Presentation slides

# Unit 11: Cryptography, Public Key Encryption and Digital Signature

## All Questions

- The total processing speed of microprocessors (based on clock rate and number of circuits) is doubling roughly every year. Today a symmetric session key needs to be 100 bits long to be considered strong. How long will a symmetric session key have to be in 30 years to be considered strong? (Hint: Consider how much longer decryption takes if the key length is increased by a single bit.) Explain.
- Longer keys are more difficult to crack. Most symmetric keys today are 100 to 300 bits long. Why don’t systems use far longer symmetric keys—say, 1,000 bit keys?
- How are digital certificates and drivers’ licenses similar, and how are they different?

## Question 1

The total processing speed of microprocessors (based on clock rate and number of circuits) is doubling roughly every year. Today a symmetric session key needs to be 100 bits long to be considered strong. How long will a symmetric session key have to be in 30 years to be considered strong? (Hint: Consider how much longer decryption takes if the key length is increased by a single bit.) Explain.

## Question 2

Longer keys are more difficult to crack. Most symmetric keys today are 100 to 300 bits long. Why don’t systems use far longer symmetric keys—say, 1,000 bit keys?

## Question 3

How are digital certificates and drivers’ licenses similar, and how are they different?