Understanding the One-Time Pad Cipher

The video tutorial explains the concept of encryption using randomness, specifically focusing on the one-time pad method. It begins by discussing the historical problem of designing a cipher that conceals information without patterns. The solution involves using a list of random shifts, which Alice shares with Bob to encrypt messages. This method ensures no repetitive patterns and a uniform frequency distribution, making it impossible for Eve, the code breaker, to decipher the message. The tutorial highlights the strength of the one-time pad through a combinatorial explosion of possibilities, contrasting it with simpler methods like the Caesar Cipher. The visualization of encryption possibilities demonstrates the perfect secrecy achieved by the one-time pad.

What was the main challenge Alice faced in designing a cipher?

• Finding a cipher that is quick to encrypt

• Designing a cipher that hides her fingerprint

• Developing a cipher that is visually appealing

• Creating a cipher that is easy to use

What does Alice use to encrypt her message instead of a code word?

• A list of random shifts

• A secret passphrase

• A complex algorithm

• A public key

What is one of the powerful properties of the encrypted message using random shifts?

• It is shorter than the original message

• It is easy to decode

• It has a repetitive pattern

• It has a uniform frequency distribution

What is the main advantage of using a list of random shifts for encryption?

• It is faster to encrypt

• It prevents frequency analysis

• It requires less computational power

• It is easier to remember

When did the one-time pad emerge as a method of encryption?

• In the early 18th century

• Towards the end of the 19th century

• At the start of the 21st century

• In the mid-20th century

Why is the one-time pad considered the strongest method of encryption?

• It is easy to implement

• It requires no key exchange

• It has a uniform frequency distribution

• It uses a simple algorithm

How does the Caesar Cipher differ from the one-time pad?

• It is based on a random number generator

• It requires a longer key

• It is more secure than the one-time pad

• It uses a single shift for all letters

What is the number of possible encryptions for a five-letter word using the one-time pad?

• 12,000

• 260

• 26

• Almost 12 million

How high would the stack of paper be if every possible encryption of a five-letter word was stacked?

• 10 kilometers

• Over one kilometer

• 500 meters

• 100 meters

What does perfect secrecy mean in the context of the one-time pad?

• The encryption is easy to break

• Every encrypted word is equally likely to be any word

• The encryption is visible to everyone

• The encryption is only temporary