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Table of contents
Types of Public Key Cryptography
Public Key Encryption
Digital Signatures
Features of Public Key Cryptography
Applications of Public Key Cryptography
Hybrid Cryptosystems
Weakness of Public Key Cryptography
Symmetric Vs. Public Key Cryptography
Frequently Asked Questions
Which keys are required for public key cryptography?
Can communication be kept private with public key cryptography?
Which protocol makes use of public key encryption?
Which encryption algorithm is applied to public key systems?
What location should public keys be kept?
Last Updated: Mar 27, 2024

Introduction to Public Key Cryptography

Author Mayank Goyal
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The area of cryptographic systems that use pairs of related keys is known as public-key cryptography, also known as asymmetric cryptography. A public key and its accompanying private key make up each key pair. Cryptographic algorithms based on one-way functions are used to create key pairs. The private key must be kept hidden for public-key cryptography to be secure; nevertheless, security is not compromised if the public key is freely distributed.

public key cryptography

Types of Public Key Cryptography

Two of the best-known use cases of public key cryptography are

  • Public Key Encryption
  • Digital Signature.
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Public Key Encryption

Encryption describes the process of converting plaintext into ciphertext. The algorithm and key are the two components of the encryption process. 

Asymmetric cryptography, or public key encryption, uses two sets of keys for encryption and decryption. A public key is known to everyone, and a private key (Secret key)

public key encryption

A pair of keys named public and private keys are connected to an entity in public-key encryption. Each public key is made available, while the associated private key is kept private. Only the appropriate private key can be used to decrypt data that has been encrypted using a public key.

Public keys can be freely circulated under the "Public-Key Encryption" technique mentioned above, but only authorized individuals can read data that has been encrypted using this key. In most cases, sending encrypted data involves encrypting it using the recipient's public key and decrypting it with their corresponding private key.

Public-key encryption needs more processing than symmetric-key encryption and may not be practical for encrypting and decrypting huge volumes of data. However, delivering a symmetric key via public-key encryption is feasible so extra data can be encrypted later. The SSL/TLS protocols follow this strategy.

Digital Signatures

The reverse process of public key encryption is digital signatures. Only the associated public key can be used to decrypt data that has been encrypted with a private key. But since anyone with the public key, which is by definition released, might decrypt the material, it is generally not advised to use this method to encrypt sensitive data. 

digital signatures

However, private-key encryption is advantageous because it enables the use of the private key for digital signatures, a crucial prerequisite for electronic commerce and other business applications of cryptography. The message can then be used by client software, such as Mozilla Firefox, to verify that it was signed with the correct private key and that it hasn't been tampered with since being signed.

Features of Public Key Cryptography

  • Data sent between two communicating parties can be hidden via encryption and decryption. Before sending the data, the sender scrambles or encrypts it. After receiving the data, the receiver decrypts or unscrambles it. An outsider cannot decipher the encrypted data while it is en route.
  • Nonrepudiation is the ability to communicate data without fear of the sender later asserting that it was never sent, preventing alterations to the data.

Applications of Public Key Cryptography

  • A public key encryption system's most obvious use is for encrypting communication to provide confidentiality. To do this, a sender uses the recipient's public key to encrypt a message, which the recipient's paired private key can only decrypt.
  • The use of digital signatures in public key cryptography is another. Schemes for digital signatures can be used to verify the sender.
  • Digital signatures are used in non-repudiation systems to ensure that one party cannot successfully contest the authorship of a communication or document.
  • Digital currency, password-authenticated key agreements, time-stamping services, and non-repudiation protocols are additional applications built on this foundation.

Hybrid Cryptosystems

It is typical to use a public/private asymmetric key-exchange algorithm to encrypt and exchange a symmetric key. It is then used by symmetric-key cryptography to transmit data using the now-shared symmetric key for a symmetric key encryption algorithm because asymmetric key algorithms are almost always much more computationally intensive than symmetric ones. These methods are used by PGP, SSH, and the SSL/TLS family of schemes, which is why they are referred to be hybrid cryptosystems.

Weakness of Public Key Cryptography

  • Due to their uniqueness, public-key cryptography keys are more computationally expensive than their equivalents in symmetric cryptography.
  • Asymmetric keys must be significantly longer than symmetric-cryptography keys to boast equal security.
  • Asymmetric cryptography's keys are more susceptible to brute force assaults than symmetric cryptography's keys are. 
  • Public-key cryptography has methods that make private keys easier to decrypt than a brute-force approach. The widely used and ground-breaking RSA algorithm contains an algorithm that makes it vulnerable to attacks in less time than it would take to employ brute force. 
  • In other algorithms, producing larger keys will typically prevent a brute force assault from being successful for any appreciable amount of time, although these computations become more computationally costly.
  • Depending on the amount of processing power an attacker has, these longer keys can still have varying degrees of usefulness.
  • In addition, public-key cryptography is susceptible to man-in-the-middle attacks. In this case, an evil third party intercepts a public key traveling to one of the parties. The third party can then send a message pretending to be from the original sender while also including their public key. This method allows an attacker to effectively mimic each party to a discussion at every stage of the exchange without the knowledge of the other participants.

Symmetric Vs. Public Key Cryptography

Symmetric Key Cryptography Public Key Cryptography
It is also known as a private key. It is also known as an asymmetric key.
Only one key is used, which is the private key. Two keys are used. One is public, and the other is the private key.
The Key is kept secret. One key is publically available; the other is kept secret.
The same keys are used for encryption and decryption. Different keys are used for encryption and decryption.
Faster than public key cryptography. Slower than symmetric key cryptography.
It can be used for both small and long message encryption. It is used only for small messages.

Frequently Asked Questions

Which keys are required for public key cryptography?

A public key pair is used in public key cryptography and is associated with an entity that must authenticate its identity, sign, or encrypt material digitally. Each private key is kept hidden while the corresponding public key is made public.

Can communication be kept private with public key cryptography?

Public-key encryption doesn't reveal to the recipient who sent a message; rather, it only encrypts the message's content into a ciphertext that can only be deciphered with the private key.

Which protocol makes use of public key encryption?

Public key cryptography is frequently used for digital signatures, email traffic encryption using S/MIME, and other cryptographic protocols, including SSL/TLS, SSH, and HTTPS.

Which encryption algorithm is applied to public key systems?

The current public key algorithms are Rivest-Shamir-Adleman (RSA), Elliptic Curve Digital Signature Algorithm (ECDSA), and digital signatures algorithm(DSA).

What location should public keys be kept?

Data is securely encrypted before being delivered over the internet using the public key, which is normally kept on a server for the public key infrastructure.


This article taught us the major differences between public and symmetric key cryptography. Later, we looked into each of the uses of public key cryptography. Lastly, we learned about the applications and weaknesses of public key cryptography.

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