AP CSP Semester 1 Final

What is the Internet?

a tangible, physical system that was made to move information; fully distributed; made up of independently operated networks; no central control; internetworking protocol; open, public, shared, plain text

What type of information does the Internet ship?

bits

What is a bit?

a binary pair of opposites (on/off, yes/no, 1/0)

How are bits organized?

8 bits = 1 byte

1000 bytes = 1 kilobyte

1000 kilobytes = 1 megabyte

How do we send bits?

electricity

light

radio waves

bandwidth

the maximum transmission capacity of a device; measured by bitrate

bitrate

the number of bits per second a system can transmit

latency

the amount of time it takes for one bit to travel from sender to receiver

electricity mode

sending through a wire (e.g. Ethernet cable); cheap but signal lost

light mode

fast, no signal loss (e.g. fiber optic cables that reflect light); expensive and hard to work with

radio wave mode

wireless; translate 1s and 0s into radio waves and back into 1s and 0s; signal loss

Vint Cerf & Bob Kahn

Internet founders (early 1970s)

ARPANET

Advanced Research Projects Agency NETwork (department of defense experiment); first Internet

Paul Baran

computer network pioneer; department of defense; came up with the distributed packet-switched network

ISP

Internet Service Provider (AT&T, Verizon, Time Warner) that connects you to other devices

protocol

a well-known set of rules and standards used to communicate between machines

IP address

Internet Protocol; a number unique to each computer or device at the edge of the network; 4 numbers each from 0 to 225, 8 bits per number, 32 bits total

IPv4

4 billion unique addresses; earliest IP system

IPv6

128 bits per address; 340 undecillion unique addresses

DNS

Domain Name System; associates names (www.example.com) with corresponding IP addresses; connected in a distributed hierarchy; open public communication protocol

NAT

Network Address Translation; conserves IP addresses

buffer

memory which stores packets temporarily

DNS spoofing

a hacker matches the domain name with the wrong IP address

direct dedicated connection

NOT how the Internet works

packet

about 1500 bytes; does not travel in a fixed route; each has the "to" and "from" IP addresses; identification serial number for tracking purposes

router

traffic managers that keep packets moving smoothly along paths; connects pathways; chooses the cheapest available path for each packet based on destination; fault-tolerant and reliable

TCP

Transmission Control Protocol; manages sending and receiving of packets at the edge; does a full inventory and sends back acknowledgements of all packets received; packets are resent if necessary

web browser

the app you use to access the Internet (Chrome, Firefox, Safari)

URL

Uniform Resource Locator

HTTP

HyperText Transfer Protocol; the language used to communicate between web browsers and servers

SMTP

Simple Mail Transport Protocol; used for sending email

IETF

Internet Engineering Task Force; working group that adopts protocols

server

what your computer communicates with

"get" request

client request to server to get info on a page and send it

"post" request

request that a web server accepts the data enclosed in the request message's body for storage

cookie

ID number that is stored in your web browser for identification

HTML

Hyper Text Markup Language; tells a web browser how to make a page look (bold, font, italic, image, alignment, etc.)

SSL & TLS

Secure Sockets Layer & Transport Layer Security (https & lock symbol)

digital certificate

official ID card proving it is the website it claims to be

certificate authorities

trusted entities that verify identities of websites and issue certificates for them

How does DNS work?

URL - web browser - operating system - resolving name server - root name server - TLD name server - authoritative name server

Resolving Name Server

knows where to find the root name servers; stores information from servers

TLD

Top Level Domain; .com, .net, .org, etc.

ANS

Authoritative Name Server; most specific (webkinz.com, example.net, gov.org)

What does the invisible dot at the end of .com represent?

the root of the Internet's name space

cache

computer memory that stores past IP addresses so your computer doesn't have to search for it again

encryption

scrambling or changing a message to nide it

decryption

unscrambling an encrypted message to make it readable

Caesar's cipher

shifting each letter a certain number down the alphabet

key

a secret password that only the sender and receiver know for unlocking a message

multiple digit keys

shift each letter a different distance; longer keys exponentially increase amount of time to crack

256 bit keys

typical key lengths today (used to be 128)

symmetric encryption

sender and receiver use the same key to encrypt/decrypt a message (secret key has to be agreed upon ahead of time)

asymmetric encryption

a public key that can be exchanged with anyone and a private key that is not shared

public key

shared with everybody so anybody can encrypt a message

private key

can only be decrypted by a computer with access

computer virus

an executable program that gets installed (usually unintentionally) and harms a user and their computer; can spread to other computers; fake programs, self-installing; can steal, delete, or control information and programs

DDoS

Distributed Denial of Service attacks; work through botnets to overwhelm a website with too many requests

BotNet

armies of infected computers that attack and take down websites

phising

trick people into sharing sensitive information

edge

what we see (your computer and mine)

core

the inside of the Internet; all the computers that connect and pass the message along

net neutrality

carriers are just packet deliverers and can do nothing else

end to end

the switches at the core of the Internet just pass packets and don't know anything else

RFC

Request for Comment; Internet standards adopted through a remarkable process of consensus-building, non hierarchical in the extreme

UDP

another high-level protocol that relies on IP for packet delivery; the packets are put in the Internet and sent on their way with no provision made for data loss; timely but unreliable

Enigma

the early cryptography machine that used a series of wheels to randomize the code used for government secrets

Alan Turing

he made breakthroughs in both code breaking and computer design; worked with the enigma machine; father of computer science

Auguste Kerckhoffs

the safest code is in the system everyone knows; it's safest if the enemy knows your cryptography system

Charles Babbage

an English mathematician, philosopher, inventor and mechanical engineer who is best remembered for originating the concept of a programmable computer

Effective cyber security involves...

human behavior

software

hardware

frequency analysis

allows simple substitution ciphers to be broken based on common word structures

algorithm

a set of steps to accomplish a task; solves a problem and does so efficiently

asymptotic analysis

allows algorithms to be compared independently to see which are the most efficient

pair programming

programmers work as a team (two people, one computer); more creativity and ideas; one driver, one navigator; communication is key

driver

sits at the computer and uses the keyboard and mouse; controls main actions of the computer

navigator

prompts the driver by answering questions and pointing out potential problems or mistakes

RFID

Radio Frequency Identification; similar to barcodes; read by radio waves rather than visible light

EDR

Event Data Recorder; records and stores details about an event

Privacy Act

1974 act mandating that all government files about private citizens be kept confidential

structure

basic unit of programming logic (sequence, selection, or iteration)

sequence

performs actions in order; no branching or skipping

selection

decision; asks a yes/no question and takes one of two actions; if-then

dual-alternative ifs

if-then-else

single-alternative ifs

if-then

null case

situation where nothing is done

iteration

loop; repeats actions while a condition remains true; for, while, repeat

start and end symbol (terminal)

oval

input/output symbol

parallelogram

process symbol

rectangle

decision symbol

diamond

connector symbol (used to connect breaks in the flowchart)

circle

How are programming structures connected?

nested or stacked (NOT interwoven or overlapped)

block

a group of programming statements that execute as a single unit

end-structure statement

indicates the end of a structure (endif, endwhile)

Machine Language

The language a computer understands but people find difficult.

Compiler

A program that converts a Source File into Machine Language.

Project

The Source File and other files needed to make your program work.

System(Pause);

Command that pauses the program and tells the user to "Press Any Key to Continue..."

//

Used to start a comment in a program.