The Internent Flashcards

Question

How do modern search engines function?

Answer 1

- search internet for various keywords - index these with links to where they can be found - this index is made available to all users - can cope with misspellings and provide searches in various languages - make use of meta tags: extra info that web designers add, but do not display, to make it more likely to be found

Answer 2

- Shows the user the most useful websites based on their search. RECURSIVE PROCESS - Used by google. It ranks possible web pages according to external links - if a web page has many links into it from other pages (votes) it is deemed to be popular and more worthy of consideration - not all votes are equal. Some votes more important than others. (This is based on the rank of these pages)

Answer 3

- PR(A) = (1-d) +d (PR(T1)/C(T1) + .... +PR(Tn)/C(Tn)) - PR(A) is the pagerank of page A - PR(Ti) is the pagerank of pages Ti that link to page A - C(Ti) is the number of outbound links on page Ti - d is the damping factor that can be set between 0 and 1

Answer 4

- reduces the ranking on the assumption that a typical surfer will eventually give up clicking and resents the probability that the surfer will continue - set to 0.85

Answer 5

- each time the google spider crawls the web, it recalculates the rank - original algorithm is prone to abuse by those who set up 'link farms' to artificially increase the number of links to favoured pages. Google continues to alter its algorithms to circumvent such problems

Answer 6

- interactions between client and web server which holds resources the client wants - resources can be static or involve multiple transactions (such as making a booking) - decisions have to be made about what processing occurs where. Issues are to do with performance and security

Answer 7

- Reduces load on the server; the server may be busy handling multiple transactions and if some of the processing can be offloaded to client machines, this will speed up activity - user will have better experience if data input is checked there and then without the delays of immediate sending of each item to the server for checking - reduces web traffic; if input data can be validated by a client-side script, this will reduce the likelihood of erroneous data being sent for the server to validate and process

Answer 8

- Data validated by a client-side script may have problems with it; it is still necessary to have further validation at server end - essential for actually querying a DB. It is vital to keep the data owned by an organisation secure, so any processing of that data must take place under the control of the organisation. Therefore SQL processes will largely have to be located at the server end. No sensitive data should be send to the client where it could be intercepted and manipulated

Answer 9

- the compression algorithm builds an index where each data item is recorded along with an index reference - the compressed file then consists of the dictionary plus the sequence of occurrences

Answer 10

- makes use of redundant data, so that if a data item occurs multiple times, the item is stored once in an index along with the number of repetitions - eg; part of an image with many blue pixels old be stored in an index by storing the start location and the number of reps

Answer 11

- online banking payments | - communications involving trade secrets or other sensitive or personal data

Answer 12

- existed for as long as there has been communication - Ciphers used to protect data and the key is needed to return data back to original state (decryption) - keys can be applied in various ways and can be numbers, words or random strings

Answer 13

- key used to encrypt message is also used to decrypt it - both sender and recipient need to know key - some algorithms encrypt one byte at a time whereas others take a whole block of data and pad it to make units of a fixed size - key may be used multiple times or it may be generated for each transaction - danger of a successful attack on symmetric encryption messages, either by intercepting the key or duplicating the key-production process

Answer 14

- requires use of 2 different keys - key used to encrypt is not the same as they key used to decrypt - encrypt key is publicly known and can be used by anyone who wants to send an encrypted message via a publicly known algorithm - the algorithm is implemented using the second, compatible but secret, private key - to decrypt the message the public algorithm is applied with the secret key. Safer but requires more processing power. - keys are typically large random numbers that are unlikely to be guessed

Answer 15

- cam be used to store and check passwords, commonly used for network logins and online transactions. Hash value is used to store password in sever - it is easy to transform plaintext message or password into something else, but very difficult to regenerate the plaintext (or password) from the hash value. If DB is hacked passwords are still secure - Next time user logs in, the Password is transformed using hashing algorithm and result is looked up to see if it matches stored hash value. If it does access is granted - no use for sending messages that need to be decrypted.

Answer 16

- method of hacking where every possible combination of characters is tried one by one - computationally expensive and encryption is designed to make it too much trouble to spend the effort

Answer 17

-common passwords stored in a dictionary and tried out along with hashing algorithms

Answer 18

- the salt is a random string appended to a new password before hashing. - makes the hash value different even for the same password - salt is stored alongside the hash value. To check the password the salt is used to decrypt the hash

Answer 19

Language that does not need a prior declaration of variables before use and creates one when needed during the running of the programme, assigning a data type according to what value is passed to it