Cyryptograph Flashcards
What is cryptography?
The science of protecting the confidentiality and integrity of data.
What is encryption?
The process of converting plaintext (readable data) into ciphertext (encoded data).
What is decryption?
The process of converting ciphertext back into plaintext using a key.
What is the Caesar cipher?
A substitution cipher that shifts each letter by a fixed number of places in the alphabet.
What is ROT13?
A Caesar cipher variant that shifts letters by 13 places.
What was the Jefferson Disk?
A mechanical substitution cipher invented by Thomas Jefferson in 1795, using 36 rotating disks.
What was the Enigma Machine?
A German-made cipher device (1923) that used electrical currents to encode messages.
What is the key idea behind Kerckhoffs’s second principle?
Even if an adversary knows the encryption algorithm, the system should remain secure as long as they do not have the key.
What are the six principles of Kerckhoffs’s cryptographic design?
The system must be mathematically undecipherable.
The system must not require secrecy (only the key needs protection).
Keys must be easy to communicate and change.
The system should be compatible with telegraph communication.
The system must be portable and usable by one person.
The system must be simple to use.
How does a keyword cipher work?
The alphabet is rearranged using a keyword before performing substitution.
Why is a one-time pad considered unbreakable?
It uses a random key that is as long as the message and is used only once.
What is another name for a one-time pad?
The Vernam cipher.
What is symmetric cryptography?
A private key cryptography system where one key is used for both encryption and decryption.
What is a block cipher?
Encrypts data in fixed-size blocks (e.g., 64-bit or 128-bit blocks).
What is a stream cipher?
Encrypts data one bit at a time, making it more efficient for continuous data streams.
What are three major symmetric key algorithms?
DES (Data Encryption Standard) – 56-bit key, weak by today’s standards.
3DES (Triple DES) – Encrypts data three times to improve security.
AES (Advanced Encryption Standard) – Uses 128-bit, 192-bit, or 256-bit keys.
What is asymmetric cryptography?
Uses a public key for encryption and a private key for decryption.
What is RSA commonly used for?
SSL/TLS encryption and secure digital signatures.
What does ECC stand for, and why is it useful?
Elliptic Curve Cryptography (ECC) – It provides strong encryption with smaller key sizes.
What is ECDSA?
Elliptic Curve Digital Signature Algorithm, used for secure digital signatures.
What is the Digital Signature Standard (DSS)?
A U.S. government standard for digital signatures.
What is PGP (Pretty Good Privacy)?
A program that provides email encryption and digital signatures.
What does TLS (Transport Layer Security) do?
It encrypts internet communications (e.g., HTTPS, email, VPNs).
What is a hash function?
A one-way cryptographic function that converts plaintext into a fixed-length hash value.
What is the purpose of a digital signature?
To verify authenticity and integrity and provide nonrepudiation.
How does a digital signature work?
A hash of the message is generated.
The hash is encrypted using the sender’s private key.
The receiver decrypts the hash using the sender’s public key and compares it to a freshly computed hash.
What is the purpose of a digital certificate?
To link a public key to an individual, proving the key’s ownership.
What entity signs and verifies certificates?
A Certificate Authority (CA).
What are the two main authorities of Public Key Infrastructure (PKI)?
Certificate Authorities (CA) – Issue and verify digital certificates.
Registration Authorities (RA) – Verify the identity of individuals before issuing certificates.
What is data at rest?
Stored data on storage devices like hard drives or USBs.
How is data at rest protected?
Encryption (e.g., BitLocker, VeraCrypt) and physical security (locks, cameras).
What is data in motion?
Data being transferred across networks (e.g., emails, file transfers).
How is data in motion protected?
SSL/TLS encryption, VPNs, and IPsec.
What network security protocols protect data in motion?
SSL/TLS (Secure Sockets Layer / Transport Layer Security).
IPsec (Internet Protocol Security) for VPNs.
POP3/IMAP (Encrypted email retrieval protocols).
What is data in use?
Data actively being accessed or processed in memory.
Why is protecting data in use challenging?
Encryption is difficult while the data is being processed in memory.
