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Computer Security and Reliability
AP Computer Science Principles Unit 4 Vocab
Terms in this set (26)
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
A business/corporate term for a one-page document that summarizes a large issue, topic or plan
a technique for encryption that shifts the alphabet by some number of characters
the generic term for a technique (or algorithm) that performs 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 process that reverses encryption, taking a secret message and reproducing the original plain text
a process of encoding messages to keep them secret, so only "authorized" parties can read it
Random Substitution Cipher
an encryption technique that maps each letter of the alphabet to a randomly chosen other letters of the alphabet
a "hard' problem for a computer is one in which it cannot arrive at a solution in a reasonable amount of time
using an algorithm to undo the encryption. It's like using a key to unlock a lock. It's what the sender is expecting the intended recipient to do to recover the original message
is more like detective work - it's like trying to pick a lock - using various methods to try to figure out what the secret message is without having or knowing the decryption "key" ahead of time
The Internet is not inherently secure.
Packets traveling across the Internet move through many routers, each of which could be owned by different people or organizations.
So we should assume all information traveling across the Internet to be public, as if written on a postcard and sent through the mail.
The Vigenere Cipher
A well-chosen key makes a difference - there are certain keys that don't produce good results.
We're approaching much stronger encryption because we don't need to keep the encryption method a secret.
For example, if I told my enemy that I encrypted a message with the Vigenère cipher, my enemy would still have to do a virtually impossible amount of work to crack the code.
Even if I told my enemy the length of the key I used, as long as that length is sufficiently large, it would still leave my enemy basically randomly guessing the key. (Even for this simplified tool, if the key is 10 letters, then there are 26^10 possible keys, ~141 trillion.)
Understand the relationship between cryptographic keys and passwords.
A Key is an input to an encryption algorithm. A password is basically the same thing.
Understand why using longer passwords makes them harder to guess.
Longer passwords increase the number of possible keys making it Computationally hard to guess what the key is.
used in public key encryption, it is scheme in which the key to encrypt data is different from the key to decrypt
*is a big deal because without it modern ideas about security on the web would not be possible
a mathematical operation that returns the remainder after integer division. Example: 7 MOD 4 = 3
Public Key Encryption
Used prevalently on the web, it allows for secure messages to be sent between parties without having to agree on, or share, a secret key. It uses an asymmetric encryption scheme in which the encryption key is made public, but the decryption key is kept private.
Computationally hard problems
are problems for which the only known algorithm to solve them would take an unreasonable amount of time to run to completion. In cryptography this typically means have no avenue to crack a code besides exhaustively guessing every possible key
Use of the word "Key" is confusing
A "public key" is actually used more like a lock. Bob uses Alice's public key in combination with his private message to encrypt (or lock up) a new message that can be sent over public channels.
The physical analogy of lockboxes breaks down at some point because we're doing this locking and unlocking with mathematics.
Implementing cybersecurity has software, hardware, and human components.
Vulnerabilities in hardware and software can be compromised as part of an attack.
A large percentage of cybersecurity vulnerabilities are human-related, such as choosing bad passwords, (unintentionally) installing viruses, or giving personal information away.
Sockets layer/transport layer security (SSL/TLS)
An encryption layer of HTTP. When you see the little lock icon and https it means that you are visiting a website over HTTP but the data going back and forth bewtween you and the server is encrypted.
SSL (secure sockets layer) and TLS (transport layer security) use public key cryptography to establish a secure connection.
Cyber warfare and cyber crime have widespread and potentially devastating effects.
This is especially true in the case of warfare which (fortunately) we have not experienced much of on a global scale. But using cyber attacks to cripple basic infrastructure (power, water) and communication could be devastating.
Distributed denial of service attacks (DDoS)
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 - doing this can render web services like DNS, or routers, or certain websites useless and unresponsive.
Typically 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.
More sophisticated scams can make websites and email look very similar to the real thing.
Viruses / Antivirus software and firewalls
A virus is program that runs on a computer to do something the owner of the computer does not intend. Viruses can be used as a Bot Net to trigger a DDoS-style attack, or they can spy on your computer activity, such as capturing all the keystrokes you make at the computer, or websites you visit, etc.
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.
A "firewall" is simply software that runs on servers (often routers) that only allows traffic through according to some set of security rules.
THIS SET IS OFTEN IN FOLDERS WITH...
AP Computer Science Principles Unit 4
AP Computer Science Principles Vocab 1
AP Computer Science Principles Vocab 2
AP Computer Science Principles Vocab 3
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