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Difference Between Public Key and Private Key in Cryptography

Difference Between Public Key and Private Key in Cryptography

Public keys and private keys are commonly used for encryption and decryption. Understanding the differences between them is not just about technical knowledge; it’s about knowing how smart systems keep our online world safe. In this blog, you’ll learn the basics of how we keep things secure on the internet while still being able to share what we want on the internet. 

Table of Contents

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Understanding Cryptography and the Basics of Encryption

Understanding Cryptography and the Basics of Encryption

Cryptography is like a digital security guard, making sure our online chats and information stay private and safe. It works by turning messages into a secret code that only the right person can understand. Imagine sending a secret note that only your friend can read. That’s what encryption does—it scrambles your message so no one else can read it. Decryption is like having the secret key to assemble the message and read it again. This whole process keeps our emails and online shopping safe.

Public Key and Private Key

There are two main key processes in cryptography: public key and private key. Think of the public key as a lock that anyone can close, but only the private key can open it. The private key is a secret key that only you have. It unlocks the scrambled messages. This two-key system is really strong; even if everyone knows your public key (the lock), only you with your private key can open it and see the message. This way, not only is your information kept safe, but it also makes sure that the people you’re talking to are really who they say they are. This is super important for things like keeping websites secure and making sure digital signatures are real in our online world.

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What is Public Key : Deep Dive into Public Key Infrastructure

Public Key is like a digital address that you share openly. It’s used in cryptography to receive secure messages or transactions. Think of it as your public email where others can send you encrypted messages, but only you, with your private key, can unlock and read them.

What is Private Key

Private key is like a secret password to your digital address (public key). It’s kept confidential and used to unlock encrypted messages or authorize secure transactions. Just like a key to your mailbox, it makes sure that only you can access and control what’s meant for you.

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Public Keys vs. Private Keys: What’s the Difference?

Differences Between Public Key and Private Key

Public keys are a business’s public address, available to everyone for encrypting messages. However, the private key is used to decrypt these messages. This fundamental difference supports the security in asymmetric encryption, ensuring secure communication. Let us find out the key difference between the public key and the private key.

AspectPublic KeyPrivate Key
Ownership and AccessibilityPublicly accessible to anyone and can be distributed openlyStrictly confidential and only accessible by the individual or entity it belongs to
Primary FunctionPrimarily used for encrypting data meant for the private key holder and verifying digital signaturesMainly used for decrypting data encrypted with the corresponding public key and signing digital documents
Algorithm Used The public key is used in algorithms such as RSA, DSS, etc.The private key is used in algorithms such as AES 128, AES 192, and AES 256. AES stands for Advanced Encryption Standard.
Distribution and SharingFreely shared and can be published in public directories or websites without compromising securityMust be kept secret and never shared to maintain security integrity
Security ConcernsRemains secure as long as the private key is kept confidentialHigh level of security is important. If compromised, it can lead to significant security breaches.
Pairing with Other KeyAlways paired with a corresponding private key, forming a unique key pairAlways paired with a corresponding public key in a cryptographic system
Role in Digital SignaturesVerifies digital signatures made with the corresponding private keyGenerates a digital signature that can be verified by anyone with the corresponding public key
Typical Use CasesEncrypting emails or documents, securing online transactions, and verifying identityDecrypting sensitive information, authenticating identity, and signing software or documents
Revocation and ReplacementCan be replaced or updated more easily than a private key without needing a new key pairIf compromised, it requires complete revocation and the generation of a new key pair.
Storage and ProtectionCan be stored in less secure, more accessible environmentsStored in highly secure environments, often with hardware support like HSMs (Hardware Security Modules)
Key Length and ComplexityLength and complexity are balanced between security needs and computational efficiency.Generally long and complex for security, matching the length of the public key
Example ScenarioA sender encrypts an email using the recipient’s public key to check only the recipient can read it.A user decrypts an encrypted email sent to them using their private key.

The above table breaks down the differences between public keys and private keys in a way that’s easy to understand. Knowing how these keys work is important, whether you’re sending emails, signing documents, or keeping your information safe online. 

Keep this guide as a handy reference to help you navigate the basics of digital security and cryptography, even if you’re just starting. It’s a simple yet powerful tool in your journey to understanding online safety and privacy.

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How to Generate a Public Key and a Private Key

There are various mathematical algorithms that secure digital communication. Among these, three stand out for their effectiveness and widespread use: RSA, DSS, and ECC.

  • Rivest-Shamir-Adleman (RSA): RSA algorithm is basic in this field. As the oldest method in public-private key cryptography, RSA is renowned for its use in transmitting shared keys for symmetric key cryptography. Its security is based on the computational difficulty of factoring large prime numbers, making it a trusted choice in various applications.
  • Digital Signature Standard (DSS): Developed under the guidance of the National Institute of Standards and Technology (NIST), DSS is a Federal Information Processing Standard. It primarily focuses on algorithms that generate digital signatures, ensuring the authenticity and integrity of digital documents.
  • Elliptic Curve Cryptography (ECC): ECC is known for its efficiency and strong security with shorter key lengths. It uses the properties of elliptic curves in generating keys and is widely employed for creating digital signatures and secure key agreements.

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To wrap it up, we’ve found out how public and private keys work in cryptography. Think of them as a team: the public key is like a mailbox anyone can drop a message into, and the private key is like the key that opens the mailbox, kept only by you. We’ve covered the basics of how they encrypt and decrypt data and why understanding this is key to keeping our online information safe.

If you’re just getting started in the world of digital security, keep exploring and asking questions. 

Why not try using these ideas in your own online activities? Feel free to share your experiences or ask questions in the comments and Intellipaat’s Community.

Frequently Asked Questions

What are public key and private key cryptography?

A public key is like a shared lock for messages, and a private key is the special key only one person has to unlock and read those messages. It’s like sending a secret letter—anyone can use the shared lock, but only you have the key to open and understand it. This keeps our digital talks safe and private, even if the path is not very secure.

How can you generate public and private keys on Linux?

In Linux, use the following commands with OpenSSL to generate public and private keys: Extract Public Key from Private Key: openssl rsa -pubout -in private_key.pem -out public_key.pem Generate Private Key: openssl genpkey -algorithm RSA -out private_key.pem These commands create a private key (`private_key.pem`) and get the corresponding public key (`public_key.pem`).

How can you create a public and private keys pair?

To create a public and private key pair, use a tool like OpenSSH or OpenSSL. Simply run a command, and it generates both keys. The public key is shared openly, while the private key remains secret. It’s like creating a lock (public key) and a unique key (private key) to secure your online communication.

What is an example of a public key?

An example of a public key is a digital address, such as someone’s email address. It’s shared openly, allowing others to send encrypted messages to that specific address. Just as you can share your email openly, a public key enables secure communication in the digital world.

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About the Author

Technical Lead - AWS Solutions Architect

Shivanshu is a Technical Lead and AWS Solutions Architect passionate about utilizing Cloud technology to empower businesses. Proficient in AWS, Terraform, and GCP, he crafts innovative solutions to propel companies forward. As an enthusiastic writer, he shares his expertise to inspire others in this field.