What is the difference between symmetric and asymmetric encryption?

Symmetric Encryption

The same key is used for both encryption and decryption.

Key Characteristic: Single shared secret key.

Example Algorithms:
AES (Advanced Encryption Standard), DES (Data Encryption Standard), 3DES, Blowfish.

How it works:

• The sender encrypts the plaintext using a secret key.
• The receiver uses the same key to decrypt the ciphertext.

Advantages:

• Much faster and less computationally intensive.
• Suitable for encrypting large amounts of data (e.g., files, disks).

Disadvantages:

• Key distribution problem: both parties must securely share the same key.
• If the key is compromised, all communications encrypted with it are insecure.

Asymmetric Encryption

Uses a pair of keys — a public key and a private key.

Key Characteristic:

• Public key: Used for encryption (shared openly).
• Private key: Used for decryption (kept secret).

Example Algorithms:
RSA, DSA, ECC (Elliptic Curve Cryptography).

How it works:

• The sender encrypts the message using the recipient’s public key.
• Only the recipient can decrypt it using their private key.

Advantages:

• No need to share secret keys securely beforehand.
• Enables digital signatures and authentication.

Disadvantages:

• Slower than symmetric encryption.
• Not ideal for large data encryption (usually used to exchange symmetric keys instead).

Typical Real-World Usage

In practice, both are often used together:

• Asymmetric encryption (e.g., RSA) is used to securely exchange a symmetric key.
• Symmetric encryption (e.g., AES) then encrypts the actual data efficiently.
• This hybrid approach is used in protocols like HTTPS, SSL/TLS, and PGP.

Summary Table