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RSA chia sẻ nhiều điểm tương đồng với thuật toán DH trong đó RSA cũng dựa trên các số nguyên nhân và bao thanh toán lớn. Tuy nhiên, RSA là nhanh hơn đáng kể hơn so với DH, dẫn đến một sự chia rẽ trong lĩnh vực mật mã không đối xứng đề cập đến DH và các thuật toán tương tự như hệ thống phân phối khóa công cộng (PKDS) | Cisco Network Security Chapter 7 775 RSA RSA shares many similarities with the DH algorithm in that RSA is also based on multiplying and factoring large integers. However RSA is significantly faster than DH leading to a split in the asymmetric cryptography field that refers to DH and similar algorithms as Public Key Distribution Systems PKDS and RSA and similar algorithms as PKE. PKDS systems are used as session-key exchange mechanisms while PKE systems are generally considered fast enough to encrypt reasonably small messages. However PKE systems like RSA are not considered fast enough to encrypt large amounts of data such as entire file systems or high-speed communications lines. RSA DH and other asymmetric algorithms use much larger keys than their symmetric counterparts. Common key sizes include 1024 bits and 2048 bits the keys need to be this large because factoring while still a difficult operation is much easier to perform than the exhaustive key search approach used with symmetric algorithms. The RSA algorithm has been in the public domain since RSA Security placed it there two weeks before the patent expired in September 2000. It is now freely available for use by anyone for any purpose. It commonly used in applications such as PGP and SSH. In fact you can download a freeware version of PGP from products pgp versions freeware if you want to experiment and learn more about PKE. Skeme and Oakley Protocols The Oakley protocol describes a series of key exchanges called modes and details the services provided by each for example perfect forward secrecy for keys identity protection and authentication . The Skeme protocol describes a versatile key exchange technique that provides anonymity reputability and quick key refreshment. Their relationship to Internet Security Association and Key Management Protocol ISAKMP is fairly straightforward where Oakley defines modes of exchange ISAKMP defines phases of when each is applied. IPsec Concepts The security