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Secret & unpredictable

Secret sharing & masking shares

A secret can be split so that only a threshold of participants can reconstruct it.

Evaluation card

What “plenty” means here.

Required property
Independent uniform coefficients or masks in the scheme’s finite field.
If it fails
Weak random coefficients can leak information to fewer participants than the threshold promises.
Relevant attacker
A coalition holding some shares, possibly combined with observations of share generation.
The Plenty Line
Generate every random coefficient at the field size and security level required by the sharing scheme.
Why more is not automatically better
Extra source bytes add nothing if mapping into the field is biased or shares are transported insecurely.

Where it appears

Recognize the pattern.

  • 01Shamir secret sharing
  • 02threshold key custody
  • 03secure multiparty computation masks

The Plentropy rule

Protect the requirement, then stop.

Generate every random coefficient at the field size and security level required by the sharing scheme.
Once that claim has comfortable evidence and margin, improve the next limiting factor instead of worshipping a larger entropy number.