AP COMP SCI
what feature of DNS and IP allow the internet to scale?
Hiearchy
SSL/TLS
Secure Sockets layer / Transport Layer Security - An encryption layer of HTTP that uses public key cryptography to establish a secure connection.
which of the following statements about lossless image format, like PNG, and lossy image formats, like JPEG, is true?
lossy image formats sacrifice detail within an image in order to achieve smaller file sizes.
what is the best term for this type of " data about the data"?
metadata
many websites can express colors in the form of an RGB or six digit hexadecimal value. what hexadecimal value is equivalent to RGB (175, 84, 192)?
#AF54C0
when web developers specify color value for text or backgrounds, they often represent RGB colors using a six-digit hexadecimal value in which the first two characters represent the red component of the color, the middle two characters represent the green component, and the final two characters represent the blue component. you want to configure the text on your blog to use a slightly darker shade of purple than the one you have seen used on another website. the purple used on that site has an RGB value of #7F20FF. which of the following RGB values would produce the darker shade of purple that you desire for your blog?
#3F107F
Bit rate
(sometimes written bitrate) the number of bits that are conveyed or processed per unit of time. e.g. 8 bits/sec.
Consider the following three binary numbers: 01010 010000 1110 Which of the following lists the numbers in order from least to greatest?
01010 1110 010000
Approximately how much bigger (how many more bytes) is a megabyte than a kilobyte?
1,000 times bigger
Which of the following most accurately describes Moore's Law:
Moore's Law is the observation that computing power tends to double every two years
What is the 4-bit binary number for the decimal number Ten (10)?
1010
you have a coordinate grid that is 96x96. Assuming that you encode the x and y coordinate as separate numbers, what is the minimum number of bits that you will need to encode a coordinate in that space?
14
A video-streaming Web site uses 32-bit integers to count the number of times each video has been played. In anticipation of some videos being played more times than can be represented with 32 bits, the Web site is planning to change to 64-bit integers for the counter. Which of the following best describes the result of using 64-bit integers instead of 32-bit integers?
2^32 times as many values can be represented.
Two students have developed a protocol in which they send 4-bit messages to each other. They decide to modify their protocol to start sending 8-bit messages instead. How many more values can be represented in an 8-bit message than a 4-bit message?
2^4 = 16 times as many values
the fundamental unit of a digital image, typically a tiny square or dot that contains a single point of color of a larger image.
Pixel
The world is currently in a transition to using IPv6, a newer version of the IP protocol that uses 128-bit addresses instead of 32-bit addresses used by IPv4. What is the main problem that IPv6 was created to solve?
2-bit addresses could not ensure that every internet-connected device can receive a unique IP address
What is the minimum number of bits you would need to encode the 26 letters of the alphabet plus a space - a total of 27 characters?
5 bits
the standard QWERTY keyboard has 47 keys that can place characters on the screen. Each of these keys can also display a second character by holding the "shift" key at the same time. How many bits would you need to encode everything that could be types on this keyboard?
7
Pick the two expressions involving the Modulo operation that compute to the exact same value (choose 2)
9 MOD 8 1 MOD 16
8 bits is enough to represent 256 different numbers. How many total bits do you need to represent 512 (twice as many) numbers?
9 bits
Choose the answer that is NOT a feature of Public Key Cryptography:
A Public Key database ensures 3rd party accountability of security
One-pager
A business/corporate term for a one-page document that summarizes a large issue, topic or plan.
bit
A contraction of "Binary Digit". A bit is the single unit of information in a computer, typically represented as a 0 or 1.
Internet
A group of computers and servers that are connected to each other.
The Internet Engineering Task Force (IETF) defines the protocols and standards for how the Internet works. The members of the IETF are:
A loosely organized collection of citizens and engineers.
innovation
A new or improved idea, device, product, etc, or the development thereof
IP address
A number assigned to any item that is connected to the Internet.
Which of the following statements are true about routers and routing on the Internet. Choose two answers.
A packet traveling between two computers on the Internet may be rerouted many times along the way or even lost or "dropped". Routers act independently and route packets as they see fit.
protocol
A set of rules governing the exchange or transmission of data between devices.
Router
A type of computer that forwards data across a network
Binary
A way of representing information using only two options.
ASCII is a character-encoding scheme that uses a numeric value to represent each character. For example, the uppercase letter "G" is represented by the decimal (base 10) value 71. A partial list of characters and their corresponding ASCII values are shown in the table below. ASCII characters can also be represented by binary numbers. According to ASCII character encoding, which of the following letters is represented by the 8-bit binary value: 0100 0010
ASCII Character: B
A middle school is expanding to open a high school next year, doubling the total number of students. The school keeps a database in which each student's unique ID number is stored as an 8 bit number called studentID. Before the arrival of the new students almost every 8 bit number has already been assigned to a student. Of the options provided below, which is the smallest change to the way studentID is represented necessary to ensure each incoming student receives a unique ID?
Add a bit to studentID to double the number of IDs that the database can represent.
ASCII
American Standard Code for Information Interchange; the universally recognized raw text format that any computer can understand
What is a Distributed Denial of Service (DDoS) attack?
An attempt to compromise a single target by flooding it with requests from multiple systems.
URL
An easy-to-remember address for calling a web page (like www.code.org).
Choose the two correct definitions.
Bandwidth: a measure of bit rate - the amount of data (measured in bits) that can be sent in a fixed amount of time. Latency: the time elapsed between the transmission and the receipt of a request.
The figure represents a network of physically linked computers labeled A through F. A line between two computers indicates that the computers can communicate directly with each other. Any information sent between two computers that are not directly connected must go through at least one other computer. The weight or cost of sending information from one computer to another is indicated by the number above the line. For example, information can be sent directly between computers A, and B and will cost 5. Information sent between computers A and D must go through either computer C (with total cost 5), or through computer B (with total cost 8)Computer A sends a packet intended to reach computer F. Along its path it arrives at Computer C. Which computer should Computer C forward the packet to in order to use the most cost effective path?
Computer D
Select the answer that lists the units of bytes in ascending order (from smallest to largest)
kilobyte, gigabyte, terabyte
DDoS Attack
Distributed Denial of Service Attack. Typically a virus installed on many computers (thousands) activate at the same time and flood a target with traffic to the point the server becomes overwhelmed.
An artist makes an RGB raster image in which each pixel color is encoded with 12-bits --- 4 bits each for red, green and blue.Which of the following correctly shows the hexadecimal value for Red as a 12-bit representation.
F00
The various protocols in use on the internet are said to operate in layers in which the protocol(s) at each layer solve one problem related to networked communication, and higher layers are built on top of, and rely on, the lower layers to do their jobs.From the list provided choose the two (2) answers that correctly describe which internet protocol relies on the other. For example: if protocol A relies on protocol B, it means that A is a higher level protocol than B, and thus protocol B must exist and work properly in order for protocol A to do its jobs
HTTP relies on TCP/IP DNS relies on TCP/IP
HTTP is considered to be a high level protocol because:
HTTP requests make use of abstractions provided by lower level protocols.
private key
In an asymmetric encryption scheme the decryption key is kept private and never shared, so only the intended recipient has the ability to decrypt a message that has been encrypted with a public key.
How does a computer resolve a domain name into an IP address?
It asks a DNS server for the corresponding IP address
What is the best explanation for why digital data is represented in computers in binary?
It's easier, cheaper, and more reliable to build machines and devices that only have to distinguish between binary states.
To uncompress the data back into its original binary state, you simply reverse the process. This technique is an example of what type of compression?
Lossless compression
The colors of the pixels in a digital image are often represented by red, green, and blue values between 0 and 255 (an RGB triplet). A photographer is manipulating a digital image to lighten it because all of the RGB values in the image are less than 100, making it very dark. He does this by adding 20 to the R, G, and B values of each pixel, then overwriting the original image. What type of transformation is the photographer using on the digital image?
Lossless transformation
In very broad terms the MP3 audio compression algorithm identifies frequencies and volume levels - low and high - that are outside the range of human hearing and removes the data representing these frequencies from the original. This technique results in a smaller audio file that sounds exactly the same to the human ear.This technique is an example of what type of compression?
Lossy compression
Which of the following BEST describes how protocols on the Internet (e.g. IP, TCP, HTTP) make use of abstraction to accomplish their respective purposes?
Low level protocols can provide functionality to high level protocols without revealing the details of how this is accomplished
Why is the Vigenere cipher hard to crack? (select 2)
One cannot solve using frequency analysis directly. .The key length is variable and potentially very long
Which of the following statements best describes the properties of public key encryption?
Public key encryption is an encryption method which relies on separate keys for encrypting and decrypting information.
Which of the following is the most accurate statement about using search trends as predictors of future events?
Search trends are imperfect predictors of future events that may not fully represent society at large.
Packets
Small chunks of information that have been carefully formed from larger chunks of information.
Number systems with different bases such as binary (base-2) and decimal (base-10) are all used to view and represent digital data. Which of the following is NOT true about representing digital data?
Some large numbers cannot be represented in binary and can only be represented in decimal.
A coffee shop is considering accepting orders and payments through their phone app and have decided to use public key encryption to encrypt their customers' credit card information. Is this a secure form of payment?
Yes, public key encryption is built upon computationally hard problems that even powerful computers cannot easily solve.
Fill in the blank of the following statement: "______ encryption is a method of encryption involving one key for both encryption and decryption."
Symmetric
Which of the following is NOT true about TCP/IP packets?
TCP guarantees that no packets are ever dropped
A programmer is writing a system that is intended to be able to store large amounts of personal data. As the programmer develops the data system, which of the following is LEAST likely to impact the programmer's choices in designing the structure of the system?
The frequency of a particular item occurring in a data set.
What is the "key" to a Caesar Cipher that someone needs to know (or discover) to decrypt the message?
The number of characters to shift each letter in the alphabet.
Which of the following is a true statement about data compression?
There are trade-offs involved in choosing a compression technique for storing and transmitting data.
When a computer scientist uses the term "Big Data" what do they typically mean?
There is enough data that traditional data processing applications are inadequate.
Latency
Time it takes for a bit to travel from its sender to its receiver.
Bandwidth
Transmission capacity measure by bit rate
which of the following is true about lossy and lossless compression?
lossless compression will allow a file to be compressed into a smaller form, but will not sacrifice the information needed to put it back together in its entirely
Under which of the following conditions is it most beneficial to use a heuristic approach to solve a problem?
When the problem cannot be solved in a reasonable time and an approximate solution is acceptable
Cracking encryption
When you attempt to decode a secret message without knowing all the specifics of the cipher, you are trying to "crack" the encryption.
A school starts tracking which websites each computer in the school is visiting by monitoring the packets leaving the school. A sample of the information they have collected appears below: IP Address Time URL... ... ...1.1.1.1 11:05:23.22 example.com 1.5.1.8 11:05:29.71 news.com 1.1.5.1 11:06:13.48 sports.com 1.5.1.8 11:08:09.95 example.com... .. 1.1.5.1 17:04:29.20 news.com Which of the following is MOST likely to be answerable using all the data collected by this monitoring?
Which websites are most frequently visited before and after school hours from a school computer
private key encryption
it uses an asymmetric encryption scheme in which the encryption key is made private
Which of the following scenarios is most characteristic of a phishing attack.
You get an email from the IT support desk that asks you to send a reply email with your username and password to verify your account
Computationally Hard
a "hard' problem for a computer is one in which it cannot arrive at a solution in a reasonable amount of time.
Big Data
a broad term for datasets so large or complex that traditional data processing applications are inadequate.
modulo
a mathematical operation that returns the remainder after integer division. Example: 7 MOD 4 = 3
Moore's Law
a predication made by Gordon Moore in 1965 that computing power will double every 1.5-2 years, it has remained more or less true ever since.
Encryption
a process of encoding messages to keep them secret, so only "authorized" parties can read it.
Decryption
a process that reverses encryption, taking a secret message and reproducing the original plain text
Virus
a program that runs on a computer to do something the owner of the computer does not intend.
Abstraction
a simplified representation of something more complex. Abstractions allow you to hide details to help you manage complexity, focus on relevant concepts, and reason about problems at a higher level.
Caesar Cipher
a technique for encryption that shifts the alphabet by some number of characters
Phishing Scam
a thief trying to trick you into sending them sensitive information. Typically these include emails about system updates asking you send your username and password, social security number or other things.
According to the domain name system (DNS), which of the following is a subdomain of the domain example.com?
about.example.com
Random Substitution Cipher
an encryption technique that maps each letter of the alphabet to a randomly chosen other letters of the alphabet.
IETF
develops and promotes voluntary Internet standards and protocols, in particular the standards that comprise the Internet protocol suite (TCP/IP).
request for comments
formal document drafted by the IETF that describes the specifications for a particular technology
Network Redundancy
having multiple backups to ensure reliability during cases of high usage or failure
A base-16 number system that uses sixteen distinct symbols 0-9 and A-F to represent numbers from 0 to 15.
hexadecimal
Which of the following is the most accurate description of what is known as the "digital divide".The digital divide is about how...
people's access to computing and the Internet differs based on socioeconomic or geographic characteristics.
TCP
provides reliable, ordered and error checked delivery of a stream of packets in the internet
Firewall
software that runs on servers (often routers) that only allows traffic through according to some set of security rules.
a photographer has a shot session using RAW format. the client wishes to preview the photo shoot and requests that a series of photos be sent via mail. the files are too large for most email servers and must be compressed in order to be emailed. which of the following is correct about a compression of the files if the client wants to see the best quality photos?
the file must be compressed using a lossless compression
cipher
the generic term for a technique (or algorithm) that performs encryption
consider the following algorithm for manipulating the individual pixels of a digital RGB image of a panda bear surrounded by dense green jungle foliage. Algorithm: for each pixel, swap the value in the green and blue channels, leaving red channel alone.
the panda's fur will appear black and white, but the foliage will appear to be tinted blue
Net Nuetrality
the principle that all Internet traffic should be treated equally by Internet Service Providers.
HTTP
the protocol used for transmitting web pages over the internet
DNS
this system translates domain names to IP addresses
Asymetric Encryption
used in public key encryption, it is scheme in which the key to encrypt data is different from the key to decrypt
antivirus software
usually keeps big lists of known viruses and scans your computer looking for the virus programs in order to get rid of them.
