Private and public keys are two keys we use in the cryptosystem to secure information. In symmetric cryptography, we only use a private key that both communicating parties share. However, in asymmetric cryptography, each party has two keys, a public key accessible to all the other parties and a private key is only accessible by its owner. The asymmetric algorithm’s exact transformation depends on the public and private keys provided as input.
What is a Key in Cryptography?
Key plays a vital role in the study of cryptography. Cryptography is a study of techniques ensuring shared information’s secrecy and authenticity. On the basis of how many numbers of keys a cryptographic system involves, we can broadly classify cryptographic approaches into two types:
- Symmetric encryption
- Asymmetric encryption
If the sender and receiver use a single shared key for encryption and decryption, we refer to the cryptographic system as symmetric encryption. We refer to the cryptographic system as asymmetric encryption if the sender and receiver use two different keys.
A key is provided as an input to encryption or decryption algorithms. Its value is independent of the plain text and of the algorithm. The key helps the algorithm alter the plain text to produce a scrambled message that we refer to as cipher text.
However, we study many types of keys under cryptography, but in this particular content, we will identify differences between private and public keys. So, let’s start.
Content: Private Key Vs Public Key
Comparison Chart
| Basis for Comparison | Private Key | Public Key |
|---|---|---|
| Use | Used in both symmetric and asymmetric encryption | Used only in asymmetric encryption |
| Accessibility | In Symmetric encryption, a single private key is shared between two authentic communicating parties. In asymmetric encryption, every user has its own unique private key. | In the asymmetric encryption technique, every participant has their own public key, which is accessible to all. |
| Encryption/Decryption | In symmetric encryption, the private key is used to encrypt and decrypt the message. In asymmetric encryption, the recipient’s private key is only used to decrypt the received message. | In asymmetric encryption, public key of the recipient is used to encrypt the message. |
| Speed | Symmetric encryption technique using one common private key is faster. | Asymmetric encryption technique using public and private keys is slower. |
| Applicable | Symmetric encryption technique, one common private key, is used to encrypt huge amounts of data. | Asymmetric encryption technique using a public key mechanism is used only for short messages. |
| Example | With symmetric encryption private key is used to secure the hard drive and other storage device’s content. | In asymmetric encryption, the public key mechanism is used to secure web sessions, emails, online chats etc. |
What is a Private Key?
Based on the number of keys used, we classify cryptographic approaches into two: symmetric cryptography and asymmetric cryptography. The concept of the private key is different in symmetric and asymmetric cryptography.
In symmetric encryption, the sender and receiver both share a single private key. Sender uses the private key to perform encryption on the message and forward it to the receiver. The recipient uses the same private key at the receiver end to decrypt the message.
However, in asymmetric encryption, every participant has their own private. The recipient of the message uses its private key to decrypt the messages they receive.
To avoid confusion between the private key of symmetric and asymmetric encryption, we refer to the private key of symmetric encryption as a secret key.
What is Public Key?
Symmetric encryption does not involve the concept of public key. However, asymmetric encryption is a form of cryptosystem where two different keys perform encryption and decryption. These two keys are the public key and the private key.
Every participant has a pair of public and private keys. The public key is accessible to all the other participants. However, the private key is only accessible by its owner. Sender uses the recipient’s public key to encrypt the message. When a message reaches the recipient, it uses its private key to decrypt the message.
Key Differences Between Private and Public Key
- A private key is used in symmetric and asymmetric encryption, while the public key is used only in asymmetric encryption.
- In symmetric encryption, two authentic communicating parties share a single private key. While in asymmetric encryption, every participant has their own private key, and there is no sharing of the private key. If we talk of a public key, we don’t have the concept of the public key in symmetric encryption. However, in asymmetric encryption, every participant has their own public key, which is available to all the participants.
- In symmetric encryption, the private key is for both encrypting as well as decrypting the message, while in asymmetric encryption, we use the private key only to decrypt the received message. In the case of the public key, we only use it in asymmetric encryption, and the sender uses the recipient’s public key to encrypt the message.
- Fasten the technique by Using a single private key in symmetric encryption to encrypt and decrypt. Using two keys, a public key for encrypting and a private key for decryption, slows down the process.
- A single shared private key in symmetric encryption encrypts a huge amount of data. An asymmetric encryption technique uses a public key mechanism to encrypt small messages.
- We use a private key mechanism in symmetric encryption for securing the content of hard disk drives and other storage devices. We use the public key mechanism in asymmetric keys to secure web sessions, emails, online chats, etc.
Conclusion
So, public and private keys in cryptography are used to ensure the secrecy and authenticity of shared information. In a symmetric encryption technique, we use the same private key to encrypt as well as decrypt the message. However, in the asymmetric encryption technique, every participant has two keys, a public key available to all the participants, and the sender uses the recipient’s public key to encrypt the message. And the other key that each participant has is the private key; the recipient uses its private key to decrypt received messages.
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