Difference Between Public Key and Private Key

By Rushali Shome

If you have a basic knowledge of how some of the most common and widely used cryptographic algorithms function, you would know that Bitcoin and most other spin offs of the same that use a similar model of encryption, make use of something called the asymmetric encryption.

Even if you do not know the nitty gritty of an asymmetric encryption, you have probably heard of the terms “public key” and “private key“. What are they? How are they different? Why do we need them at all?

We break all of these things down for you in this article, so you get the difference between the two. However, let’s get some of the definitions out of the way first.

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Defining Terms Related to Private and Public Key Encryption

What is Encryption?

Encryption refers to a process whereby you disguise sensitive information that you need to transmit, so that any person besides the intended recipient cannot read or decode its contents. This is a primary term related to security and privacy in the age of the internet.

What is Decryption?

When an encrypted packet of message finally reaches the intended recipient, he or she should be able to uncover the disguise and read the contents. Now, in cryptography, these contents are usually converted into codes with the help of specific algorithms. The process of uncovering the contents by decoding the message is called decryption.

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What is Asymmetric Encryption?

Asymmetric Encryption refers to the process whereby a data packet is protected by using one public key for encryption and one private key for decryption. Several cryptographic algorithms make use of this form of encryption. One of the most common and well-known ones that use it is called the RSA or the Rivest-Adi-Shamir algorithm.

What is Public Key?

The public key is the visible address of the recipient the given data packet is meant for. The public key is available for everyone to view and access in a public domain.

What is Private Key?

To be able to unlock the package, the recipient must use the corresponding private key that goes with the public key. Without the private key, the message is therefore worthless as it cannot be decoded without it.

Difference Between Public Key and Private Key: How they Work

To explain how they work and how they are different, we must use an analogy.

For example, you are Bill and you are sending a data packet full of sensitive documents to your friend Tina. Now, you address to the proper address of Tina’s residence. It is not too hard to find out where she lives as the information is available in the town’s directory. Therefore, Tina’s address works exactly like a public key. Now, the postman delivers the data packets into Tina’s letter box. To open it, you must use a specific combination of numbers or use a special key that only Tina has access to. This is the private key. Only when she uses this, can she access the documents and derive meaning from it.

Thus, while public key is meant for encryption, private key is meant for decryption. The former is visible to all while the latter is known to just one: the recipient. The public key turns plaintext to ciphertext (coded text) and the private key does the exact opposite.

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Rushali Shome

Rushali Shome is a history undergraduate with a keen interest in puns, politics and beyond. When not typing away furiously in the “Notes” section of her phone, she can be found trying to catch the eye of servers at restaurants or weddings for a second helping.

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