Hop Integrity in the Internet introduces a new security defense, hop integrity, that can be used against denial-of-service attacks in the Internet. If a message that is part of a denial-of-service attack is originated by an adversarial host in the Internet and if the message header includes a wrong address for the originating host (in order to hide the true source of the attack), then the message will be classified as modified or replayed and will be discarded by the first router that receives the message in the Internet.

A suite of protocols for providing hop integrity in the Internet is discussed in great detail. In particular, each protocol in the suite is specified and verified using an abstract and formal notation called the Secure Protocol Notation. The protocols include:

- Secure address resolution

- Weak hop integrity

- Strong hop integrity using soft sequence numbers

- Strong hop integrity using hard sequence numbers

Other benefits of hop integrity extend to secure routing, mobile IP, and IP multicast.

There are two groups of researchers who are interested in designing network protocols and who cannot (yet) effectively communicate with one another c- cerning these protocols. The first is the group of protocol verifiers, and the second is the group of protocol implementors. The main reason for the lack of effective communication between these two groups is that these groups use languages with quite different semantics to specify network protocols. On one hand, the protocol verifiers use specification languages whose semantics are abstract, coarse-grained, and with large atom- ity. Clearly, protocol specifications that are developed based on such semantics are easier to prove correct. On the other hand, the protocol implementors use specification languages whose semantics are concrete, fine-grained, and with small atomicity. Protocol specifications that are developed based on such - mantics are easier to implement using system programming languages such as C, C++, and Java. To help in closing this communication gap between the group of protocol verifiers and the group of protocol implementors, we present in this monograph a protocol specification language called the Timed Abstract Protocol (or TAP, for short) notation. This notation is greatly influenced by the Abstract Protocol Notation in the textbook Elements of Network Protocol Design, written by the second author, Mohamed G. Gouda. The TAP notation has two types of sem- tics: an abstract semantics that appeals to the protocol verifiers and a concrete semantics thatappeals to the protocol implementors group.

Denial-of-service attacks are one of the most severe challenges confronting the online world. This ground-breaking volume discusses a new method of countering denial-of-service attacks called hop integrity. It details a suite of protocols for providing hop integrity. In particular, each protocol in this suite is specified and verified using an abstract and formal notation, called the Secure Protocol Notation. In addition, the book presents an alternative way to achieve strong hop integrity with hard sequence numbers.

There are two groups of researchers who are interested in designing network protocols and who cannot (yet) effectively communicate with one another c- cerning these protocols. The first is the group of protocol verifiers, and the second is the group of protocol implementors. The main reason for the lack of effective communication between these two groups is that these groups use languages with quite different semantics to specify network protocols. On one hand, the protocol verifiers use specification languages whose semantics are abstract, coarse-grained, and with large atom- ity. Clearly, protocol specifications that are developed based on such semantics are easier to prove correct. On the other hand, the protocol implementors use specification languages whose semantics are concrete, fine-grained, and with small atomicity. Protocol specifications that are developed based on such - mantics are easier to implement using system programming languages such as C, C++, and Java. To help in closing this communication gap between the group of protocol verifiers and the group of protocol implementors, we present in this monograph a protocol specification language called the Timed Abstract Protocol (or TAP, for short) notation. This notation is greatly influenced by the Abstract Protocol Notation in the textbook Elements of Network Protocol Design, written by the second author, Mohamed G. Gouda. The TAP notation has two types of sem- tics: an abstract semantics that appeals to the protocol verifiers and a concrete semantics thatappeals to the protocol implementors group.