Public Key: How Secure Can It Be?

Public Key: How Secure Can It Be?

 By Charles Joseph | Cybersecurity Advocate
 Last update: November 25, 2023

A Public Key is a form of digital code that is available to everyone. It is one half of a pair of cryptographic keys used in various internet protocols. When combined with its corresponding private key, secure online data communication can be achieved, whether it be through emails, websites, or other forms of online transactions. A public key turns data into a scrambled version that can only be decoded using the correct private key.

Public Key Examples

1. Email Encryption

In the realm of email communication, public keys play a crucial role in ensuring the secure transmission of data. Let’s take a look at the scenario involving two individuals, John and Jane. Suppose John wants to send an encrypted email to Jane. To secure this email, he uses Jane’s public key, which is accessible to everyone, to encrypt the message.

At this stage, the email becomes a series of random characters and symbols, incomprehensible to anyone intercepting the communication. Now, the unique aspect here is that only Jane, the intended recipient, has the corresponding private key capable of decoding this secured message.

So, when Jane receives this email, she uses her private key to decrypt the message and read it. Throughout this process, the data remains safe from potential cyber threats, thanks to the use of public and private keys in encryption.

2. Website Security

Public keys also facilitate secure online browsing and transactions, a crucial aspect in today’s digital era. Here’s a practical illustration. When you decide to visit a website that values security, often indicated by an ‘https’ in front of the website URL, the first action that takes place is the exchange of keys between your computer (the client) and the website (the server).

Stay One Step Ahead of Cyber Threats

Want to Be the Smartest Guy in the Room? Get the Latest Cybersecurity News and Insights.
We respect your privacy and you can unsubscribe anytime.

The website shares its public key with your client machine. This key will be used to encrypt sensitive information you intend to share with the website, such as login credentials or financial details. Now, the data you send to the website is in an encrypted form, a mix of random characters that wouldn’t make sense to any would-be interceptors.

The website, on the other hand, has access to the unique private key that can decrypt this data. It uses this private key to decode the information you’ve sent, making sure the process is secure from end to end. This way, public keys help in establishing secure connections with websites, protecting your data against potential threats.

3. Digital Signatures

Digital signatures are another practical application of public keys. They are used to verify the authenticity and integrity of a document or a message. Let’s consider a situation where Alice wants to digitally sign a document.

Alice will first use her private key to generate a digital signature. This digital signature is essentially a mathematical code generated using the contents of the document and Alice’s private key. The signature serves as a unique identifier that associates the document with Alice.

When another person like Bob, wants to confirm that Alice is indeed the author of the document, he will use Alice’s public key. Since public keys are open to everyone, Bob can easily access Alice’s. He uses this public key along with the digital signature to validate the document. If it verifies, it confirms that the document has not been tampered with and it indeed belongs to Alice. Hence, the use of public keys in digital signatures effectively authenticates the source and secures the data.


Public keys form an integral part of modern cybersecurity practices. They serve invaluable roles, from securing emails and website interactions to legitimizing digital signatures, thus playing a vital role in safeguarding digital communication against potential threats.

Key Takeaways

  • Public keys are crucial for secure online communication. They encrypt information so that only the person with the correct corresponding private key can decipher it.
  • Email Encryption: using public keys, confidential emails can be sent safely; the receiver uses their private key to decrypt the received message.
  • Website Security: Public keys aid in securing website interactions, encrypting the data sent from the client to the server.
  • Digital signatures use public keys to confirm the authenticity and integrity of a document or a message.

Related Questions

1. What happens if a public key is lost?

If a public key is lost, it’s not a big issue because public keys are meant to be shared publicly. They can be reissued or restored from wherever they were stored or published.

2. Is it possible to derive a private key from a public key?

No, it’s computationally unfeasible to derive a private key from a public key. The security of public key cryptography hinges on this fact.

3. Can two people have the same public key?

No, each pair of keys is unique. If two people had the same public key, they would also have the same private key, which could lead to security concerns.

4. How is authenticity retained in digital signatures?

The authenticity in digital signatures is retained by the usage of the sender’s private key to create the signature, and the sender’s public key being used by the recipient to validate the signature.

5. Can someone send encrypted data using my public key?

Yes, anyone who has your public key can send you an encrypted message. However, only you, with your private key, would be able to decrypt and read it.

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