Two blue armies are each poised on opposite hills preparing to attack a single red army in the valley. The red army can defeat either of the blue armies separately but will fail to defeat both blue armies if they attack simultaneously. The blue armies communicate via an unreliable communications system (a foot soldier). The commander with one of the blue armies would like to attack at noon. His problem is this: If he sends a message to the other blue army, ordering the attack, he cannot be sure it will get through. He could ask for acknowledgment, but that might not get through. Is there a protocol that the two blue armies can use to avoid defeat?

Two blue armies are each poised on opposite hills preparing to attack a single red army in the valley. The red army can defeat either of the blue armies separately but will fail to defeat both blue armies if they attack simultaneously. The blue armies communicate via an unreliable communications system (a foot soldier). The commander with one of the blue armies would like to attack at noon. His problem is this: If he sends a message to the other blue army, ordering the attack, he cannot be sure it will get through. He could ask for acknowledgment, but that might not get through. Is there a protocol that the two blue armies can use to avoid defeat?

Database System Concepts

7th Edition

ISBN:9780078022159

Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Chapter1: Introduction

Section: Chapter Questions

Problem 1PE

See similar textbooks

Similar questions

Prior to the introduction of IEEE 802.11i, the security scheme for IEEE 802.11 was Wired Equivalent Privacy (WEP). WEP assumed all devices in the network share a secret key. The purpose of the authentication scenario is for the STA to prove that it possesses the secret key. Authentication proceeds as shown in Figure 24.13 . The STA sends a message to the AP requesting authentication. The AP issues a challenge, which is a sequence of 128 random bytes, sent as plaintext. The STA encrypts the challenge with the shared key and returns it to the AP. The AP decrypts the incoming value and compares it to the challenge that it sent. If there is a match, the AP confirms that authentication has succeeded.
Design a cryptographic solution for implementing the dinning cryptographers protocol. You should consider the following: The secret messages shared between any two agents in the protocol are communicated over public channels only. The announcements made by each agent must be traceable in a trustworthy way to that agent. Your solution should be a new protocol that addresses the above two requirements.
A group of individuals are living on an island when a visitor arrives with an unusual order: all blue-eyed people must leave the island immediately. Every evening at 8:00 p.m., a flight will depart. Everyone can see everyone else's eye colour, but no one knows their own (nor is anyone allowed to tell them). Furthermore, they have no idea how many people have blue eyes, but they do know that at least one person has. How long will it take for the blue-eyed individuals to leave?
A code must have certain properties in order that any errors can be corrected. Let CC Z be the code C = {23410, 34102, 44113, 21110, 01103}. Which of these scenarios shows that C is not 1-error correcting? O If 44113 is sent and an error changes the second digit 4 to 1, the receiver cannot know what error has occurred. O If the receiver gets the word 00000, they cannot know what message was sent. O If 23410 is sent and an error change the 3rd digit to 1, the receiver cannot know what error has occurred. O If 23410 is sent and an error moves the first digit 2 to the last place, making 34102, the receiver cannot know that any error has occurred
The message validation server is able to validate two types of messages - type A and type B messages correspondingly. It is commonly believed that the validation time of type B message is somewhat longer than the validation of type A message. Additionally, it's commonly believed that the actual validation time depends largely only on the type of messages (A and B types) and doesn't depend in an essential amount on the message content. However, nobody hasn't checked these claims in practice. We have reliable statistics for four different sessions: • 1st session - 17,648 of type A messages and 11,414 type B messages were validated, session lasted 6 minutes and 7.90 seconds. . 2nd session - 6836 of type A messages and 12,618 type B messages were validated, session lasted 4 minutes and 23.80 seconds. • 3rd session - 24,616 of type A messages and 17,648 type B messages were validated, session lasted 8 minutes and 56.10 seconds. . 4th session - 10,684 of type A messages and 12,684 type B…
A messaging system reads message as 4-digit positive integer d1d2d3d4 and stores encoding of the message e1e2e3e4 for security reason. The encoding process is as follows: ei = (di+i) mod 3 For example, if message is 4590, the encoded message is 2101. Read any arbitrary message and display the encoded message in the following format: Original message = Encoded message = language : C
We have intercepted a message that we need to decode. Luckily, we know that they use the letters A to Z, space, 0 to 9. We also know that when they encode messages they start by shifting the first letter once to the left, then shift the next twvo letters right twice, then the next three letters left 3 times, then the next four letters right 4 times, the next five letters left 5 times, and so on. a. If the message intercepted was HMMG2WEIAO what was the original message? b. What would we get if we encoded the phrase 2750H FRSC (the Os are zeros) using the given algorithm?
Consider the following scenario: The ABC Bank has many ATM branches all over the country. The customers of the bank use these machines mainly for withdrawing money. Further they can transfer money from one account to another using these machines. Also they can deposit any amount of money into their accounts. The customers can contact a banking assistant through the system if any error occurred during a transaction. The ATM can be filled only by cashier. The system should authenticate the users before they are allowed to use it for the transactions mentioned above. Draw use case diagram for the above scenario Can I have a step-by-step explanation on drawing the use case diagram with the completed use case diagram? Thank you!
Computer science Use C language to solve the question. The initial server and client .c code is given write code using these .c client and server files. Q1: Design a client-server model for two-way communication. Both the client and server should beable to send and receive messages.Upon the establishment of successful connection, the server should send a message, “Hi, youhave connected to the server!”.[The client should then send a string to the server. The server should reverse the string andsend it back to the client. The client should then display the received string.] This job will bedone in a loop of 5 times. -------------------------------------------- server.c #include <stdio.h> #include <stdlib.h> #include <sys/socket.h> #include <sys/types.h> #include <netinet/in.h> int main() { char server_message[256] = "Hi, Yes you have reached the server!"; char buf[200]; // create the server socket int server_socket; server_socket = socket(AF_INET,…
Major Luna is sending military troops from his base (A) to the town of G. However, there is no direct route between A and G. Instead, the troops must pass through other places, namely: B, C, D, E, and F. The following routes are possible: A to B, A to C, B to F, C to D, C to E, D to G, E to G, and F to G. For some reason, such places can only accommodate a number of soldiers going through these places. B, C, D, E, and F has a capacity of 3, 3, 9, 6, and 4 soldiers. b. Solve the problem using the Ford-Fulkerson algorithm.
In many races competitors wear a RFID tag on their shoes or bibs. When the racer crosses a sensor a computer logs the racer’s number along with the current time. Sensors can be placed along the course to accurately calculate the racer’s finish time or pace and also to verify that the racer crossed key checkpoints. Consider such a system in use for a half-marathon running race, which is 13.1 miles. In this problem there are only three sensors: at the start, at the 7-mile point, and at the finish line.Here is sample data for three racers. The first line is the gun time in the 24-hour time format (HH MM SS). The gun time is when the race begins. Subsequent lines are recorded by sensors and contain the sensor ID (0=start, 1=midpoint, 2=finish) followed by the racer’s number followed by the time stamp. The start time may be different than the gun time because sometimes it takes a racer a little while to get to the starting line when there is a large pack. 08 00 000,100,08 00 000,132,08 00…
One of the problems with the Internet email system is that sending forged emails is relatively straightforward, i.e., it is easy to send an email with a fake sender/from address. One solution to this problem would be for a domain’s mail servers to digitally sign any email originating from the domain. For this to be useful, the public key would need to be made available to clients to validate the signatures. It is proposed that the public keys of the mail servers will be verified and signed by a certification authority (same as SSL/TLS certificates) and distributed via a standardised URL for the domain, e.g., https://mybusiness.com/email.pubkey. (a) Explain how the client would obtain the public key and validate the email server’s digital signatures. (b) Discuss the problem of trusting the obtained public key and how this solution results in public keys that can/cannot be trusted. (c) Indicate whether you believe this approach could be used to prevent forged emails and explain why it…