What is Public Key Cryptography?

Asymmetric cryptography or public key cryptography is where 2 keys are used to establish a secure connection between 2 entities in a network. Public key cryptography utilizes asymmetric encryption. The private key is kept only with the owner of the website, the server, or with whom you want to communicate. The public key is distributed among the clients and the userbase. The private key can only decrypt the data encrypted using the public key. Asymmetric cryptography thus protects against Man in the Middle attacks and attacks where the data-in-transit might be compromised or modified.

Functions of Public-key cryptography

The major functions of public-key cryptography are encryption, decryption, digital signatures, and key exchange.

Encryption

Public-key cryptography facilitates the encryption of messages or data to ensure secure communication over untrusted networks.The recipient’s public key is used for encryption, and only the corresponding private key can decrypt the message. This process ensures that only the intended recipient can decipher the information.

Decryption

Decryption is the process of reverting encrypted data back to its original form, and public-key cryptography allows this process securely.The recipient uses their private key to decrypt messages that were encrypted with their corresponding public key. This ensures that only the authorized recipient can access the original information.

Digital Signatures

Public-key cryptography enables the creation and verification of digital signatures to authenticate the origin and integrity of messages or documents. The sender signs the message with their private key, and the recipient can verify the signature using the sender’s public key. This process ensures that the message has not been tampered with and was indeed sent by the claimed sender.

Key Exchange

Public-key cryptography facilitates secure exchange between parties to establish shared secret keys for symmetric encryption. Parties can exchange public keys and derive a shared secret key without exposing their private keys. This shared key is then used for symmetric encryption, enhancing the security of subsequent communication.

A high-level real-world example of public-key cryptography is the secure transmission of information over the internet, particularly during online transactions, like shopping or banking.

Example of public-key cryptography

Imagine you are making an online purchase:

Encryption (Sender – User’s Browser):

The user’s browser (sender) has the public key of the website. Before transmitting sensitive information (e.g., credit card details), the browser uses the website’s public key to encrypt the data.

Transmission:

The encrypted data (cipher text) is sent over the internet to the website.

Decryption (Recipient – Website):

The website (recipient), which possesses the corresponding private key, decrypts the received information. Only the website, with the private key, can successfully decrypt and access the transmitted data.

Advantages

• Authentication Assurance

  Public key cryptography strengthens authentication by enabling the verification of message authenticity through digital signatures. This ensures that recipients can confidently validate the origin of messages, enhancing the overall security of communication channels.

• Simplified Key Distribution

  Public key cryptography addresses the complexities of key distribution by encouraging users to openly share their public keys. This eliminates the need for secure pre-shared key channels, offering a more convenient and scalable approach to managing encryption keys.

• Non-Repudiation via Digital Signatures

  Public key cryptography introduces non-repudiation features comparable to physical signatures. Messages digitally signed serve as unequivocal acknowledgments, preventing senders from disowning their communications. This strengthens the accountability and trustworthiness of digital interactions.

Disadvantages

• Security Risks of Private Key Exposure

  If an attacker gains access to your private key, there is a significant security risk as they can decrypt and read all your messages. The confidentiality of your communication becomes compromised, emphasizing the importance of safeguarding private keys.

• Impact of Private Key Loss

  The loss of a private key poses a critical challenge, as it renders you unable to decrypt received messages. This loss of access can result in the permanent inability to retrieve or understand sensitive information, underscoring the need for secure key management practices.

• Performance Considerations

  Public key cryptography tends to operate at a slower pace compared to symmetric cryptography. This method may not be suitable for decrypting bulk messages efficiently, highlighting a potential drawback in terms of speed and performance, particularly in scenarios where large volumes of data need decryption.

Conclusion

In conclusion, public key cryptography is a fundamental technology that underpins the security of digital communication in our interconnected world. Its ability to provide secure encryption, digital signatures, and key exchange mechanisms has made it indispensable for securing online transactions, authenticating users, and ensuring data integrity. As cyber threats continue to evolve, public key cryptography remains a powerful tool in safeguarding sensitive information and fostering trust in the digital realm.