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bip-325: document signet minimum difficulty #2056

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jonatack merged 1 commit into from
Dec 15, 2025
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bip-325: document signet minimum difficulty #2056

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9 changes: 9 additions & 0 deletions bip-0325.mediawiki
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Expand Up @@ -75,6 +75,15 @@ A block is considered fully validated only if the to_sign transaction is a valid

There is one other acceptable special case: if a block's challenge is e.g. `OP_TRUE` (`0x51`), where an empty solution would result in success, the block is also considered valid if the signet commitment is absent.

=== Minimum Difficulty ===

The minimum difficulty for blocks in signet is approximately
0.0011265, corresponding to a maximum target of
<code>00000377ae000000000000000000000000000000000000000000000000000000</code>
which is represented by an nBits value of <code>0x1e0377ae</code>.
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@jonatack jonatack Dec 15, 2025 •
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Verified the maximum target and nBits values correspond to those for signet in src/kernel/chainparams.cpp in Bitcoin Core:

consensus.powLimit = uint256{"00000377ae000000000000000000000000000000000000000000000000000000"};

.../...

genesis = CreateGenesisBlock(1598918400, 52613770, 0x1e0377ae, 1, 50 * COIN);

Edit: verified that these values yield a minimum difficulty of ~0.0011265.


This value is chosen so that multiplying the maximum target by maximum retarget timespan (8 weeks measured in seconds) does not overflow a uint256, making it easier to do difficulty adjustment calculations.

== Genesis Block and Message Start ==

The genesis block is the same for all signet networks, whereas the message start is defined as the first four bytes of the sha256d of the challenge script as a single data push (see below).
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