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.

9. Key Stretching

Key stretching, or key strengthening, uses cryptography to make a weak key stronger by increasing the time that it takes to test each possible key. An algorithm is applied to the original key to produce an enhanced key. Key stretching provides a key of at least 128 bits.

Key stretching slows down an attacker because the attacker has to compute the stretching function for every guess in the attack. PGP, WPA, and WPA2 all use key stretching.