How does consensus make it difficult to rewrite existing blocks in Multichain?

Question

(Careful not to use the word Immutable as Immutability is not absolute)

In Bitcoin, Proof of Work is used to make it computationally difficult to edit an existing block due to the fact that the subsequent blocks also have to be REmined, requiring a lot of compute power. Am I correct in assuming that in Multichain, once a block is edited, the subsequent blocks need to be REmined in a round-robin fashion?

If so, why does a block in Multichain still contain a difficulty level and a nonce? I thought these properties were associated to Proof of Work.

Thanks,

Charlie

Answer 1

Yes, you are correct in your categorization of round-robin "immutability".

MultiChain blocks contain a difficulty level and a nonce because MultiChain is fully compatible with the bitcoin protocol and block format (and can also be configured with proof-of-work mining if you prefer). This makes life much easier for developers who can repurpose the vast ecosystem of bitcoin tools to work with MultiChain.

If you use MultiChain with the default settings, the difficulty stays very low, just requiring the first 8 bits of the block hash to be zeroes. This means that on average, only 256 nonces have to be tried for each block. The performance impact is negligible. (Remember that only the block header has to be hashed.) We keep it at this level so that block hashes are recognizable as different from (most) transaction hashes.