Symetric Cryptography overview and comparations

Question 1

What are the main advantages of stream ciphers?

Answer 1

• They operate relatively fast since they work on only one character at a time
• Lower error propagation

Question 2

What are the main advantages of block ciphers?

Answer 2

• Higher diffusion since the material of each block affects the entire block
• Single characters cannot be swapped in and out by an attacker.
• Block ciphers have lower malleability (they do not permit attackers to manipulate cipher text with predictable effects on plain text.

Question 3

What are the problems of symmetric cryptography?

Answer 3

• Compromised key means interceptors can decrypt any ciphertext they have acquired (in any point of time)
• Distribution of keys (must be securely transmitted)
• Huge key numbers when more participants (O(n²) , for n participants)

Question 4

Which countermeasure can be done to limit damage of a key in symmetric cryptography?

Answer 4

Change keys frequently.