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BIP93: correct threshold range #2023

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BIP93: correct threshold range #2023

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Update bip-0093.mediawiki
Lil-Duckling-22 Oct 29, 2025
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2 changes: 1 addition & 1 deletion bip-0093.mediawiki
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Expand Up @@ -20,7 +20,7 @@ This document describes a standard for backing up and restoring the master seed
[https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki BIP-0032] hierarchical deterministic wallet, using Shamir's secret sharing.
It includes an encoding format, a BCH error-correcting checksum, and algorithms for share generation and secret recovery.
Secret data can be split into up to 31 shares.
A minimum threshold of shares, which can be between 1 and 9, is needed to recover the secret, whereas without sufficient shares, no information about the secret is recoverable.
A minimum threshold of shares, which can be 0 (for unshared secret) or between 2 and 9 (for shares), is needed to recover the secret, whereas without sufficient shares, no information about the secret is recoverable.
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@jonatack jonatack Nov 4, 2025 •
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Not sure about this change.

The current abstract states "between 1 and 9" for what "is needed to recover the secret".

And the Recovering Master Seed section stipulates: "The first character of the data part indicates the threshold of the share, and it is required to be a non-"0" digit."

So these two excerpts seem to concur? Perhaps it could be clearer.

cc @apoelstra for feedback

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@BenWestgate BenWestgate Nov 6, 2025 •
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It's correct as it is.

Threshold is a value 1 through 9 and refers to the number of strings needed to recover the seed.

k is the literal first numeric character of the bech32 data so it cannot be "1" even if the threshold is 1. "0" is recommended for unshared secrets (threshold 1) although any numeric value is allowed as it is ignored when share_idx = "s".

Whether it is clear or not is another matter. You'd have to read the body to know these details so I think the abstract is fine. There may be some conflation of "threshold" with "threshold digit" which is called k in the codex book and many reference implementations, which is what lead you to opening this PR.


===Copyright===

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