Lecture 2 - Secret Key Encryption Flashcards
What does hashing provide?
Integrity
Digital certs or PKIs provide what?
Authentication
Asymmetric encryption provides what?
Key exchange
Symmetric encryption provides what?
Confidentiality
E-voting, or crypto is meant to provide what?
Anonymity
Secret key encryption is also known as symmetric encryption. What does this mean?
Symmetric encryption uses the same key for encryption & decryption
Public key encryption is known as asymmetric encryption. What does this mean?
Asymmetric encryption uses different keys (public & private) for encryption and decryption
List some characteristics of symmetric encryption?
- Uses the same key
- Extremely fast
- Uses smaller keys
- Key exchange is a problem
- Only offers confidentiality
List some characteristics of asymmetric encryption?
- Use different key (public / private)
- Relatively slow
- Bigger keys
- Good at key exchange
- Offers confidentiality and authentication
3-DES, RC4, RC5, AES are examples of what type of encryption
Symmetric encryption
DH, RSA, EIGamal, DSA are examples of what type of encryption
Asymmetric encryption
What is the Diffie-Hellman key exchange?
The Diffie-Hellman key exchange was the first widely used method of safely developing and exchanging keys over an insecure channel.
What is a one-way function in cryptography?
It is easy to compute, but hard to invert.
What is a prime number
A prime number is one that is divisible by itself and 1 only
Be able to write out the Diffie-Helman two step algorithm
A = Gx mod (p)
B = Gy mod (p)
Bob shared key = Bx mod (p)
Alice shared key = Ax mod (p)
Encryption can be categorised as ______ and ______ based
Encryption can be categorised as Stream and Block based
List two examples of Stream Based encryption
RC4 and ChaCha
List some examples of Block Based encryption
RC2, RC5, DES, AES, Blowfish
In terms of key sizes and attacks, what is the main weakness against ciphers?
Brute forcing keys is the main weakness against most ciphers
In terms of “Key Management”, list three methods to share keys
- Offline distribution such as snail mail
- Public key encryption
- Diffie Helman
In terms of symmetric ciphers, what is the block size and key size for AES
- Block size = 128
- Key size = 128,192,256
In terms of symmetric ciphers, what is the block size and key size for DES
- Block size = 64
- Key size = 56
In terms of symmetric ciphers, what is the block size and key size for 3DES
- Block size = 64
- Key size = 112 or 168
