What if i change nBits to 0x2100ffff, will other nodes accept it? #18235

issue summer-wu opened this issue on March 1, 2020

summer-wu commented at 4:17 PM on March 1, 2020: none

If I change nBits to a hard code number 0x2100ffff ( change GetNextWorkRequired method, always return 0x2100ffff). The hashTarget will be ffff000000000000000000000000000000000000000000000000000000000000.

This hashTarget means nealy every sha256 are valid! A slow PC can generate a block within a second, when I broadcast these blocks to other nodes, will they accept it ( treat it as a valid block)?
summer-wu added the label Bug on Mar 1, 2020
summer-wu renamed this:
~~What if i change nBits to 0x2100ffff, will other node accept it?~~
What if i change nBits to 0x2100ffff, will other nodes accept it?
on Mar 1, 2020
MarcoFalke commented at 8:32 PM on March 1, 2020: member

No, they shouldn't.

Usually the issue tracker is used to track technical issues related to the Bitcoin Core code base. Keep in mind that general bitcoin questions and/or support requests are best directed to the Bitcoin StackExchange or the #bitcoin IRC channel on freenode.
MarcoFalke closed this on Mar 1, 2020
summer-wu commented at 8:05 AM on March 2, 2020: none
I've found the code that reject these kind of attack.

The source that I investigating is 9d2174b (tag: v0.3.1rc1)

in main.cpp , in CBlock::AcceptBlock() wrote:
```
    // Check proof of work
    if (nBits != GetNextWorkRequired(pindexPrev))
        return error("AcceptBlock() : incorrect proof of work");
```
MarcoFalke locked this on Feb 15, 2022

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