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.

5. Perfect Forward Secrecy

If the public and private keys used in secure communications are compromised, the data exchanged in that session as well as previously exchanged data may be revealed. Perfect Forward Secrecy (PFS) ensures that a session key will not be compromised if a private key is compromised in the future. For example, IPsec negotiates new keys for every communication. Using IPsec, the compromise of a single key permits access to only the data protected by the single key.

The video, Twitter Toughens Security Against NSA Snooping (1:34), explains the implementation of forward secrecy on Twitter to encrypt its traffic on a session-by-session basis.