(a) If the difficulty target for a Bitcoin Proof-of-Work is given by the hash value "0000000000000001F24D00000000000000000000000000000000000000000000",

discuss if the following hash value will be accepted as a valid block header hash. Discuss your reason.

00000000000000000067bb06e03aaaa877a02c4f0deb34fdd7d1f441aba830e8

What is the average number of tries needed for a miner to obtain this hash value?

(b) A clinic stores its patients' medical record in a database using the following form:

A visitor to the clinic will supply its name, which will be used by the nurse to perform a lookup in the database for two purposes: 

(1) check for existing patient record, 

(2) retrieve patient record if this is not the first visit. 

 

The nurse will then use the secret key k to decrypt the patient's record for subsequent processing.

Based on your understanding of hash function, discuss one advantage of the recording method. Identify one potential flaw of this implementation and propose an improvement.

 

(c) There are three types of blockchain implementations - public blockchain, private blockchain, and consortium blockchain. Inspect if confidentiality, availability, and user authentication are needed in each type of implementation.

Hash(Patient's Name) Encrypt(k, Name, Age, Date of Visit, Identification Number)