Public Key vs. Private Key Encryption: Key Differences Explained

This page compares Public Key Encryption vs Private Key Encryption, highlighting the core differences between them. There are two fundamental types of encryption: symmetric key and asymmetric key. Let’s dive in.

Symmetric Key Encryption

Symmetric key encryption employs the same key for both encryption and decryption. Think of it like a regular lock and key – the sender uses the key to lock (encrypt) the message, and the recipient uses the same key to unlock (decrypt) it.

Asymmetric Key Encryption (Public Key Encryption)

Asymmetric key encryption, on the other hand, uses different keys for encryption and decryption. This is often referred to as Public Key Encryption.

Figure 1: Public Key Encryption and Decryption System

Here’s a breakdown of how it works, referring to Figure 1:

• Encryption: The transmitting side converts plaintext into ciphertext (encrypted text) before sending it across the medium. Critically, it uses the public key of the intended recipient to encrypt the message. The recipient freely shares this public key.
• Decryption: The receiving side converts the encrypted text back into its original plaintext form. The receiver uses their private key to do this. The private key is generated and kept secret by the recipient.

The crucial point is that this is an asymmetric encryption type. The public key, which is transmitted openly, cannot be used to decrypt the message. Nor can it be used to derive the private key. The security relies on the mathematical relationship between the public and private keys, making it computationally infeasible to derive the private key from the public key.

Key Differences Summarized

In short, the main difference boils down to this:

• Symmetric Encryption: Single, shared secret key.
• Asymmetric (Public Key) Encryption: A pair of keys - a public key (shared) and a private key (kept secret).