Unit 4 test

The Caesar Cipher has 25 different shifts to try. How many possibilities are there to try in a random substitution cipher?

26 × 25 × 24 ×···× 3 × 2 x 1

Compute: 15 MOD 4

3

What is 20 MOD 15?

5

Approximately how much bigger (how many more bytes) is a megabyte than a kilobyte? A. 1,000 times bigger B. 100,000 times bigger C. 1,000,000 times bigger D. 1,000,000,000 times bigger

A. 1,000 times bigger

usually keeps big lists of known viruses and scans your computer looking for the virus programs in order to get rid of them

Antivirus Software

Historically it has been observed that computer processing speeds tend to double every two years. This is known as: A: Boolean's Conjecture B: Moore's Law C: The "Big Data Effect" D: Powers of 2 Principle

B: Moore's Law

a "hard' problem for a computer is one in which it cannot arrive at a solution in a reasonable amount of time.

Computationally Hard

When you attempt to decode a secret message without knowing all the specifics of the cipher, you are trying to crack the encryption.

Cracking encryption

What is the difference is between "cracking" a code and "decrypting" a message?

Cracking is when you attempt to decode a secret message without knowing all the specifics of the cipher and decryption is when you already know the key and are trying to reverse the process of encryption.

A process of encoding messages to keep them secret, so only authorized parties can read it.

Encryption

a process of encoding messages to keep them secret, so only "authorized" parties can read it.

Encryption

software that runs on servers (often routers) that only allows traffic through according to some set of security rules.

Firewall

a value that can be used to encrypt a message. However, only when combined with a mathematically-related private key, can the message be decrypted.

Public Key

an encoding technique that maps each letter of the alphabet randomly to different letters or characters.

Random Substitution Cipher

In symmetric encryption the same key is used to encrypt and decrypt a message. In asymmetric encryption different keys are used to encrypt and decrypt. Give at least one reason why asymmetric encryption is useful

The public key is public but the decryption key is private, and with two different keys, it will be more difficult to crack the asymmetric encryption.

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.

a method of encrypting text by applying a series of Caesar ciphers based on the letters of a keyword.

Vigenère cipher

Malware that replicates itself is called

Virus

a program that runs on a computer to do something the owner of the computer does not intend.

Virus

Translate the following using a Caesar cipher with a shift of 3 places: CS IS COOL

ZP FP ZLLI

Bob adding beans to the cup

example: encrypting a message

The number of beans Alice chooses to put in the cup initially

example: private key

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? A. 2 times as many values can be represented. B. 32 times as many values can be represented. C. 2^32 times as many values can be represented. D. 32^2 times as many values can be represented.

C. 2^32 times as many values can be represented.

a technique for encryption that shifts the alphabet by some number of characters.

Caesar's Cipher

When a computer scientist uses the term "Big Data" what do they typically mean? A: That a dataset is larger than 5TB which is the common "Big Data" threshold. B: That there is so much data it's virtually impossible to process. C: There is enough data that traditional data processing applications are inadequate. D: It implies that the findings from the data are potentially hugely important for society.

C: There is enough data that traditional data

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.

DDoS Attack

Alice dumping beans out of the cup and counting off her original number

Decrypting a message

List 3 characteristics of the ideal encryption scheme.

1. easy to encode 2. easy to decode 3. difficult to crack

What is 13 MOD 17?

13

Why is the Vigenere cipher hard to crack?

>one cannot solve using frequency analysis directly >the key length is variable and potentially very long

Fill in the blank of the following statement: "______ encryption is a method of encryption involving one key for both encryption and decryption." A. Symmetric B. Asymmetric C. Public key D. SSL

A

Which of the following are true statements about digital certificates in Web browsers? I. Digital certificates are used to verify the ownership of encrypted keys used in secured communication. II. Digital certificates are used to verify that the connection to a Web site is fault tolerant. (A) I only (B) II only (C) I and II (D) Neither I nor II

A

Pick the two expressions involving the Modulo operation that compute to the exact same value (choose 2) A. 9 MOD 8 B. 1 MOD 16 C. 52 MOD 32 D. 9 MOD 64

A & B

the generic term for a technique (or algorithm) that performs encryption

Cipher

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.

Phishing Scam

the complementary key to a public key that is used to decrypt a message.

Private Key

It is the scheme in which the key to encrypt data is different from the key to decrypt.

Asymmetric Encryption

a broad term for datasets so large or complex that traditional data processing applications are inadequate.

Big Data

Choose the answer that is NOT a feature of Public Key Cryptography: A. A key for decrypting is never made public B. Using public key guarantees that only the intended recipient can decrypt the message C. A Public Key database ensures 3rd party accountability of security D. Allows secure communication without establishing a *shared* encryption key ahead of time.

C

The process that reverses encryption, taking a secret message and reproducing the original text

Decryption

Which of the following statements best describes the properties of public key encryption? A. Public key encryption is an encryption method which relies on separate keys for encrypting and decrypting information. B. Public key encryption is a highly secure encryption scheme that in which a single shared key is used by both the sender and receiver of the message. C. Public key encryption makes use of certain types of problems which are easier for humans to solve than computers. D. Public key encryption makes use of mathematical problems which no algorithm can be used to solve.

A

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? A. Lossless transformation B. Lossy transformation C. Multiband transformation D. Chrome Sampling transformation

A. Lossless transformation

A raw digital sound file samples a sound wave at some interval and measures the height of the wave at each point. Thus, raw sound is recorded as a list of numbers. 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? A. Lossy compression B. Lossless compression C. Fast Fourier Transform compression D. Tailored compression

A. Lossy compression

a type of cryptographic based on algorithms that require two keys -- one of which is secret (or private) and one of which is public (freely known to others).

Asymmetric encryption

Which of the following is the most accurate description of what is known as the "digital divide". The digital divide is about how... A) ...people's access to computing and digital technology increases over time through a process of dividing and growing quickly - it is often likened to the biological processes of cell growth B) ...people's access to computing and the Internet differs based on socioeconomic or geographic characteristics. C) ...people's access to computing technology is affected by the fact that newer devices that use new protocols makes it more difficult for them to communicate with older devices and technology D) ..the amount of data on the Internet is growing so fast that the amount computing power and time we have to process it is lagging behind

B

Which of the following scenarios is most characteristic of a phishing attack. A. You accidentally run a piece of code that automatically spreads from one computer to another, exploiting a common vulnerability B. 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 C. You get an unwanted email trying to sell you a low quality product or service that seems "fishy." D. You accidentally install a piece of software that monitors your activity to steal personal information like your passwords, date of birth, social security number, etc.

B

Why are computers better than humans at breaking encryptions such as the Vigenere? A.) Computers are smarter than humans. B.) Computers are faster than humans. C.) The Vigenere was originally designed by a computer. D.) They are not; humans are better as breaking Vigenere encryptions than computers.

B

This question refers to the same data from the High School Survey about college plans from the previous question. Amara plans to use the survey data to create a visualization and short write up about students' plan for college, but first she wants to learn more about how the survey was conducted. Of the following things she might learn about the survey, which are the most likely sources of bias in the results based on how it was collected? (2 answers) A) She learns that the survey administrators only asked a representative sample of students, rather than every student in each state. B) She learns that responses were collected only by mobile app. C) She learns that the survey was only available to students who scored at the top 10% on the PSAT. D) She learns the survey was available to complete in both digital and paper form.

B C

What is the "key" to a Caesar Cipher that someone needs to know to decrypt the message? a) A secret word only know by Caesar. b) The number of characters to shift each letter in the alphabet. c) The letter that occurs most often in the encrypted message. d) The day of the month that the encrypted message was sent.

B) Number of characters to shift each letter in the alphabet

In symmetric encryption the same key is used to encrypt and decrypt a message. In asymmetric encryption different keys are used to encrypt and decrypt. Give at least one reason why asymmetric encryption is useful

Because asymmetric encryption is using different keys, it is harder to decode.

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? A. No, public key encryption allows the credit card information to be read by the public. B. No, the internet protocols are open standards and thus everything sent over the internet is sent "in the clear". C. Yes, public key encryption is built upon computationally hard problems that even powerful computers cannot easily solve. D. Yes, public key encryption is secure because it transmits credit card information in binary.

C

A programmer completes the user manual for a video game she has developed and realizes she has reversed the roles of goats and sheep throughout the text. Consider the programmer's goal of changing all occurrences of "goats" to "sheep" and all occurrences of "sheep" to "goats." The programmer will use the fact that the word "foxes" does not appear anywhere in the original text. Which of the following algorithms can be used to accomplish the programmer's goal? (A) First, change all occurrences of "goats" to "sheep." then, change all occurrences of "sheep" to "goats." (B) First, change all occurrences of "goats" to "sheep." then, change all occurrences of "sheep" to "goats." Last, change all occurrences of "foxes" to "sheep." (C) First, change all occurrences of "goats" to "foxes." then, change all occurrences of "sheep" to "goats." Last, change all occurrences of "foxes" to "sheep." (D) First, change all occurrences of "goats" to "foxes." then, change all occurrences of "foxes" to "sheep." Last, change all occurrences of "sheep" to "goats."

C

Under which of the following conditions is it most beneficial to use a heuristic approach to solve a problem? (A) When the problem can be solved in a reasonable time and an approximate solution is acceptable (B) When the problem can be solved in a reasonable time and an exact solution is needed (C) When the problem cannot be solved in a reasonable time and an approximate solution is acceptable (D) When the problem cannot be solved in a reasonable time and an exact solution is needed

C

Which of the following most accurately describes Moore's Law: A. Moore's Law describes a relationship of boolean logic statements involving AND and OR B. Moore's Law is the principle that one should assume that any traffic on the Internet is insecure C. Moore's Law is the observation that computing power tends to double every two years D. Moore's Law explains why cracking modern cryptography is a "computationally hard" problem

C

Choose the answer that is NOT a feature of Public Key Cryptography: A. A key for decrypting is never made public B. Using public key guarantees that only the intended recipient can decrypt the message C. A Public Key database ensures 3rd party accountability of security D. Allows secure communication without establishing a shared encryption key ahead of time.

C. A Public Key database ensures 3rd party NOTE: Public-key cryptography is any cryptographic system that uses pairs of keys. Public keys may be distributed and paired with private keys which are known only to the owner. Since the public and private keys are given by the owner, no third parties should be held accountable for the security of the information.

All of the below items are characteristics of : 1. Easy/ Fast to encode 2. Decoding returns the exact data that word encoded originally 3. Encoded message is easy to transmit or communicate

Caesar Cipher

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? A. Maintaining privacy of the information stored in the data set. B. Scalability of the system. C. Structuring the metadata of the information for analysis. D. The frequency of a particular item occurring in a data set.

D

Which of the following is a true statement about data compression? A. Data compression is only useful for files being transmitted over the Internet. B. Regardless of the compression technique used, once a data file is compressed, it cannot be restored to its original state. C. Sending a compressed version of a file ensures that the contents of the file cannot be intercepted by an unauthorized user. D. There are trade-offs involved in choosing a compression technique for storing and transmitting data.

D. There are trade-offs involved in choosing a compression technique for storing and transmitting data.

Select the answer that lists the units of bytes in ascending order (from smallest to largest) A. gigabyte, megabyte, terabyte B. megabyte, terabyte, kilobyte C. gigabyte, terabyte, megabyte D. kilobyte, gigabyte, terabyte

D. kilobyte, gigabyte, terabyte

Which of the following statements is the LEAST TRUE about personal data that technology companies potentially collect about their users? A: companies frequently offer services free of charge in exchange for access to data about their users B: personal data about users may be saved by a company permanently, never to be deleted C: companies can sell the personal information of users to advertisers or other businesses D: companies are required by law to give users options to personalize what data they collect about them

D: Companies are required by law to give users options to personalize what data they collect about them

a process that reverses encryption, taking a secret message and reproducing the original plain text

Decryption

In what situations on the Internet do you typically want to keep information secret? From whom do you want to keep it to be secret? How do you think your privacy is maintained on the Internet now?

I want to keep information secret when I go shopping online. I would want to keep this information from someone who wants to steal my identity. My privacy is maintained by encryption.

Why might it actually be a good thing that encryption algorithms are freely shared, so that anyone who wishes can try to crack them?

If the security of an encryption technique relies solely on the method remaining a secret, it actually may not be that secure. Ideally, a method will be so secure that even if you know which technique was used, it is difficult or impossible to crack the message. By making encryption techniques public, we open them up to being tested by anyone who wishes to ensure there are no clever ways of cracking the encryption.

the name of the mathematical operation. Modulo gives the remainder from dividing two numbers.

Modulo

the observation that computing power roughly doubles every two years.

Moore's Law

A business/corporate term for a one-page document that summarizes a large issue, topic or plan. The purpose is to distill and highlight the most important pieces of information in a digestible manner so that the reader can be quickly acquainted with the relevant details of the "big picture."

One-Pager

Describe to a person who knows nothing about encryption why public key encryption is secure and is hard to crack.

Public key encryption is hard to crack because it can only be decrypted when combined with a mathematically-related private key.

Secure Sockets layer / Transport Layer Security - An encryption layer of HTTP that uses public key cryptography to establish a secure connection.

SSL/TLS

What is the "key" to the Caesar Cipher that someone need to know to decrypt a message?

The number of characters to shift each letter in the alphabet

The opening pages of Blown to Bits, Chapter 5, discuss a move the government made to try to control encryption in the aftermath of the terrorist attacks of September 11, 2001, but then dropped. Additionally, during the 1990s, the US Government was pressuring the computer industry to be allowed to have a "back door" to decryption. Why do you think they stopped urging for this?

This would weaken the public's trust in the Internet as an e-commerce vehicle. Any back door could probably be exploited by others. The government believed they could eventually break cryptography without a back door.

Using the Vigenere cipher, does the length of the key matter? For example, if one key is length 5 and another is 20, does one produce a "better" encrypted message than the other, or is it basically the same? Yes or no?

When using the Vigenere cipher, the longer the key the better the encrypted message. However, it is really only better if the key is composed of different letters rather than one letter combined. Therefore, a key that is long with multiple letters is a better key than one that is short because the letters of the plaintext are shifted different amounts with more shifts.

Why is the Vigenere cipher hard to crack? a) One cannot solve using frequency analysis directly. b) Long keys create exponential growth possibilities. c) The key is always secret to both the sender and receiver of the message. d) A Vigenère cipher relies upon an "alphabet shift" algorithm.

a. One cannot solve using frequency analysis directly. b. The key length is variable and potentially very long

What is a Distributed Denial of Service (DDoS) attack? A. A coordinated effort by a group to simultaneously attempt to gain entry to foreign government's servers or systems B. An effort by network engineers to focus all systems on catching a user or computer that has illegally gained access. C. An attempt to compromise a single target by flooding it with requests from multiple systems. D. An attempt to harass or extort all customers of one or more Internet Service Providers (ISPs).

c

An attempt to get a victim to submit sensitive data by imitating a legitimate authority

Phishing Scam

A sealed cup of beans that Alice puts on the table

example: public key