Understanding Public Key and Private Key Encryption
By
Safeheron Team
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In the realm of encryption, the concepts of public keys and private keys are fundamental to asymmetric cryptography.
Public Key
- Definition: The public key is a cryptographic key that can be shared openly. It is used to encrypt data. Anyone who has access to the public key can use it to encrypt information that they want to send to the key owner.
- Usage Example: In a digital communication scenario, if Alice wants to send a confidential message to Bob, she can use Bob’s public key to encrypt the message. The public key is like a lock that anyone can use to lock a box. The encrypted message can then be sent over an insecure network such as the Internet.
Private Key
- Definition: The private key is the counterpart of the public key. It is kept secret by its owner. The private key is used to decrypt data that has been encrypted with the corresponding public key.
- Usage Example: Continuing with the previous example, when Bob receives the encrypted message from Alice, he uses his private key to decrypt it. The private key is like the key that can open the box locked with the public key. Only Bob, who has the private key, can access the original message.
How They Work Together
- The security of this system relies on the mathematical relationship between the public and private keys. It is computationally infeasible to derive the private key from the public key. This ensures that even if the public key is widely distributed, the private key remains secure.
- For example, in the RSA (Rivest – Shamir – Adleman) encryption algorithm, the key pair is generated based on large prime numbers. The encryption process involves complex mathematical operations using the public key, and the decryption process requires the corresponding private key to reverse these operations and retrieve the original plaintext message.
Applications
- Secure Communication: Widely used in protocols such as SSL/TLS for secure web browsing. When you visit a website using HTTPS, the server’s public key is used to encrypt the data sent from your browser to the server, and the server’s private key is used to decrypt it.
- Digital Signatures: The private key can also be used to create a digital signature. The owner signs a message with their private key, and others can verify the signature using the corresponding public key. This ensures the authenticity and integrity of the message.
