unit 6 APCSP

abstraction layer

The Internet is organized into several of these which are controlled by various protocols. From the bottom up, we have the link layer (Ethernet protocol), the Internet layer (IP), transport layer (TCP), and application layer (HTTP).

asymmetric cipher

A cipher in which separate but related keys are used for encryption and decryption.

bandwidth

the rate at which data is downloaded or uploaded in a network

biometrics

using unique physical characteristics such as finger prints, face recognition, etc. for identification

brute force attack

An attempt to try every possible encryption key to break a secret message.

certificate authority

An entity that issues digital certificates.

cipher

A system for creating secret messages.

ciphertext

unreadable, secret message.

client

A computer or software application that requests services from a server located on the internet -- e.g., a Web browser is an example of a client.

computer bug

An informal term for error in computer hardware or software -- the term was coined by Grace Hopper.

computing system

A group of computing devices and programs working together for a common purpose.

cryptography

The art and science of writing secret messages. 'secret writing'

debugging

The process of removing errors from computer hardware or software.

decryption

The process of using a secret key to convert ciphertext into plaintext.

diffie-hellman

An algorithm used to establish a shared secret between two parties. It is primarily used to exchange a symmetric cryptographic key among two parties, Alice and Bob, who wish to communicate securely.

digital certificate

A data packet that certifies the holder of a public key.

digital divide

the gap between those who have access to the Internet and computers and those who do not, usually affected by socioeconomic, geographic, or demographic characteristics.

DNS

An Internet service that translates domain names into IP addresses.

domain name

A hierarchical name (such as trincoll.edu) that identifies a domain and an institution on the Internet. Top levels include com, edu, gov.

encryption

The process of using a secret key to convert plaintext into ciphertext.

encryption key

A piece of secret data used in by encryption and decryption algorithms.

ethernet

A network that uses wires to connect computers.

fault-tolerant

The capability of a system to continue operating properly in the event of the failure of one or more of its components.

firewalls

barriers that protect a network from unauthorized access

frequency analysis

This is performed by counting the occurrence of the letters in an encrypted message in an effort to discover patterns that might reveal the encryption key.

function

A procedure that computes and returns a value.

host

A computer that's connected directly to the Internet -- often a computer that provides certain services or resources.

HTML

A language for formatting Web pages.

HTTP

The set of rules that governs the WWW application.

https

A protocol for secure (trusted, encrypted) communication over the Internet.

Internet Service Provider

A company that provides customers with Internet access.

intractable

A computational problem is labeled this if the only known way to solve the problem depends on an exponential algorithm.

IP Address

A unique string of numbers separated by periods that identifies each computer using the Internet Protocol to communicate over a network.

IPv4

An older 32 bit IP address

IPv6

A newer 128 bit IP address which allows for many more devices to be addressed.

key exchange problem

The problem of sharing a secret key between Alice and Bob, without Eve, an eavesdropper, being able to intercept it.

keylogger

a program to record every keystroke made by a computer user.

LAN

A network that connects computers within a school or home.

latency

a measure of the time it takes for a piece of data to reach its destination

local variables

Variables that are declared and exist only inside a procedure or function (this is called their scope).

malware

Software intended to damage a computing system or to take partial control over its operation.

malware scanning software

Software that helps to protect a computing system against malware infections.

modem

A device that connects a computer to an Internet Service Provider (ISP).

multi-factor authentication (MFA)

users are asked to present several separate pieces of evidence involving knowledge (something they know like a password), possession (something they have like a texted code), and/or inherence (something they are like biometrics).

network

A group of two or more computers that are linked together.

one time pad

An example of perfect (unbreakable) encryption, which is achieved by using, only once, a random polyalphabetic key that is as long the message itself.

packet

A collection of data used by the TCP/IP protocol to transmit data across the Internet. Each packet contains routing data as well as the content of the message.

packet sniffer

Software used by network administrators to monitor data being transmitted over a network. In the wrong hands, it can be used to steal email messages and other information.

packet switching

The method by which information is transmitted through the Internet. Information is broken into packets and each packet is routed independently from source to destination.

phishing

a technique that is used to trick a user into providing personal information usually through email.

ping

A networking utility used by network administrators to test the reachability of a host on the Internet.

plaintext

An unencrypted, readable message.

polyalphabetic substitution

In this system, multiple alphabets are used to encrypt a single message.

protocol

A system of rules that govern the behavior of some system.

public key cryptography

A cryptographic system that uses two keys -- a public key known to everyone and a private or secret key known only to the recipient of the message. When Bob wants to send a secure message to Alice, he uses Alice's public key to encrypt the message. Alice then uses her private key to decrypt it.

ransomware

malware that encrypts and locks computer systems until a ransom is paid.

rogue access point

Gives unauthorized access to secure networks.

router

A device that transmits data between two different networks.

routing

The process of finding a path from sender to receiver.

RSA

A cryptosystem for public-key encryption, and is widely used for securing sensitive data, particularly when being sent over an insecure network such as the Internet.

run-time error

A mistake in the program that occurs during the execution of a program.

scalability

The capacity for the system to change in size and scale to meet new demands.

semantic error

An error in which the program is not working as it is designed to work.

server

A host that provides some kind of service -- e.g., Google's Gmail service.

SMTP/POP

Sets of rules that govern the email servcies.

SSL

A protocol for establishing an encrypted link between a web server and a browser.

strong password

A series of characters that is easy for a user to remember, but would be difficult for someone else to guess based on knowledge of that user.

substitution cipher

A cipher in which letters from a ciphertext alphabet are substituted for the letters in a plaintext message in a systematic way.

symmetric cipher

A cipher in which a single key is used for both encryption and decryption.

syntax error

An error that results from a violation of the programming language grammatical rules.

traceroute

A networking utility used to trace the route and measure delays of packets moving through the Internet.

transposition cipher

In this cipher, letters in the plaintext are rearraged without substitution.

Trojan horse

a malicious program that disguises itself as a useful program that unsuspecting users download.

trust model

The use of a trusted third party to verify the trustworthiness of a digital certificate.

URI

WWW identifier that uniquely identifies a resource on the WWW -- e.g., http://host.com'.

virus

a malicious program that can copy itself and gain access to a computer in an unauthorized way

WAN

A network that connects devices over a broad geographic region -- e.g., a telephone network.

wifi

A network that uses radio waves to connect devices (computers, smart phones, printers).

World Wide Web

An Internet application that is based on the HTTP protocol.

worm

a malicious program that spreads by itself through networks of computers