10.1 Intro to Cryptography Flashcards
Define cryptography
Cryptography is the art and science of keeping information secure through the use of mathematical concepts and techniques.
Define:
Plaintext
Information in human-readable form.
Define:
Ciphertext
Plaintext message that has been encrypted into an unreadable form.
Define:
Encryption
Process of converting plaintext to ciphertext.
Define:
Decryption
Process of converting ciphertext to plaintext.
Define:
Cipher
Method of performing encryption or decryption.
Define:
Key
Parameter specifying how plaintext is converted to ciphertext and vice versa.
Define:
Caesar Cipher
Type of cipher that shifts the letters in the alphabet by a fixed number.
Define:
Enigma cipher
Type of cipher used by Germany in World War II to encrypt messages.
What is ASCII stand for and what is it?
ASCII stands for the American Standard Code for Information Interchange. It’s a code for representing English characters as numbers, assigned from 0 to 127
What’s the goal of encoding?
The goal of encoding isn’t to keep a message secret, but to transform data to be used by another system.
True or False
Encoding, unlike encryption, does not use a key.
True
True or False
Encoding is often used to transform binary data into digital text data, where encryption commonly takes place.
False
Encoding is often used to transform digital text data into binary data, where encryption commonly takes place.
Goals of Cryptography
What is the P.A.I.N model.
Privacy
Authentication
Integrity
Non-repudiation
________ keeps data secure from unauthorized parties.
Privacy keeps data secure from unauthorized parties.
________ is used to confirm the identities of the sender and receiver of data.
Authentication is used to confirm the identities of the sender and receiver of data.
________ ensures a message isn’t altered between when it’s sent and when it’s received.
Integrity ensures a message isn’t altered between when it’s sent and when it’s received.
________ prevents the original sender from denying they were the sender.
Non-repudiation prevents the original sender from denying they were the sender.
_________ apply their algorithm one bit (character) at a time.
Stream ciphers apply their algorithm one bit (character) at a time.
One prominent stream cipher is the ___________
One prominent stream cipher is the substitution cipher.
True or False
Substitution ciphers substitute out old values for new values of input message.
True
_________ apply their algorithm to chunks of characters.
Block ciphers apply their algorithm to chunks of characters.
One prominent block cipher is the _____________
One prominent block cipher is the transposition cipher.
- Break the message into blocks of three characters.
- Replace the first, second, and third character of each block with the third , first, and second character.
- Combine rearranged text.
True or False
Ciphers use mathematical formulas known as algorithms to encrypt and decrypt data.
True
The main cipher categories are _____ and ______ ciphers.
The main cipher categories are block and stream ciphers.
A type of stream cipher is the _________ cipher , and a type of block cipher is the _________ cipher.
A type of stream cipher is the substitution cipher, and a type of block cipher is the transposition cipher.
True or False
Substitution ciphers replace each character with a completely different character.
True
Each algorithm has a possible range of numbers that can be used as a key, known as a _______.
Each algorithm has a possible range of numbers that can be used as a key, known as a key space.
For modern cryptography, key space is defined by the number of binary bits used in the key, known as _______.
For modern cryptography, key space is defined by the number of binary bits used in the key, known as bit size.
What is the formula for bit size?
Key space = 2 (to the power of bit size)
True or False
Modern symmetric key algorithms use algorithms that are secure and fast.
True
What are the widely known symmetric key algorithms?
- Data Encryption Standard (DES),
- Triple DES (3DES)
- Advanced Encryption Standard (AES)
What does DES stand for?
Data Encryption Standard (DES) is a 56-bit key published by the United States government in 1977.
