Difference Between Public Key and Private Key in Cryptography

The main difference between public key and private key in cryptography is that the public key is used for data encryption while the private key is used for data decryption.

The public key and private key are two locking mechanisms used in asymmetric encryption of cryptography. Public key is a type of lock used with an encryption algorithm to convert the message to an unreadable form. Private key is a type of lock used with a decryption algorithm to convert the received message back to the original message. Both these keys help to ensure the security of the exchanged data. In brief, a message encrypted with the public key cannot be decrypted without using the corresponding private key.

Key Areas Covered

1. What is Cryptography
     – Definition, Functionality
2. What is Public Key 
     – Definition, Functionality
3. What is Private Key 
     – Definition, Functionality
4. Difference Between Public Key and Private Key in Cryptography
     – Comparison of Key Differences

Key Terms

Cryptography, Public Key, Private Key

What is Cryptography

Cryptography is a process that allows making the data secure in communication. For example, in online transactions, it is important to protect the personal details. Cryptography is a solution to protect data. There are two main concepts in cryptography called encryption and decryption. At the sender’s end, the original message is transformed into an unreadable message. This is called encryption. This uses an algorithm and a key. This converted message is also called a ciphertext and it is sent via the network. At the receiver’s end, the message is transformed back into the original message. This is called decryption. It also uses an algorithm and a key.

There are two techniques used in encryption and decryption. They are the symmetric and asymmetric encryption. Symmetric Encryption uses the same key for encryption and decryption. It is fast but requires a secure channel. On the other hand, asymmetric encryption uses two keys called public key and private key for encryption and decryption. It is more secure than symmetric encryption. 

Figure 1: Public and Private Key

What is Public Key

The public key is used to accomplish encryption. When the data is encrypted using the public key, it is done in a way that leaves a large number of possible solutions available. To decrypt the data, it is necessary to test all the possibilities before finding the correct one. When there is a private key, there is only one way to decrypt the message. Even though public key helps the encryption process, it does not help decryption.

What is Private Key

The private key is used to accomplish decryption. In other words, it is not possible to decrypt the received message without the corresponding private key. The message can be encrypted without the private key. But it is necessary in decryption. The private key is not transferred and it is not intercepted by any other unauthorized third party. The public key is widely distributed, but the private key is kept hidden.

Difference Between Public Key and Private Key in Cryptography

Definition

Public Key is a type of lock used in asymmetric encryption that is used with an encryption algorithm to convert the message to an unreadable form. Private key is a type of lock used in asymmetric encryption that is used with a decryption algorithm to convert the received message back to the original message. 

Main Task

While public key is used to encrypt the message, private key is used to decrypt the message.

Type

Furthermore, the pubic key is widely distributed while private key is kept secret.

Conclusion

The public key and private key are used in asymmetric encryption of cryptography. Unlike in symmetric cryptography, it is more secure and reliable as it uses two keys public and private for encryption and decryption. The main difference between public key and private key in cryptography is that the public key is used for data encryption while private key is used for data decryption.

Reference:                                                  

1. Symmetric Key and Public Key Encryption, Itfreetraining, 18 June 2013, Available here.

Image Courtesy:

1. “Orange blue public key cryptography en” By Bananenfalter – Own work (CC0) via Commons Wikimedia