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Public Key Cryptography: Is It a Reliable Security Measure?

Public Key Cryptography: Is It a Reliable Security Measure?

 By Charles Joseph | Cybersecurity Researcher
 Published on August 1st, 2023
This post was updated on November 25th, 2023

Public Key Cryptography is a type of encryption that utilizes two keys – a private key and a public key. The private key is kept secret and secure, while the public key is shared openly, often over the internet. Whatever data is encrypted with one key can only be decrypted with the other key. This technique ensures secure communication and is commonly used in activities such as email encryption, secure browsing, and digital signatures.

Public Key Cryptography Examples

1. Email Encryption

To secure our online communication, we use a process like email encryption provided by Public Key Cryptography. This is all about transmitting sensitive or confidential information over the internet safely. When you wish to send a secure email, the body of the email is encrypted or locked using the recipient’s public key. This is done automatically by your email service if it supports encryption.

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Once the email is sent out on the internet, it can’t be unlocked or decrypted by anyone other than the recipient. That’s because the recipient is the only one who has access to the private key that pairs with the public key. Even if an interceptor gets a hold of the email during transit, the content remains unreadable without the correct private key. This keeps the content of the email secure and safe from prying eyes, ensuring that only the intended recipient can read it.

The beauty of this technology lies in its simplicity and its widespread use in securing our digital communications. It is emblematic of both the complexity and the accessibility of modern encryption methods.

2. Secure Websites (HTTPS)

If you’ve ever seen a website address beginning with “https”, that’s public key cryptography in action. The ‘s’ at the end of ‘http’ stands for secure, referring to a protocol for secure communication over a computer network which is widely used on the internet.

When you visit a secure website, any information you send over this site, such as credit card details or passwords, is encrypted using the website’s public key. This encryption process is handled in the background by the browser and the website’s server, ensuring any data that passes between them is unreadable to anyone else. This means even if someone manages to intercept the data, they will not be able to understand or use it without the corresponding private key.

The private key is kept secret and secure by the website owner, ensuring that only they can decrypt the data sent by visitors to their website. This provides a safe environment for users to share sensitive information, enhancing trust and confidence in online transactions.

3. Digital Signatures

Another application of public key cryptography is in digital signatures. Digital signatures play a crucial role in verifying the authenticity and integrity of digital messages and documents. When you digitally sign a document, you use your private key, which is kept secure and hidden.

The process involves creating a unique signature via encryption for the document using your private key. This signature is appended to the document, and it serves as a guarantee that the document is authentic and has not been tampered with.

Others can confirm the authenticity of this signature and, therefore, the document by using your freely available public key. If the signature matches, it confirms the document originated from you and was not manipulated in transit. This provides a high level of security for electronic documents, adding weight and legal standing in a manner similar to a handwritten signature.


Public Key Cryptography plays a vital role in ensuring secure communication and data transfer in our increasingly digital world. Whether it’s for email encryption, secure browsing, or verifying a digital signature, its strength lies in the fact that it allows us to transmit sensitive information over public networks with confidence, knowing that only the intended recipient can understand the data.

Key Takeaways

  • Public Key Cryptography is an encryption method that uses two keys – a private key (kept secret) and a public key (shared openly).
  • Email Encryption is one of the applications of public key cryptography where emails are secured using the recipient’s public key so that only the intended recipient can decrypt and read them.
  • Secure Websites or HTTPS uses public key cryptography to encrypt data passed between a browser and a website, offering safe online transactions.
  • Digital Signatures employ public key cryptography to authenticate that a digital document or message originates from a specific source.
  • Public key cryptography adds a layer of security in digital communications, ensuring the data’s confidentiality, origin integrity and even non-repudiation in the case of digital signatures.

Related Questions

1. What’s the difference between public key and private key in cryptography?

In public key cryptography, the public key is widely distributed and available to everyone, used for encrypting messages or verifying signatures. The private key is kept secret by its owner and is used for decrypting messages or creating digital signatures.

2. What is the importance of key pairs in Public Key Cryptography?

The key pair in public key cryptography is essential to secure communications. The public key is used to encrypt the message and the private key to decrypt it. This mechanism ensures only the intended recipient, who holds the private key, can read the message encrypted with their public key.

3. Is HTTPS completely secure?

HTTPS is much more secure than its unencrypted counterpart, HTTP, but it is not completely immune to threats. While it does make data in transit harder to intercept and read, it doesn’t guarantee the website you are communicating with is who they claim to be and it doesn’t protect the data once it reaches the server.

4. Can I hide my public key?

No, your public key is meant to be shared openly. It’s used to encrypt messages sent to you or verify your digital signature. The private key is the one that needs to be kept secret since it decrypts messages or creates digital signatures.

5. How are digital signatures created?

Digital signatures are created by taking a message, creating a message digest (small unique representation of original message) using a hashed algorithm, and then encrypting that digest with the sender’s private key. The encrypted digest forms the digital signature and is appended to the message before being sent.

"Amateurs hack systems, professionals hack people."
-- Bruce Schneier, a renown computer security professional
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