CRYPTO
BOB P=5 G=2
4
3
2
7
Which generates a shared key
Symetric
Diffie Hellman
Asymetric
Hash
Affine Cipher N=24
192
168
172
146
RSA P=3 Q=5 D=13
4
2
6
3
Public vs Symetric
Public keys more efficient
Public key uses more keys
Symetric keys shorter encryption
Public Based on mathematicl problem
What does Cryptography not deal with
Authentication
Complexity
Integrity
Secrecy
Which crytpoanalysis attack is passive
Replay
Creating new messages
Blocking messages
Modifying messages
Listening
Properties of a crypto hash
Hash cannot be computed without key
Deterministic mapping
Collision resistant
Key revocation
Difficulty of finding an input
One to one mapping
Best definition of cryptography
Combination of both encryption and decryption
a set of methods for decrypting ciphertexts
the science and art of transforming messages
a method of transforming plaintext to ciphertext
CEASER CIPHER VWDBKRPH
COVID19
LOCKDOWN
SAVEME
STAYHOME
Which are correct
XORing a random sequence
All of the group generators are prime
Equivlance of ap-1 = mod p
AES-125 is a secure hash function using 128 bits
M XOR K Cannot be used as encryption
336 =mod 3
Cryptographic hash functions can be used for integrity checking
For a hash function H, there exists differnent messages
Diffie Hellman Protocol
Can be used by 1 person only
Key exchange between 2 parties
Allows both to use a public key to encrypt and decrypt via symmetric cryptography
Allows both to use a public key to encrypt and decrypt via asymmetric cryptography
Man in the middle attack
Attacker intercepts 2 parties
Attack destroys line of communication
Attacker relays messages
Attacker hacks one party
Block Cipher
Encrypts in bits
Encrypts in blocks
Stream cipher
Encrypts byte by byte
Encrypts in blocks
Kerchoff principle
Security of a system should rely on confidentiality of both parties
Security of a system should rely on confidentiality of the underlying algorithm
Security of a system should rely on anonimity of attackers
Security of a system should rely on confidentiality of the key
Security of a system should rely on confidentiality of decryption mechanism
Symetric key
2 Key to encrypt and decrypt
1 Key to encrypt and decrypt
Asymetric key
2 Key to encrypt and decrypt
1 Key to encrypt and decrypt
Monoalphabetic cipher
Each letter of plaintext replaced by another letter based on key
Based on subsititution with multiple substitution alphabets
Polyalphabetic cipher
Based on subsititution with multiple substitution alphabets
Each letter of plaintext replaced by another letter based on key
Hashing
1 Way operation
Removes ability to decrypt
2 Way operation
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