comp sci ap exam

Overflow

error that results when the number of bits is not enough to hold the number

Round-off

error that results when the number of bits is not enough to represent the actual number

Lossy

Compressing data in a way that throws some data away and makes it almost impossible to recover the original

Lossless

Compressing data in a way that preserves all data away and allows full recovery of the original

Metadata

data about data

Sequencing

code flows line by line

Selection

a boolean condition to determine which of two algorithmic paths are taken

Iteration

using a looping control structure

Reasonable Time

polynomial in the number of steps an algorithm takes in the worst case based on the input size

Not reasonable time

Usually exponential in the number of steps

Heuristic

using a "rule" to guide an algorithm

Undecidable

A problem that is so difficult

Linear Search

Going one by one vs starting in the middle and going left/right like looking for a word in the dictionary

Binary Search

requires the list to be sorted in order and then cutting the list in half

APIs

Application Programming Interface

Citizen Science

Lots of people to help with a scientific project

Cloud Computing

Using distributed calculations and/or storage for big data or a web application

Crowdsourcing

Asking lots of users online to help with something

Creative Commons

An alternative to copyright that allows people to declare how they want their artistic creations to be shared

Open Access

A policy that allows people to have read access to things

Moore's Law

The # of transistors on a chip doubles every two years

Peer-to-peer Networks

A system where one user's computer connects through the Internet to another user's computer without going through an intermediary "centralized" computer to manage the connection

Digital Divide

The idea that some communities / populations have less access to computing than others

ISP

Internet Service Provider

How does internet communication arrive at its destination?

Speech on the Internet goes from the source to an ISP

How can the government control speech on the Internet?

1) It can try to control the speaker or the speaker's ISP

How can Internet posters evaded being convicted for defamation/slander on the Web?

The posters could evade responsibility as long as they remained anonymous

What has Congress given ISPs relating to an Internet Defamation case?

Congress had given the ISPs a complete waiver of responsibility for the consequences of false and damag- ing statements

Internet Protocol Hourglass

Each protocol interfaces only to those in the layers immediately above and below it

TCP

Transmission Control Protocol
Guarantees reliable transmission by breaking messages into packets

UDP

User Datagram Protocol
provides timely but unreliable message delivery

HTTP

HyperText Transport Protocol
which is used for sending and receiving web pages

SMTP

Simple Mail Transport Protocol
used for sending email.

What does "End to End" mean in regards to the Internet?

"End to End

RFC

Request for Comment
Standards adopted through a remarkable process of consensus- building

Shortcut for going from binary to hexadecimal

To translate a binary numeral (like 11010111012) to hexadecimal

Internet

A network of independent but connected devices all over the world.

World Wide Web

The collection of interlinked website documents (such as HTML files) that you can view with a web browser by typing addresses like http://bjc.berkeley.edu/website/privacy.html.

HTML

Hypertext markup language
Most web pages are written with

URL

Uniform Resource Locator
An address for accessing specific web data located on a server

Server

A computer hosting data for others to access

Protocol

the standard for communication between browsers and servers (usually "http" or "https")
Sometimes not visible in browsers like Google Chrome

Domain Name

The name of the server that hosts the data
(bjc.berkeley.edu)

Path

the location of the data in a hierarchy of folders on the server
(Website/privacy.html)

Protocols

Standards for communication

IP

Internet Protocol
An addressing system that finds paths to distant computers
Specifies how a router handles a request for another IP address.

Redundant

There are multiple pathways among the physical connections of the Internet to create redundancy. Even if one pathway is unavailable

Hiearchial

There are two Internet addressing systems

Fault Tolerance

ability to work around problems

Scalability

the ability of the net to keep working even as the size of the network and the amount of traffic over the network increase.

Virus

A kind of malware that tries to spread itself over the network to other computers.

Antivirus Software

Helps protect against virus attacks

Phishing

An attacker sends you an email that appears to be from some official organization (such as your bank) and tricks you into giving information to the attackers (such as your bank password).

DDoS

Distributed Denial of Service
-Consists of sending a lot of requests to a server at the same time. This can overload the server's network bandwidth.
-Causes a temporary inability to reach the targeted server so other users of that server are denied service.

Which protocols are used to keep secure HTTP connections?

Transport Layer Security (TLS) or maybe an older version called Secure Sockets Layer (SSL)
With these protocols

Certificate Authorities

Used by many websites for encryption to protect files and information that is transmitted over the Internet. They issue certificates to verify the identity of a user or computer.

Public IP Address

The IP address that is logged by various servers/devices when you connect to them through your internet connection.

Private IP Address

An IP address that's reserved for internal use behind a router or other Network Address Translation (NAT) device

IP v4

This address is big enough to support 2^32 computers. That's about four billion (4 · 109)

IP v6

The long-term solution is to increase the length of an IP address. The new IP addresses are 128 bits wide

Routers

The "connection points" of the Internet.
Networking devices that route traffic between subnetworks on the Internet.

Packets

When you send a message over the Internet

Packet Switching Network

A digital networking communications method that groups all transmitted data into suitably sized blocks

Hierarchy of Abstractions

Manages the complexity of the Internet by hiding the details of lower levels of the system. The highest level of abstraction includes the most general features of the Internet that have to work the same across all devices. At lowers levels of abstraction

Application Layer Protocols

The highest level of abstraction because they manage how data is interpreted and displayed to users. These protocols give meaning to the bits sent by lower-level protocols

user and server computers must agree on what the bits mean

and application protocols (like HTTP) offer this.

Transport Layer Protocols

Manage the breakdown of a message into packets to be transmitted by lower level protocols and also the reconstruction of the message from the packets upon arrival.

Internet Layer Protocols

Manage the pathways that the data packets travel across networks. These protocols treat the Internet like one large network even though the physical reality on the lower level is one of many tiny subnetworks.

Network Interface Hardware

Also known as Link Layer
All Internet devices connect through a physical interface that uses a protocol to manage the connection to the local network. These local protocols are the least abstract because they deal directly with your physical hardware.

DNS

Domain Name System
The hierarchical addressing protocol that is human-readable

Who is in charge of the Internet?

The computers on the Internet and the connections among them don't belong to any one organization.

ICANN

the Internet Corporation for Assigned Names and Numbers
Controls the DNS hierarchy and the allocation of IP addresses.

For how long has the U.S. dominated the Internet and why?

The U.S. has "controlled" the Internet up until 2009. The Advanced Research Project Agency (ARPA) first developed the Internet in 1969.

Open Protocols

Standards that are not owned by a company

IETF

(The Internet Engineering Task Force) and the Internet Society oversee Internet protocols

What does the Internet rely on to operate properly?

The internet relies on the cooperation of many different elements.

Firewall

Used to limit the kinds of connections (HTTP requests

Cipher

The set of rules you are using to encode the information

Key

What tells you how to arrange the cipher's rules. _ is applied using an algorithm to a string or block of unencrypted text to produce encrypted.

Deciphering

Analyzing the code and working back from it

Monoalphabetic Cipher

A class of ciphers where the code is based on one letter of the alphabet standing for another letter consistently throughout the message

Brute force

Trying all the possible ways to crack a code

Frequency Analysis

Based on the idea that every language has its own specific patterns. The study of the frequency of letters or groups of letters in a ciphertext.

Crib

Words

Polyalphabetic Cipher

The way you scramble the alphabet actually changes throughout the message
Example: Vigenère cipher

Vigenère Square

Alphabet goes up on the top and also to the side in order to help write a code.

How can you crack Vigenère cipher?

By using a type of frequency analysis developed by Charles Babbage. Babbage realized that some patterns in a long message may still show up and he counted how many letters separated those repeated patterns.

One time pad encryption

Only way to create an unbreakable cipher. Uses the key that is as long as the message itself. Once a sheet is used for a message you destroy it. Then you use the next sheet for the next message so you never repeat a key. As long as you keep the pad safe

The Enigma Machine

An example of a one time pad encryption device.

The British Bombe

Device developed by Alan Turing used by the British military to crack the enigma machine. As long as this device knew 20 characters of the message it could crack the code.

Prime number

Numbers only divisible by themselves and one. Very useful for internet security because of this trait.

Public Key

A code that is available for anyone to use.

Private Key

A code that must remain confidential to its respective owner.

How does Public Key/Private Key Cryptography work?

Example: If Bob wants to send sensitive data to Alice

Encryption

Works by converting information or data into a language that cannot be understood in one glance. Usually

Three principles of Encryption?

1) Authentication
2) Integrity
3) Non-repudation

Authentication

Helps to verify that original author of the code is what he or she claims to be.

Integrity

Essential towards maintaining the privacy of the message because it must be known that the message was not tampered with in any way

Non-repudiation

Where the user sends a message to another person but later denies he or she actually sent the message

Three types of encryption?

1) secret key cryptography
2) public key cryptography
3) hash functions