actual decryption can happen by the means of the private key only, which is kept secret.

But how does the RSA work then?

Alice sends an encrypted message to Bob without any prior exchange of secret keys.  Alice uses Bob’s public key to encrypt the message and Bob decrypts it using the private key, which only he knows.

Furthermore, you can use RSA to sign a message, so Alice can sign a message using their private key and Bob can verify it using Alice’s public key.

## Uses and Security

Common uses of the RSA algorithm range from hybrid encryption schemes and digital signatures.
In the first case, it  encrypts a symmetric key and send it to a second party. It is advantageous system that secure key transmission.

However, there are disadvantages too. The RSA scores high in slowness compared to other encryption systems. It is not convenient then to use it to encrypt a whole file.

Instead, you can use a symmetric system whose key is encrypted by RSA directly.

Concerning digital signatures, a party in a communication can use the private key to sign the cryptographic hash of the message/file.

By doing so, the  second party has the corresponding public key he or she can verify that the file is authentic and that no alternation has taken place.

Many industries use this technology for doing business. For instance, banking uses it to protect data such as costumer information and transactions record. In e-commerce, furthermore, it is useful to encrypt user identity in transaction.