Difference between public key and private key

In this article, we are going to discuss public key, private key and the difference between them. Private keys and public keys both terms are commonly used for encryption and decryption. So, it is very important to know about both keys and the difference between them.

Public key

It is an encryption technique that uses a pair of keys (public and private key) for secure data communication. In the pair of keys, the public key is for encrypting the plain text to convert it into ciphertext, and the private key is used for decrypting the ciphertext to read the message.

The private key is given to the receiver while the public key is provided to the public. Public Key Cryptography is also known as asymmetric cryptography.

The public key can be shared without compromising the security of the private one. All asymmetric key pairs are unique, so a message encrypted with a public key can only be read by the person who has the corresponding private key. The keys in the pair have much longer than those used in symmetric cryptography. So, it is hard to decipher the private key from its public counterpart. Many of us, heard about RSA, which is the most common algorithm for asymmetric encryption in use today.

Public-key encryption is slower than secret-key encryption. In secret key encryption, a single shared key is used to encrypt and decrypt the message, while in public-key encryption, different two keys are used, both related to each other by a complex mathematical process. Therefore, we can say that encryption and decryption take more time in public-key encryption.

Applications of public key

The applications of public key are -

Public key cryptography can be used to encrypt Emails to keep their content confidential.
Asymmetric cryptography or public-key cryptography is also used in Secure socket layer (SSL) protocol to make secure connections to websites.
Public key is also used in Blockchain and cryptography technology. For example, a pair of keys is generated, while setting up a new cryptocurrency wallet.
It can be used to create a digital signature in the Operating System software such as Ubuntu, Red Hat Linux packages distribution, etc.

Private Key

In private key, the same key (or secret key) is used by both the parties, i.e., the sender and receiver, for Encryption/Decryption technique.

The sender uses the secret key and encryption algorithm for encryption, whereas for decryption, the receiver uses this key and decryption algorithm. In Secret Key Encryption/Decryption technique, the algorithm used for encryption is the inverse of the algorithm used for decryption. It means that if the combination of addition and multiplication is used in the encryption algorithm, then the decryption algorithm will use the combination of subtraction and division.

The secret key encryption algorithm is also known as symmetric encryption algorithm because the same secret key is used in bidirectional communication. The mechanism of private key is faster than the mechanism of public-key cryptography. The reason for this is that the size of the key is small.

Public key v/s Private key

That's about the description of both public and private keys. Now, let's see the comparison chart between both keys. We are comparing both keys based on some characteristics.

On the basis of	Public key	Private key
Definition	It is defined as the technique that uses two different keys for encryption and decryption.	It is defined as the technique that uses a single shared key (secret key) to encrypt and decrypt the message.
Known as	It is also called as Asymmetric key encryption.	It is also called as symmetric key encryption. It is because the same secret key is used in bidirectional communication.
Efficiency	It is inefficient as this technique is used only for short messages.	It is efficient as this technique is recommended for large amounts of text.
Speed	It is slower as it uses two different keys; both keys are related to each other through the complicated mathematical process.	It is faster as it uses a single key for encryption and decryption.
Secret	It is free to use.	Apart from the sender and receiver, the private key is kept secret and not public to anyone.
Purpose	The main purpose of the public key algorithm is to share the keys securely.	The main purpose of the secret key algorithm is to transmit the bulk data.
Loss of key	There is a less possibility of key loss, as the key held publicly.	There is a possibility of losing the key that renders the system void.