< All Cryptography Notes

# tsirhCdneM | Cryptography | Section 2

By: Raul Pop | Related Course: Cryptography | Published: June 15, 2017 | Modified: June 15, 2017
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## CipherText

Privacy/Confidentiality

Plaintext+Initialization Vector=Algorithm+Key=Ciphertext

Initialization Vector(IV) is a process which adds randomness to the beginning of the process so that we get more randomness.And randomness is important with encryption to add complexity(starting point)(psedo randomized starting point)

Algorithm is a collection of math functions

Algorithm symmetric

Algorithm asymmetric

Algorithm symmetric is something like that =the same key is used on both ends . I will use a key to encrypt you will use the same key to decrypt.

Symmetric key use(private key,secret key,shared key,session key)

Symmetric block

Symmetric stream

Asymmetric key

Discrete logarithms

Factorization

The key is the instruction on how we are going to use the algorithm.(Crypto-variable)

## Integrity Checking

1)Accidental modification-HASH(Message Digest)

2)Intentional MAC(Message Authentication Code)-Digital Signature(requires a PKI)

3)Verify origin of message-MAC/Digital Signature

4)Non repudiation-Digital Signature

Mains of cryptography are privacy authentication inteigry non-repudiation(PAIN)

Cryptool session

Cryptool session

## Pro/Cons Symmetric Cryptographic

Con:

Out of band key distribution

Not scalable

No authenticity

Integrity

Non Repudiation

Pro:FAST,FAST,FAST

## Public Key Cryptography

Public key Cryptography

Two keys issued to each user: 1 public key and 1 private key(a key pair)

Anything encrypted with one key can only be decrypted with the other

Provides key exchange scalability and non-repudiation SLOW

## Stream Ciphers ,XOR,RC4

Symmetric Encryption

Stream Ciphers

One bit at a time

XOR transposition,substitution

XOR:

ALIKE=0

DIFFERENT=1

Plain+Key=1+1=0 1+0=1

RC4

Symmetric=Block,Stream

Block:3DES,AES

3DES=Slower more secure

AES=more efficient

Stream RC4(WPE,WPA2)

## Symmetric Encryption

Cryptographic uses of random numbers:

Nonces

Key generation

IV is made out of the pseudo random number.

Symmetric encryption

Ciphers

Confusion/Diffusion

Confusion-Complex math for substitution

Diffusion-Permutations/Rounds

Block ciphers:

ECB

CBC

DES

3DES

AES

Symmetric blockers can be block, straight

Block ciphers going to chuck the data.

Block ciphers are slower but more secure

Triple DES and AES use Block Ciphers.

3DES more processor intensive

AES efficienty standpoint

Key is random,long,short,secret

Algorithm=Open Kerckhoff’s Principle

< All Cryptography Notes
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