IA 2 - CISCO 4 Flashcards
- science of making and breaking secret codes.
- a way to store and transmit data so only the intended recipient can read or process it.
- Modern ——– uses computationally secure algorithms to make sure that cyber criminals cannot easily compromise protected information.
Cryptography
process of scrambling data so that an unauthorized party cannot easily read it.
Encryption
When enabling encryption, readable data is
cleartext
over the centuries, various cipher methods, physical devices, and aids encrypted and decrypted text
- scytale
- caesar cipher
- vigenere cipher
- enigma machine
while the encrypted version is
encrypted
– letters are rearranged
transposition
Each encryption method uses a specific algorithm, called
cipher
there are several methods of creating ciphertext:
- Transposition
- Substitution
- One-time pad
– letters are replaced
Substitution
Two Types of Encryption
- symmetric algorithm
- asymmetric algorithm
plaintext combined with a secret key creates a new character, which then combines with the plaintext to produce ciphertext
One-time pad
- These algorithms use the same pre-shared key, sometimes called a secret key pair, to encrypt and decrypt data.
- Both the sender and receiver know the pre-shared key before any encrypted communication begins.
- algorithms use the same pre-shared key to encrypt and decrypt data, a method also known as private-key encryption.
Symmetric algorithms
use one key to encrypt data and a different key to decrypt data. One key is public and the other is private.
Asymmetric algorithms
The most common types of cryptography are
- block cipher
- stream cipher
- transform a fixed-length block of plaintext into a common block of ciphertext of 64 or 128 bits.
- usually result in output data that is larger than the input data, because the ciphertext must be a multiple of the block size.
block cipher
- encrypt plaintext one byte or one bit at a time
- the transformation of these smaller plaintext units varies, depending on when they are encountered during the encryption process.
- faster than block ciphers, and generally do not increase the message size, because they can encrypt an arbitrary number of bits.
stream cipher
Some of the common encryption standards that use symmetric encryption include the following
- 3DES
- IDEA
- AES
- encrypts data three times and uses a different key for at least one of the three passes, giving it a cumulative key size of 112-168 bits
3DES - Digital Encryption Standard
The 3DES encryption cycle is as follows:
- Data encrypted by first DES
- Data decrypted by second DES
- Data re-encrypted by third DES
performs eight rounds of transformations on each of the 16 blocks that results from dividing each 64-bit block.
IDEA - International Data Encryption Algorithm
- fixed block size of 128-bits with a key size of 128, 192, or 256 bits.
- strong algorithm that uses longer key lengths.
AES - Advanced Encryption Standard
also called public-key encryption, uses one key for encryption that is different from the key used for decryption
Asymmetrical Encryption
The asymmetric algorithms include:
- RSA
- Diffie-Hellman
- ElGamal
- Elliptic Curve Cryptography (ECC)
- uses the product of two very large prime numbers with an equal length of between 100 and 200 digits.
- Browsers use this to establish a secure connection.
RSA (Rivest-Shamir-Adleman)
- provides an electronic exchange method to share the secret key. Secure protocols, such as Secure Sockets Layer (SSL), Transport Layer Security (TLS), Secure Shell (SSH), and Internet Protocol Security (IPsec), use this.
Diffie-Hellman
- uses the U.S. government standard for digital signatures.
- This algorithm is free for use because no one holds the patent.
ElGamal
includes the generation, exchange, storage, use, and replacement of keys used in an encryption algorithm.
Key management
uses elliptic curves as part of the algorithm. In the U.S., the National Security Agency uses ECC for digital signature generation and key exchange.
Elliptic Curve Cryptography (ECC)
Two terms used to describe keys are:
- key length
- keyspace
his is the number of possibilities that a specific key length can generate.
keyspace
Also called the key size, this is the measure in bits.
key length