| 6.2 |  | IOS Cryptosystem |
| 6.2.1 |  | Overview |

| The IOS cryptosystem can perform three primary tasks, which include encryption, authentication, and key management. The two methods to provide encryption are symmetric and asymmetric. Symmetric, or secret key, encryption includes Data Encryption Standard (DES), Triple Data Encryption Standard (3DES), and Advanced Encryption Standard (AES). Asymmetric, or public key, encryption includes the Rivest, Shamir and Adleman (RSA) algorithm. These will be discussed in detail in the next section.

There are several technologies that provide authentication. They include Message Authentication Code (MAC), Hashed Message Authentication Code (HMAC), and digital signatures. MD5 and Secure Hash Algorithm (SHA) are hash functions that help provide authentication.

Many standards have emerged to protect the secrecy of keys, and to facilitate the changing of these keys. The three methods of key management include manual, secret key exchange, and public key exchange. The Diffie-Hellman method implements key exchange without exchanging the actual keys. This is the most well-known and widely used algorithm for establishing session keys to encrypt data.