Difference between public key and private key cryptography in Cryptology

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What is public and private key cryptography?

There are two main concepts in cryptography: encryption and decryption. Encryption is the transformation of the original message into unreadable, i.e. encrypted. Decryption is the transformation of an encrypted message back into its original form. The algorithm and key are used for both encryption and decryption, and there are two encryption and decryption methods: symmetric and asymmetric encryption. Symmetric encryption, also called private key encryption, has been known to mankind for a very long time. On the other hand, asymmetric encryption, also called public key encryption, only came into existence in the 1970s and became really widespread as the Internet developed.

What is Private Key Encryption?

Private key encryption is a very popular, simple and effective encryption system. This allows both encryption and decryption to be performed using the same key. Since anyone with the key can decrypt the information encrypted in this way, this key must be kept secret and accessible only to the sender and recipient of the information. That is why it is called private key and the encryption system itself is called private key encryption.

What is Public Key Encryption?

This encryption system is much more complex, it only uses the private key to decrypt the message. To encrypt the same message, a separate public key derived from the public key is used. If a person knows the private key, he can calculate the public key. However, knowing only the public key is not enough to calculate the private key. This is why the public key does not need to be kept secret, since knowing it does not allow the encrypted information to be decrypted.

How does public and private key encryption work?

In private key cryptography, the sender encrypts a message with the private key and sends it to the recipient. In order for the recipient to decrypt the message, they would need the sender to provide the same private key through a well-secured channel, which reduces the security of such cryptographic systems.

In public key cryptography, the sender of a message encrypts the message with the public key and sends it to the recipient. The recipient of the message receives it and decrypts it with a private key that only they have. Because only the recipient needs the private key in this encryption system, it does not need to be sent, making it more secure. In public-key cryptography, only the recipient—not even the sender—can decrypt the message.

Advantages and disadvantages of public key cryptography

Let’s look at the advantages and disadvantages of these encryption systems by comparing them.

Comparison of private and public key cryptography

	Private key cryptography	Public key cryptography
Encryption-decryption speed	Faster	Slow down
Required processing power	Less	More
You need to send the private key over a secure channel	Yes	Not
Key length	shorter	longer
Parties who need to know the private key	Recipients and senders	Recipients only
Complexity of key management in a large network	High	Short
Can be used to create an electronic digital signature	Not	Yes

In this comparison, we can see that although private key encryption is much simpler and faster, it is not suitable for blockchain networks.

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