Proficient Key Tree Structure for Secure Dynamic Groups

Proficient Key Tree Structure for Secure Dynamic Groups Secure Group Communication ensures forward secrecy and backward secrecy of the data. It is the responsibility of the Group Center (GC) to disallow new members to have access to previous data called backward secrecy and existing members who have left the group to have further access to data called forward secrecy. Forward and backward secrecy can be ensured by updating the keys whenever a join/leave request is handled. This process is called as re-keying. The tree structure is appropriate for maintaining keys. Most of the schemes use binary tree structure for maintaining keys. The Key tree structure uses three kinds of keys such as Traffic Encryption Key (TEK), Key Encryption Key (KEK) and Individual Key (IK). TEK is the top level key called Group key, KEKs are the intermediate level keys called subgroup keys and IKs are the leaf level keys. Figure 3.1 shows the binary tree with 3-levels, which keeps keys at all levels. Based on the number of levels in the binary tree, the height of the tree (H) is calculated. Therefore the height H is 3 since there are three levels in the binary tree. Multicast group members are inserted into the tree only at leaf level. The number of nodes is 2n+1-1 and group members are 2n where ‘n’ is the number of levels in the tree. Here, there are eight members in the multicast group and are represented by M1 to M8. The top level key K0 is the TEK, K1 to K6 are KEKs and IK1 to IK8 are the member’s private keys. Figure 3.1 3-level Binary Tree In the key tree based group key management, the Key Centre (KC) delivers new keys to the group members by encrypting them with older keys. Then, the group members have to decrypt the encrypted keys with their old keys. All these encryption and decryption computations amplify the load on KC, resulting in delay to espouse the group key. It also increases power consumption to acquire the new group key. All keys must be stored in the memory of communication devices and group members have to accumulate the group keys in a secure memory like Universal Subscriber Identity module (USIM) to safeguard from various kinds of attacks and intrusions. Also, each program requires memory to reserve their secure keys. Since the memory space is limited, the number of keys to be stored must also be minimised. Keeping these constraints in sight, this work suggests the proficient key tree structure, considering the efficiencies of computation and storage costs. 3.1 PROFICIENT KEY TREE STRUCTURE (PKS) The proficient key tree structure consists of two parts in which the lower part constitutes of binary trees to minimise the communication cost and the upper part consists of flat trees up to 2 levels to alleviate the key computation and key storage costs. The TEK is directly connected to the KEKs on the top part of the tree so that it is a subset of the level homogeneous tree. Figure 3.2 Proficient Key Tree Structure with 1 flat level Figure 3.2 shows the proficient key tree with 1flat level and 1 binary level. A Flat tree is used for reducing the computation and storage costs. From the binary key tree, one TEK, 6 KEKs and 8 IKs are stored for 8 members at three levels. Compared to the 3-level binary key tree, l-flat level PKS maintains all 8 members at 2 levels and it requires 1 TEK, 4 KEKs and 8IKs. The number of KEK is reduced if flat tree is used. This reduces key storage and key computation costs. In case of 2 flat levels and 1 binary level, 1 KEK, 16 KEKs and 32 IKs are maintained for 32 members at 3 levels. Figure 3.3 shows the proficient key tree with 2 flat and 1 binary level. Joining and Leaving are two important operations in a multicast group. Figure 3.3 Proficient Key Tree Structure with 2 flat levels and 1 binary level If the member M24 wants to leave the group, some key updates are required for maintaining confidentiality and integrity of data. The keys K0, K3 and K16 should be updated as a part of re-keying process. The Key Centre selects a key for encryption of the new key and this new key must be kept secret from the leaving member. This ensures the property of forward secrecy. 3.1.1 Batch Re-keying When multiple members want to leave from the multicast group, the key updates are done as a batch called batch re-keying (Li et al 2001). In batch re-keying, the interval for which key server waits, is termed as re-key interval. The entire join and leave requests are collected during this re-key interval to generate new keys. Moreover, it also constructs a re-key message and multicasts it. Batch re-keying improves efficiency because the number of re-key messages to be signed is reduced. One message is signed for a batch of requests unlike one for each. Batch re-keying takes advantage of the possible overlap of new keys for multiple re-key requests. 3.1.2 Join Operation When a new member (Ui) wishes to join the group, the member has to send a request. In addition to the information of existing group members, the Key Distribution Center requires the new level K’ to insert the member into the tree (Figure 3.4). If the performance of the joining member is worst, then the new level K’ should be smaller than the level of present key tree structure (K). The following steps are followed to join the member in the multicast group. Step 1: Receive join request from the new member to the multicast group Step 2: Determine the level of the current tree, K and new level required K’ Step 3: If K’ is greater than or equal to K, check whether the tree is complete Step 4: If the tree is a complete tree, broadcast the remove key message that are on the same level K Step 5: If K’ is less than K, set K as K’ and check whether the tree is complete. Step 6: If the tree is complete, broadcast remove key messages that are on a higher level than or same level as K’ else broadcast that are on a higher level than K’. Figure 3.4 Key tree updates when user joins From the first part of the Figure 3.4, eight members are on the leaf level and the height of the lower part of the tree K is 2. If the member U9 joins into the tree, it is inserted at the leaf level. It requires one more level since the tree is complete. Therefore, the new level K’ is 3. In order to make the tree into a PKS tree, it needs to maintain the same level and the flat level is to be introduced. Therefore, the existing key tree structure is to be updated and it looks like the second part of the Figure 3.4. K1 and K2 are removed and the top level node is directly connected to K3, K4, K5 and K6 nodes after adding the new member at the leaf level. Figure 3.5 Join Operation in the PKS tree If K’ is greater than or equal to K, the KC need not to change the key tree level, excluding the case when the present key tree is a complete K-level PKS. In case of complete PKS, the key tree structure needs one more level to accommodate new members and to do so, KC should broadcast the remove key message to exterminate the KEKs in level K as in Figure 3.5. If K’ is less than K, it indicates that the height of PKS needs to be lowered from K+1 to K’+1 in order to support the new member. As lowering the height increases the communication cost depends on KC whether to accept the new join request or not. If such addition increases the communication cost, then Key Centre can reject the request. If the tree is complete PKS, KC has to broadcast the remove key message for removing the KEKs on same or higher level than K’. 3.1.3 Leave Operation If a group member wants to leave, it has to send a ‘Leave Request’ to the Key Centre. After receiving the request from the member(s), KC has to update the subgroup keys to maintain confidentiality and secrecy of communication. After updating the group keys, it may be a case that the height of the tree is changed due to the empty positions created as a result of leaving members. In such scenarios, height is recalculated for the tree structure’s lower part i.e. K†. In addition to this, if a group member leaves the group then the height of the tree is updated. Thus, a newly required level K’ is determined by considering the memory space and computation power of the remaining members. The following steps are followed to leave the member into the multicast group. Step 1: Receive a leave request from the member Step 2: Update new KEKs Step 3: Recalculate the height of the changed tree, K’’ Step 4: Determine a new required level K’ Step 5: If both K’’ and K’ are not equal and heightening the level of the tree, create levels from K’’+1 to K’. Figure 3.6 Key tree updates when a user leaves From the Figure 3.6, the member U9 wants to leave the multicast group. K is 2 and the height of the lower part of the changed key tree K† is 1. If K† is smaller than K, the KC decides to heighten the height of the tree. If it so, it generates new KEKs on level two. If K† is equal to K’ then the height of the changed key tree is same as the height of key tree which is required for communication. In this scenario, no changes will be done in the height of the key tree structure. If K† Figure 3.7 Leave operation in the PKS tree 3.2 PERFORMANCE METRICS The performance of the PKS tree structure is evaluated in different aspects of costs such as Key computation, Key storage. 3.2.1 Key Computation Cost In a key tree structure, three keys are considered. They are group key (TEK), subgroup key (KEK) and Individual Keys (IK). As the level in a key tree structure increases, the number of keys for the group or member also increases. The depth of a binary tree equals to the integer part of log2n, where‘n’denotes the number of nodes on the balanced tree. The PKS tree maintains two types of levels. They are the flat levels (fl) and binary levels (bl). The height (H) of the tree is the number of flat and binary levels, i.e., H=fl+bl. Each member has one key on each level. Therefore, the number of key computations is same as the height of the key tree. 3.2.2 Key Storage Cost Key storage cost is defined as the number of keys stored by each member in the multicast group and KC. Each member has to store one key on each level. Therefore, it is the height of the tree ‘fl+bl’ for the PKS tree and ‘bl’ for the binary tree. 3.3 SUMMARY Proficient tree based re-keying algorithm is proposed so that it reduces the number of re-keying operations per join/leave request. The Proficient Key Tree Structure has two parts in which the lower part constitutes of binary trees to minimise the communication cost and the upper part consists of flat trees to alleviate the key computation and key storage costs. The time efficiency of all key tree structures is based on the height of the trees. The height is the number of binary levels of the binary tree and the height of the PKS tree is based on the number of flat and binary levels. It is concluded that the time efficiency of the PKS tree is less than the binary tree since the height of PKS is lesser than the binary key tree for the specified number of members in the multicast group. Thus, the proficient key tree structure for re-keying is proposed in this chapter. It gives the complete picture about joining and leaving of users in the multicast group and the key computations during re-keying operations. Multilevel encryption and decryption using graceful codes are discussed in the following chapter.

Behaviors related to microeconomics concepts

Most of us have always wondered why this always happen when they visit a barber. This is just because of the economic concept. The cost of operations in shaving the beards is even more because more care is needed while shaving and different customers have different styles on how they it to be shaved. This wastes time and energy and to pay for this, the price has really to be high. The expenses that are incurred when perfuming this service is the same with that one that you will apply when performing other services and hence there is no reason whatsoever for its price being low.Another factor is the skill factor in that while shaving the beards, more skill is required and this is reflected in price. As much as in shaving the head any other barber can do it the beard shaving requires potential and qualified barbers and it is this that makes the prices improve upwards. (Perloff, M. J 1999) Why does it cost higher for a woman delivering in a private hospital than that one delivering in a government hospital? Most of the women who go in private hospitals are considered as working class.Although the services rendered may be the same as those in public hospital most of them will prefer going I n private hospitals because of their status. most of the consumers do consider social class as a factor while purchasing products or services in the market like if a dress is sold in the market at $8, and the same dress of the same quality from the same company is sold in a beauty mall at a price of $ 15, a consumer who considers herself as from high class will rather go for that dress in a shopping mall than that one in the market because she tends to think that her status does not allow her to purchase in markets.In fact producers take this as opportunities that they think should be utilized and increase prices in high class shops and reduce in low class shops to just increase the total sales in their organization. The doctors on the other hand, will want to serve more clients within a short time to increase their portfolio income but affect the customers by attending more in less time. The real money in a consumer’s portfolio is the one that will determine where he should seek his service. It is actually this factor that determine where and what a consumer should purchase depending on his capability to pay for the services rendered.That is why high qualified doctors can decide to open their own clinic that will cater for another class of people thus serving the needs of most of the consumers in the market. In today’s market, the key point is actually identifying the need of the customer and fulfilling it. (Mas-Colell. A. et al 1995). Why are veils quite expensive in US than in Saudi Arabia? If there are so many customers in Saudi Arabia who need to purchase this commodity, then how come it is still cheap there yet the demand is also high! The prices should have actually gone up to cut down on the demand .This is not the case because of thi s culture factor that most organizations need to consider. Most of the people in Saudi Arabia are Muslims and thus most of them need veil as a requirement because of their faiths. This is unlike the customers us who may be assumed as just those who want it for luxury. The way the veil is taken as a cloth required during the worship is not the way it will be taken in the US market hence the prices will probably go high. Culture being important in the consumer behavior has a real impact in any organization.If a customer perceives that a certain commodity is the best however much it may tend to be expensive, a customer will sacrifice and ay the premium price for this commodity than purchasing another commodity that he has no confidence with it. (Pindyck, R. et al, 2004) Bibliography Mas-Colell. A. et al (1995), Microeconomics Theory, Oxford University Press Perloff, M. J (1999), Microeconomics: Incentives in an Imperfect World, Addison-Wesley Longman. Pindyck, R. et al, (2004), Microec onomics, Pearson Prentice hall

Choosing Media Bias Essay Topics Is Simple

Choosing Media Bias Essay Topics Is Simple The world has gotten more democratic than in the conventional times. You still must compose a mass media essayand you have to begin on it pretty soon in the event that you want to have it done before the deadline! This bit of information concerning the shooting does not seem any place in the NEWSMAX article. The Washington Post story the next day set the group's name at the very start of the report. Ideas, Formulas and Shortcuts for Media Bias Essay Topics Studying media can be very intriguing and fascinating, although the science of media changes every time as soon as the new media source is introduced. Language might also be classified as a political component in the media. Reporting in the contemporary media is much better than traditional media because everyone would like to create the very best news. Consequently in addition, it becomes quite important to comprehend and gain a `media literacy' that can teach us to deal with the current cultural atmosphere. A huge portion of the media is biased. Since there are lots of diverse kinds of media on the planet and since different folks prefer various media as their source of information, the option of media and the method by which the dilemma of information security is presented in each media is quite significant in making decisions along with shaping people's ideas and attitudes. Twitter is an excellent means to send out information, but it's risky to do so as it can create a really biased atmosphere. The one-sided collection of information in the media may produce a distorted image. At first you ought not relate to a single source only. In order to totally appreciate and analyze this, it is neces sary to check at three different news sources and the way they report the identical matter. The Appeal of Media Bias Essay Topics No surprise, the essays from their hands are only an ideal mix of expertise and writing skills they've acquired in the area. To get essay online, you merely will need to fill in the application form and you'll get excellent work on the desired topic. Researching the topic permits you to find out more about what fascinates you, and should you pick something you truly like, writing the essay will be more enjoyable. Moral argumentative essay topics are a few of the simplest to get carried away with. Portraying the motherly appeal is something that may be quite effective especially where security is the most important concern. Pay close attention to all things electronic, and you will be certain to find something debatable of what you see. When you're picking your topic, remember that it's much simpler to write about something which you presently have i nterest ineven in case you don't know a good deal about it. One expresses prejudice behaviors when they're uncomfortable about things that aren't like their own self. Now let's look at bias by story selection. One particular modern accusation of media bias in america concerns the continuing Israeli-Palestinian conflict. Be alerted to ascertain whether there are rival causes and in the event the evidence is deceptive. Prejudice is usually practiced from the other side of the world. Conclusion Social bias is an enormous part of international history. The Media Bias Essay Topics Trap Media bias happens when the media seems to push a particular viewpoint, instead of reporting the news objectively. With the rise of internet news and media, it will become important to grasp the importance of media outlets and their relative bias. Remember that media bias also occurs whenever the media seems to ignore an important element of the story. Quite often, the media is accused of being the absolute most unfair when reporting news related to politics, particularly during presidential elections. A news reporter might need to learn the facts, and a sports reporter may be trying to learn the way the team is going to be impacted. NBC news will offer a really left of center outlook on all the country's political stories that it posts, Fox News will offer an exact right of center outlook on basically the exact stories, and CNN will supply an exact factual account that's an incredibly neutral form of the true event or issue. Fox News is a quality instance of a biased news station. The news needs to be based on real-life incidents and facts but there always seems to be distorted information from various media broadcasts. The Argument About Media Bias Essay Topics Ultimately, solutions that help with overcoming social biases are provided. Students lead busy lives and frequently forget about an approaching deadline. This race is likely to get ugly. In some ways, interest groups may also weaken American democracy since if there are lots of distinct factions, no particular interest group is going to have more power than the other. How mass media is supporting politicians to modify the mind of the people who live in the country. The very same for folks of different races.

The Market A Target Market Segmentation - 1915 Words

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