Securing Client/Server Transactions Essays -

Securing Client/Server Transactions Securing Client/Server Transactions Securing Client/Server Transactions The three basic ways that security is implemented in the area of client/server transaction. The first area is firewalls. The basic idea of a firewall to monitor traffic from a trusted network ( a companys internal network) to an untrusted network (such as the Internet). Firewalls fall into two categories, proxies and packet-filtering firewalls. Packet-filtering determines whether a packet is allowed or disallowed depending on the source of the packet and the contents of it. Packet-filtering also looks at the source and destination ports, and to determine if a packet is part of an ongoing conversation. An application-level firewall, better known as a proxy acts as an intermediary between the client and the server. The client application connects to the proxy. The proxy opens a connection to the server and passes information back and forth between the server and the client (refer to Figure 1.). Figure 1. Both firewalls have their advantages and disadvantages. In most cases both categories will be implemented on the same firewall. A packet-filtering firewall tends to be less secure than a proxy based firewall, since complete knowledge of the protocol is used by the application. However packet filtering can allow a concept known as masquerading. Masquerading is when the firewall takes the outgoing source address on the packets and converts the address so the receiver thinks they are talking to the firewall. The receivers packets will have its address on it coming back so the firewall can determine which sender gets the packet. The advantage of masquerading is that a companys internal network can be hidden behind the firewall. Another security implementation is encryption. Encryption is the process of modifying information so that it can not be read by anyone except the intended recipient. This is done by applying mathematical algorithms that require a key to unlock, or decrypt, the original data. Algorithms that use the same key to encrypt and decrypt data are known as symmetric encryption algorithms. Algorithms that use different keys to encrypt and decrypt data are known as asymmetric or public-key encryption algorithms. Encrypted data comes in two forms 40-bit and 128-bit. 40-bit encryption uses a 40 bits of space to encrypt data and 128 bits of space for the 128-bit form. The process of verifying the senders identity is known as authentication. Authentication can be performed with a user name and password, or with a piece of information known as a digital certificate. A digital certificate contains encryption parameters, which can be used to uniquely identify a user or a host system. Verifying that an external party has not modified data is known as integrity checking. Integrity checking is done by applying a mathematical algorithm, known as a hash, to data before its sent and computing the same hash when the data is received. If the two hashes map to the same result, then the data hasnt been modified. How do these areas affect client/server transaction? Client/server transaction deals with the everyday transactions that people engage in on the Internet. With each transaction, personal information is sent from client to vendor. The information has a tendency to be sensitive in nature and not something shared with anyone except the vendor. Such information may include social security numbers, credit card numbers, and possibly information for monthly bills (account numbers and balances specifically). Businesses have to save-guard their customers in order for their customers to feel secure in buying products and services from them. Businesses understand this importance. Some businesses and development groups have evolved from the need to make business transactions more secure on the Internet. In doing so, business presence has grown exponentially over the last decade. Commercials on TV tell business owners if they arent on the web, they wont survive. Programmers face difficult and exciting challenges in the areas of security for client/server transaction. One of the most popular languages used on the Internet is Java. Java runs on many different platforms, which makes it very versatile in Internet applications. JavaSoftTM has introduced the Java Commerce Client (JCC) framework. The JCC provides a secure, robust, and reliable platform that enables software vendors to write electronic commerce applications. With a framework, you focus on the application-specific

Building Sentences With Adverb Clauses

Building Sentences With Adverb Clauses Here well practice building sentences with adverb clauses. Like an adjective clause, an adverb clause is always dependent on (or subordinate to) an independent clause. Like an ordinary adverb, an adverb clause usually modifies a verb, though it can also modify an adjective, an adverb, or even the rest of the sentence in which it appears. Adverb clauses show the relationship and relative importance of ideas in our sentences. From Coordination to Subordination Consider how we might combine these two sentences: The national speed limit was repealed.Road accidents have increased sharply. One option is to coordinate the two sentences: The national speed limit was repealed, and road accidents have increased sharply. Coordination with and allows us to connect the two main clauses, but it doesnt clearly identify the relationship between the ideas in those clauses. To clarify that relationship, we may choose to change the first main clause into an adverb clause: Since the national speed limit was repealed, road accidents have increased sharply. In this version the time relationship is emphasized. By changing the first word in the adverb clause (a word called a subordinating conjunction), we can establish a different relationshipone of cause: Because the national speed limit was repealed, road accidents have increased sharply. Notice that an adverb clause, like an adjective clause, contains its own subject and predicate, but it must be subordinated to a main clause to make sense. Common Subordinating Conjunctions An adverb clause begins with a subordinating conjunctionan adverb that connects the subordinate clause to the main clause. The subordinating conjunction may indicate a relationship of cause, concession, comparison, condition, place, or time. Heres a list of the common subordinating conjunctions: Cause asbecausein order thatsinceso thatExample:Im not a vegetarian because I love animals. Im a vegetarian because I hate plants.(A. Whitney Brown) Concession and Comparison althoughasas thougheven thoughjust asthoughwhereaswhileExamples:You will find that the State is the kind of organization which, though it does big things badly, does small things badly, too.(John Kenneth Galbraith)It is a waste of energy to be angry with a man who behaves badly, just as it is to be angry with a car that wont go.(Bertrand Russell) Condition even ififin caseprovided thatunlessExample:If you have ever lain awake at night and repeated one word over and over, thousands and millions and hundreds of thousands of millions of times, you know the disturbing mental state you can get into.(James Thurber) Place wherewhereverExample:Read over your compositions, and wherever you meet with a passage which you think is particularly fine, strike it out.(Samuel Johnson) Time afteras soon asas long asbeforeoncestilltilluntilwhenwheneverwhileExample: As soon as you trust yourself, you will know how to live.(Johann Wolfgang von Goethe)Practice in Building Sentences with Adverb Clauses These five short exercises in sentence combining will give you practice in developing sentences with adverb clauses. Follow the instructions that precede each set of sentences. After you have completed the exercise, compare your new sentences with the sample combinations on page two. Combine these two sentences by turning the second sentence into an adverb clause beginning with an appropriate subordinating conjunction of time:In a Junction City diner, a sunburned farmer comforts his squirming son.His wife sips coffee and recalls the high school prom.Combine these two sentences by turning the second sentence into an adverb clause beginning with an appropriate subordinating conjunction of place:Diane wants to live somewhere.The sun shines every day there.Combine these two sentences by turning the first sentence into an adverb clause beginning with an appropriate subordinating conjunction of concession or comparison:Work stops.Expenses run on.Combine these two sentences by turning the first sentence into an adverb clause beginning with an appropriate subordinating conjunction of condition:Youre on the right track.Youll get run over if you just sit there.Combine these two sentences by turning the first sentence into an adverb clause beginning with an appropriate subo rdinating conjunction of cause:Satchel Paige was black.He was not allowed to pitch in the major leagues until he was in his forties. After you have completed the exercise, compare your new sentences with the sample combinations below. Sample Combinations Here are sample answers to the exercise on page one:  Practice in Building Sentences with Adverb Clauses. In a Junction City diner, a sunburned farmer comforts his squirming son  while  his wife sips coffee and recalls the high school prom.(Richard Rhodes,  The Inland Ground)Diane wants to live  where  the sun shines every day. Even though  work stops, expenses run on. Even if  youre on the right track, youll get run over if you just sit there.(Will Rogers) Because  Satchel Paige was black, he was not allowed to pitch in the major leagues until he was in his forties.