The Internet, the WWW and Encryption Flashcards
(27 cards)
What are the types of scripting?
- Client-sided scripting
- Server-sided scripting
What is client-sided scripting?
Processed entirely in the browser.
It is often embedded in HTML code but can also be a separate file (external script). The script is sent from the web server to the client where the client web browser executes the script.
User enters URL with embedded script ->WEB BROWSER->Browser requests page with embedded client-side script->WEB SERVER->Web server delivers requested web page with embedded script->WEB BROWSER processes script and displays
What is server-sided scripting?
Processed at the server level and resultant HTML passed back to browser.
Client submits request to Web Server. Script is processed by engine and HTML is passed back to Web Server. Web Server sends resulting page back to client.
Different servers process requests differently (e.g. server may link particular file extension to initiating a script). Parameters can be passed alongside this.
What are client-side scripting languages?
JavaScript
ActionScript
Dart
VBScript
Typescript
Python
What are the advantages of client-side scripting?
- Speed - code can be run immediately instead of having to contact server and wait for the answer - allows for more interactivity
- Simplicity - easy to learn
- Versatile - interactive with other languages and can be inserted into web pages regardless of the file extension
- Reduced server load - it is run on the client
What are the disadvantages of client-sided scripting?
- Security - code executed on the user’s computer and can be used maliciously
- Compatibility - needs to be run in a variety of browsers therefore more quality assurance required otherwise could get unpredictable results
What are some server-side scripting languages?
- ASP
- ColdFusion Markup Language
- JavaScript
- Perl
- PHP
What are the pre-requisites for server-side scripting?
- Web server must have appropriate scripting engine installed (otherwise an error will be generated)
- The web page name must have the correct file extension (e.g. .php, .asp) (otherwise the web server will simply return the page as HTML and the script will be ignored)
What are the advantages of server-side scripting?
- Well adapted to work with databases (e.g. online shopping, social networking sites) - more efficient and secure to run a server-side solution
- No issues with compatibility with client browser - script is not being run in the client browser
- Can be run independently of client PC settings (e.g cookies etc.)
- Script cannot be seen in client browser because stripped from HTML code by parser (scripting engine) - useful for developer protecting investment
What are the disadvantages of server-side scripting?
- Software - requires scripting software to be installed on server
- Speed - page loading can sometimes be slow if server is busy and scripts are processing large amounts of data
What is data encryption?
Sending sensitive information across the internet in a secure manner (e.g. credit card information or private correspondence), as well as protecting stored data. Encryption allows only authorised parties to view the information. It does not prevent interception of data ‘in transit’ but it denies the message content to the interceptor by making it unreadable.
What are the two types of data encryption?
- Symmetric
- Asymmetric
What is symmetric encryption?
A secret key is applied to text of message which changes the content in some way (e.g. shift letters by a number of places in the alphabet). If both the sender and receiver both know the key, all messages can be easily decrypted.
Same key to encrypt and decrypt
What is AES?
Advanced Encryption Standard
Used 128-, 192- or 256-bit keys for encryption
What is a disadvantage of symmetric encryption?
The key must be kept secret which is difficult if exchanging over the internet or a large network - secure channel needed which is difficult
What is DES? And why has it been superseded?
Data Encryption Standard which encrypts data using a 56-bit key but because computers have become so advanced, 56-bit encrypted data can be deciphered within a few minutes so no longer considered secure.
What is asymmetric encryption?
Two related keys (key pair) - a public key freely available to everyone and a private key kept secret. The key pair are mathematically linked. A message encrypted by the public key can only be decrypted by applying the same algorithm but by using the matching private key, and vice versa. Means that you do not need to worry about passing public keys over the internet.
What is a disadvantage of asymmetric encryption?
Slower than symmetric because it requires far more processing power (longer key lengths and more complex algorithms)
What is IANA?
Internet Assigned Numbers Authority
What is the IANA responsible for?
Management of root DNS, coordination of IP addressess, protocol assignments
What is ICANN?
Internet Corporation for Assigned Names and Numbers (independent)
What is HTML?
HyperText Markup Language
- describes web pages
- written in elements which include paired tags, with content in between
- web browsers interpret and turn into web pages
What is a web browser?
Interprets HTML to render webpage
Calls HTTP methods against web server
How does the web server and web browser communicate?
HTTP: communication of “web traffic”
TCP/UDP: for packet transfer
IP: network addressing
