Public Key Cryptography: Decoding the Basics

Public Key Cryptography

Are you puzzled by public and private keys? You’re in the right place! Here’s your handy guide to understanding these crucial components of Public Key Cryptography.

We’ll show how they work, where they’re used, and why they’re essential for safe communication. You’ll learn the difference between public key and private key and how they enhance security in technologies you use daily.

So, let’s explore public and private key encryption together.

Table of Contents

  1. What Is Public Key Cryptography?
  2. How Does TLS/SSL Use Public Key Cryptography?
  3. What Is Public Key Encryption and How Does It Work?
  4. What Is Private Key Encryption and How Does It Work?
  5. What Is the Difference Between a Public Key and a Private Key?
  6. What Are Some Examples of Public Key and Private Key Encryption Uses?

What Is Public Key Cryptography?

Public Key Cryptography (PKC) forms the backbone of various secure communication protocols, including Secure Sockets Layer (SSL), Transport Layer Security (TLS), and many others.

At its core, PKC is an asymmetric encryption system. That means it uses two different keys for encryption and decryption. You’ve got a public key that you can freely distribute and a private key that you must keep secret. Anyone can use your public key to encrypt a message, but only you, with your private key, can decrypt it.

How Does Public and Private Key Encryption Work?

Now, let’s go a little further. When someone wants to send you a secure message, they’ll encrypt it using your public key, creating a ciphertext that only the private key possessor can decrypt. This way, even if someone intercepts the message, without your private key, they can’t decipher it.

It’s not just for encrypting messages, though. You can flip the process for digital signatures – a way to ensure a message hasn’t been tampered with. You’d use your private key to encrypt the message or a hashed version. Then, anyone can verify its authenticity by decrypting the signature with your public key.

Managing keys can be complex, and there’s the risk that if your private key is lost or stolen, your security is compromised. Therefore, it’s crucial to handle your keys with care.

How Does TLS/SSL Use Public Key Cryptography?

Now that you know how PKC works, let’s see how protocols like TLS/SSL apply this method for secure transmission. TLS/SSL, or Transport Layer Security and its predecessor, Secure Sockets Layer, are cryptographic protocols designed to provide secure communication over a computer network. They utilize public key encryption, specifically asymmetric cryptography, to achieve this. SSL is now deprecated, with TLS being the standard.

When a client connects to a server secured with TLS, the server shares its public key with the client to establish an encrypted connection using digital certificates that contain the public key and the server’s identity. The client uses this public key to encrypt and send a secret key back to the server.

Here’s where the private key for the SSL certificate comes into play. The server uses its private key to decrypt the secret key sent by the client. This key pair – public and private keys – are uniquely related. Anything encrypted with the public key can only be decrypted by the corresponding private key.

Once the secret key is decrypted, both the server and the client have a shared secret key. This key is then used for symmetric encryption of the data sent between them during that session.

In essence, TLS/SSL uses asymmetric cryptography for the initial handshake to securely establish a symmetric key. This symmetric key is then used for the bulk encryption of data. This combination of asymmetric and symmetric encryption ensures secure, efficient communication.

What Is Public Key Encryption and How Does It Work?

Now that you’ve got a good grip on how TLS/SSL uses private and public keys, let’s look at public key encryption.

Public key encryption, also known as asymmetric encryption, is a method of encrypting data using a pair of keys.

Here’s how public encryption works: The public key encrypts sensitive data, and anyone can use it to encode information. On the other hand, the private key is secret and is only known to the owner. This private key decrypts the data encrypted with the corresponding public key.

For example, if Alice wants to send sensitive information to Bob, she’ll encrypt it using Bob’s public key. Bob will then use his private key to decrypt the received data. Even if someone intercepts the information, they won’t be able to read it without Bob’s matching private key.

Public key encryption uses a process called key pair generation. Both keys are mathematically linked – what one key encrypts, only the other can decrypt.

Public key encryption secures communication over the Internet, including email messages and online banking transactions. The most common public key encryption algorithms include RSA (Rivest-Shamir-Adleman) and ECC (Elliptic Curve Cryptography).

What Is Private Key Encryption and How Does It Work?

Private key encryption is a different process compared to public key encryption. This method involves only one key used for both encryption and decryption.

In private key encryption, also known as symmetric cryptography, you’ll use the same key to encrypt and decrypt the data. It’s like locking and unlocking a personal safe with the same key. Here’s how it works: let’s say you’ve got a message that needs to be encrypted. You’ll apply the private key to this plaintext using an encryption algorithm to transform it into an unreadable format called ciphertext.

This ciphertext can only be decrypted back into the plaintext using the same private key. Any third party without the private key won’t be able to decipher the message, ensuring it remains confidential.

However, the challenge lies in securely sharing the private key among users. If intercepted, an unauthorized third party could decrypt any encrypted messages. As such, private key encryption is mainly employed in secure environments where key distribution isn’t an issue.

What Is the Difference Between a Public Key and a Private Key?

You might be wondering what distinguishes a public key from a private key.

As you already know, the public key is used for encryption and is freely shared, while the private key, which is kept secure and confidential, is utilized for decryption. Let’s explore other differences between private key vs public key cryptography.

Private Keys Security

The security of your private key is paramount as it’s the only means you have to decrypt messages encrypted with your public key. Private keys are long strings of numbers and letters from a mathematical algorithm. They’re unique and impossible to replicate.

In contrast, a public key is derived from a private key and can be shared openly. Even though you can figure out a private key from a public key, it’s practically impossible because it would take a long time with today’s computers. So, keep your private keys safe and hidden from anyone who tries to snoop around.

If someone gains access to your private keys, they effectively control your encrypted data. It’s crucial to understand this distinction for maintaining robust security protocols.

Various Public Key and Private key Differences Emphasized

While both keys are integral to encryption, several crucial differences set public and private keys apart.

In symmetric key cryptography, the same key is used for encryption and decryption. However, with public and private keys, two keys are involved.

The public key is like a front door, open for anyone to encrypt messages, while the private key is the trusted courier, only you hold for decryption.

The decryption process requires checking if the received message matches the digital signature standard. If the signature matches, only the intended recipient can decrypt it.

With prime factorization, the private key becomes a secret key, and with elliptic curve cryptography, it can generate digital signatures.

A key agreement leads to a shared secret key, ensuring only encrypted messages according to federal information processing standards are valid.

What Are Some Examples of Public Key and Private Key Encryption Uses?

Let’s consider three primary examples: secure email communications, cryptocurrency transactions, and website authentication.

Secure Email Communications

In securing your email communications, two primary uses of public key and private key encryption come into action.

Firstly, these keys ensure confidentiality. When you’re sending an email, it’s encrypted with the recipient’s public key and only one private key can decrypt it. If a hacker intercepts the email, they can’t read it without the corresponding private key.

Secondly, the keys provide authentication and non-repudiation. When you sign an email with your private key, the recipient can use your public key to verify it was indeed you who sent it. Moreover, you can’t deny sending the email since only you have access to your private key.

These encryption methods secure email messages, protecting sensitive information from unauthorized access and tampering.

Website Authentication

The site’s server generates a pair of keys: one private, kept secret, and one public, shared with your browser. Your browser then encrypts your password using this public key. Only the server, with its private key, can decrypt and verify your password.

Another public key encryption example is TLS, used to secure data transmission between a browser and a website. The site’s SSL certificate contains a public key. Your browser uses this key to encrypt data sent to the site, which only the site’s private key can decrypt, ensuring data privacy and integrity.

Cryptocurrency Transactions

In this digital economy, your public key is akin to your bank account number. It’s an address to which others can send cryptocurrency. However, the private key is like your secret PIN or password, allowing you to access and manage your funds.

For instance, when you transact in Bitcoin, you sign the transaction with your private key, which is then publicly verified using your public key. This cryptographic signature proves you’re the rightful owner of the funds.


Is Public Key Encryption Asymmetric or Symmetric?

Public Key Encryption is asymmetric because it uses key pairs. The public key is shared openly, allowing anyone to encrypt messages, while the private key is kept secret and is used for decryption.

What Is Another Name for Public Key Encryption?

Another name for Public Key Encryption is Asymmetric Encryption, as it involves a pair of keys, one for encryption (public key) and another for decryption (private key), providing a distinct approach from symmetric encryption where the same key is used for both encryption and decryption

Is Public Key Encryption Secure?

Yes, Public Key Encryption is considered secure due to its use of a pair of keys, with the private key kept confidential. The security relies on the difficulty of deriving the private key from the public

Is the Public Key a Number?

The public key is a large number that results from complex mathematical operations. Specifically, it is derived from mathematical algorithms involving prime numbers, making it challenging to reverse-engineer the private key from the public key.

Where Is the Private Key Stored?

The private key is stored securely on the owner’s device, on the server, or in a designated key management system.

Can I Share My Public Key?

Yes, sharing your public key is a standard and secure practice. Your public key is designed for distribution and allows others to encrypt messages or verify digital signatures associated with your private key.

How are Public and Private Keys Generated?

Public and private keys are generated using mathematical algorithms, often involving complex operations with prime numbers. The public key is derived from the private key, and both are generated together as a pair to ensure their mathematical relationship.


In summary, understanding public vs private key cryptography is all about recognizing the difference between public and private keys. The public key encrypts, while the private key decrypts information.

In the dynamic online security space, the practical implications of the public and private keys are everywhere. PKC powers secure web browsing and file transfers. It protects blockchain transactions and email communication. Remember, store your private keys in a safe location, and your sensitive data won’t fall into attackers’ hands.

Save 10% on SSL Certificates when ordering today!

Fast issuance, strong encryption, 99.99% browser trust, dedicated support, and 25-day money-back guarantee. Coupon code: SAVE10

Written by

Experienced content writer specializing in SSL Certificates. Transforming intricate cybersecurity topics into clear, engaging content. Contribute to improving digital security through impactful narratives.