Proof of work-proof of workload

Brief description:

The "proof of work" tool may be used in spam and dossystems. In short, it is a proof that you have been working for a certain amount of time.

Of course, this is only for one side. The other side of the game should have a very simple way to verify whether your answer is correct.

For example:

B has a problem for a, or a finds a problem by himself. A takes 10 minutes to prove a problem and then sends the answer to B, B verifies that the answer is correct in less than one second.

In this way, it can be used in computer systems in such a situation:

A requests a service of B. If a can request a large number of requests within a period of time, it may cause B to crash. Therefore, B issues a question to the service requestor, or you can agree on a "answer-Verification" protocol.

It takes some time to calculate this question. After calculation, a B verification will be sent, and B will be able to complete the verification in an instant, pass the verification, and then provide services to.

If a is an attacker, the time spent × the target object N is a considerable CPU computing investment, so it can effectively prevent malicious attacks.

"Workload proof" tool:

Here is a list of known proof-of-work functions:

• Integer square root modulo a large prime^[8]
• Weaken fiat-Shamir signatures^[8]
• Ong-Schnorr-Shamir signature broken by Pollard^[8]
• Partial hash Inversion^{[9][10][11][12] As hashcash}
• Hash Sequences^[13]
• Puzzles^[14]
• Diffie-Hellman-based puzzle^[15]
• Moderate^[4]
• Mbound^[5]
• Hokkaido^[6]
• Merkle tree based^[16]
• Guided Tour puzzle Protocol^[7]

Hashcash

For example, the hashcash tool proposed by Adam back inspired the bitcoin system.

Hashcash can be used to prevent spam.

The sender needs to append a random to the head of the mail header, and then sha1-160 the string. If the first 20 bits of hash are 0, then solved is sent to the receiver.

After receiving the message, the recipient also hash the string found by sender. The first 20 bits are indeed 0, so they thought that sender did a hard job in hash search, so I believe that sender is not a spam maker, and sender may be sent by a normal email object.

In this case, the workload is probably, after the 20-power random search of 2, we can find a hash with the first 20 bits being 0, that is, the answer. Because of the first 20 bits, the probability of each bit being 0 is 1/2, and the total probability is 1/(20 power of 2 ).

The receiver's verification is extremely simple.