Symmetric Key Algorithms
You already learned about symmetric key ciphers and the major issue with symmetric keys. Read the section in this article on symmetric key encryptions to learn more about the advantages and disadvantages of symmetric keys. There is more information about symmetric key ciphers in this article that will be covered in more detail later in this unit, but this article will give you a preview of 3DES, IDEA, and AES ciphers. View the flashcard tool as well to better understand and to learn the terms used in cryptography such as plaintext, ciphertext, key, encryption, decryption, countermeasure, symmetric key encryption, and block cipher.
4. Asymmetric Encryption
Unlike symmetric encryption methods, asymmetric encryption methods use two separate keys for the encryption and decryption process. Asymmetric encryption is also referred to as public key encryption. A public key is used during the encryption process to encrypt the plaintext message and a private key is used during the decryption process to decrypt ciphertext.
| Advantages | Disadvantages |
|---|---|
| Easier to deal with key distribution and ensure integrity of message | Slower due to multiple keys |
Watch the video, Encryption Part I: Introduction to Encryption 2 (6:23) which discusses asymmetric encryption and hashing.
If Alice wants to send a message that only Bob can read, Alice will use Bob's public key to encrypt the message. The only way the message can be decrypted is when Bob uses his private key.
Figure 2 – Asymmetric encryption
The most popular asymmetric algorithm is RSA which can provide key exchange, encryption, and digital signatures. The strength of this algorithm lies in the difficulty of calculating the prime factors of very large numbers. Other asymmetric algorithms include ElGamal, ECC, and Knapsack. Read the article, Asymmetric Encryption Algorithms, Diffie-Hellman, RSA, ECC, ElGamal, DSA, for a comparison of these algorithms.