Cryptography Flashcards
Symmetric vs. Asymmetric Encryption
Symmetric: Sender & receiver must know the same secret using privately held key
(100-1000x faster than asymmetric)
Ex: DES/3DES, IDEA, AES, Blowfish, Twofish, RC4/RC5/RC6
Asymmetric: Different keys are use to encrypt/decrypt the data
Ex: Diffie-Hellman, RSA, ECC
Encryption: Hybrid Implementation
Utilizes asymmetric encryption to securely transfer a private key that can then be used with symmetric encryption
Stream Cipher
Utilizes a keystream generator to encrypt data bit by bit using a mathematical XOR function to create the ciphertext
Bit-by-bit process
Block Cipher
Breaks the input into fixed-length blocks of data and performs the encryption on each block
Block ciphers are easier to implement through a software solution
DES & 3DES
Data Encryption Standard:
Encryption algorithm which breaks the input into 64-bit blocks and uses transposition and substitution to create ciphertext using an effective key strength of only 56-bits
(8 bits are used for parity)
Triple DES:
Encryption algorithm which uses three separate symmetric keys to encrypt, decrypt, then encrypt the plaintext into ciphertext in order to increase the strength of DES
IDEA
International Data Encryption Algorithm:
Symmetric block cipher which uses 64-bit blocks to encrypt plaintext into ciphertext
AES
Advanced Encryption Standard:
Symmetric block cipher that uses 128-bit, 192-bit, or 256-bit blocks and a matching encryption key size to encrypt plaintext into ciphertext
AES is the standard for encrypting sensitive U.S. Government data
Blowfish
Symmetric block cipher that uses 64-bit blocks and a variable length encryption key to encrypt plaintext into ciphertext
Twofish
Symmetric block cipher that replaced blowfish and uses 128-bit blocks and a 128-bit, 192-bit, or 256-bit encryption key to encrypt plaintext into ciphertext
RC (4, 5, 6)
Rivest Cipher 4:
Symmetric stream cipher using a variable key size from 40-bits to 2048- bits that is used in SSL and WEP
RC5:
Symmetric block cipher (key sizes up to 2048-bits)
RC6:
Symmetric block cipher introduced as replacement for DES (but AES won)
Public Key Cryptography
Asymmetric algorithms are also known as Public Key Cryptography
▪ Confidentiality
▪ Integrity
▪ Authentication
▪ Non-repudiation
Digital Signature
A hash digest of a message encrypted with the sender’s private key to let the recipient know the document was created and sent by the person claiming to have sent it
Diffie-Hellman
Used to conduct key exchanges and secure key distribution over an unsecured network
Diffie-Hellman is used for the establishment of a VPN tunnel using IPSec
RSA
Rivest, Shamir, & Adleman:
Asymmetric algorithm that relies on the mathematical difficulty of factoring large prime numbers
RSA is widely used for key exchange, encryption, and digital signatures
RSA can use key sizes of 1024-bits to 4096-bits
ECC
Elliptic Curve Cryptography:
Algorithm that is based upon the algebraic structure of elliptic curves over finite fields to define the keys
ECC with a 256-bit key is just as secure as RSA with a 2048-bit key
6 times more efficient than RSA
ECDH
Elliptic Curve Diffie-Hellman
ECDHE
Elliptic Curve Diffie-Hellman Ephemeral
ECDSA
Elliptic Curve Digital Signature Algorithm
ECC is most commonly used for mobile devices and low-power computing device
PGP
Pretty Good Privacy:
An encryption program used for signing, encrypting, and decrypting emails
The IDEA algorithm is used by PGP
Symmetric functions: 128-bit or higher keys
Asymmetric functions: 512-bit to 2048-bit key sizes
GPG
GNU Privacy Guard:
A newer and updated version of the PGP encryption suite that uses AES for its symmetric encryption functions
GPG has cross-platform availability
One-Time Pad
A stream cipher that encrypts plaintext information with a secret random key that is the same length as the plaintext input
(Not commonly used)
There are no such thing as truly random numbers in computers
PRNG
Pseudo-Random Number Generator:
A simulated random number stream generated by a computer that is used in cryptography, video games, and more
Steganography
The science and art of hiding messages within other messages
Steganography is a form of obfuscation, not encryption
Blockchain
A shared, immutable ledger for recording transactions, tracking assets and building trust
Most famous example of the blockchain is those used in cryptocurrencies
Public Ledger
A record-keeping system that maintains participants’ identities in secure and anonymous form, their respective cryptocurrency balances, and a record book of all the genuine transactions executed between network participants
A permissioned blockchain is used for business transactions and promotes new levels of trust and transparency using an immutable public ledger
Quantum Computing
A computer that uses quantum mechanics to generate and manipulate quantum bits (qubits) in order to access enormous processing powers
Quantum Communication
A communications network that relies on qubits made of photons (light) to send multiple combinations of 1s and 0s simultaneously which results in tamper resistant and extremely fast communications
Qubit
A quantum bit composed of electrons or photons that can represent numerous combinations of 1s and 0s at the same time through superposition
Cryptography is used to secure our communications and data by relying on how difficult a math problem is to compute…
Asymmetric encryption algorithms have been mathematically proven to be broken by quantum computers
Post-Quantum Cryptography
A new kind of cryptographic algorithm that can be implemented using today’s classical computers but is also impervious to attacks from future quantum computers
One method is to increase the key size to increase the number of permutations needed to be brute forced
Researchers are working on a wide range of approaches, including lattice-based cryptography and supersingular isogeny key exchange
Ephemeral Key
A cryptographic key that is generated for each execution of a key establishment process
Ephemeral keys are short-lived and used in the key exchange for WPA3 to create perfect forward secrecy
Homomorphic Encryption
An encryption method that allows calculations to be performed on data without decrypting it first
Homomorphic encryption can be used for privacy-preserving outsourced storage and computation
Symmetric Algorithms
DES, 3DES, IDEA, AES, Blowfish, Twofish, RC4, RC5, RC6
Obfuscation
The process of making something unclear
Not impossible to understand
