SSKR

Semantic & Data Protocol

Specification for Sharded Secret Key Reconstruction — a method for splitting a secret (typically a cryptographic seed) into N shares such that any K (the threshold) of them can reconstruct the secret. Implements Shamirs Secret Sharing with two-tier sharding for hierarchical share distribution and is BIP-39 compatible. Shares can be encoded as Bytewords, URs, or Gordian Envelopes (the recommended modern form). Designed to address the Single Point of Failure problem in self-custody without introducing a Single Point of Compromise — shares can be distributed to friends, family, or fiduciaries who can return them in emergency for seed recovery. Functionally a successor to SLIP-39, with broader output options and integration with the Gordian stack

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Details

License BSD-2-Clause Plus Patent License — bc-sskr (C), bc-sskr-rust, bc-shamir
Dev Status 🟢 Active
Dev Status Detail Community review stage / production use in self-custody tools — bc-sskr (C), bc-sskr-rust, bc-shamir reference libraries; integrated with Gordian Seed Tool, LetheKit, seedtool Reclassified 2026-09-14: text states 'production use in self-custody tools' directly — an explicit production claim, not inferred.
Owner Blockchain Commons LLC (not-for-profit benefit corporation founded by Christopher Allen, April 25, 2019; Berkeley, California). Specification authors: Wolf McNally, Christopher Allen
Owner - List
  • Blockchain Commons
Governing Body Blockchain Commons LLC (not-for-profit benefit corporation)
Governing Body - List
  • Blockchain Commons
Country USA (Berkeley, California)
Start Year 2020
Stack Reference libraries: C (bc-sskr, bc-shamir), Rust (bc-sskr-rust); CLI tooling via bc-envelope-cli for Envelope-wrapped shares
Funding Blockchain Commons donations and patron sponsorships
Funding - List
  • Blockchain Commons
Last Investigated Sep 14, 2026

Topology view

This tool in the centre and the things it is directly related to. Each line names the kind of relationship.

Topology view: SSKRThis tool in the centre and the things it is directly related to. Each line names the kind of relationship.SSKRGordian Clubs (Basis for, Composes with, Interoperates with)GordianClubsXID (Basis for, Composes with)XIDdCBOR (Composes with)dCBORGordian Envelope (Composes with, Conforms to, Speaks protocol)GordianEnvelopeHubert (Composes with)HubertUniform Resources (Composes with)UniformResourcesBlockchain Commons (Developed by, Funded by, Stewarded by)BlockchainCommonsBitcoin (Succeeds)BitcoinGordian Suite (Member of suite)GordianSuite
  • Gordian Clubs (Tool): Basis for, Composes with, Interoperates with
  • XID (Tool): Basis for, Composes with
  • dCBOR (Tool): Composes with
  • Gordian Envelope (Tool): Composes with, Conforms to, Speaks protocol
  • Hubert (Tool): Composes with
  • Uniform Resources (Tool): Composes with
  • Blockchain Commons (Organization): Developed by, Funded by, Stewarded by
  • Bitcoin (Tool): Succeeds
  • Gordian Suite (Suite): Member of suite

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Use Case Domains

Co-Creation & Knowledge

Affordances

Data portability Local-first storage

Semantic & Data Protocol Attributes

Owner - List
  • Blockchain Commons
Origins Blockchain Commons; conceptual successor to SLIP-39
Database N/A — cryptographic primitive specification, not a storage system
Query Language N/A — cryptographic primitive
Data Formats Shares encoded via Bytewords, UR (ur:sskr), or Gordian Envelope (recommended for metadata-rich use cases supporting multiple secrets and labels)
Collaborative Live Editing N/A — cryptographic primitive
Rich Text Editing N/A — cryptographic primitive
Mobile Support Yes — Swift library on iOS via BCLibsSwift; Gordian Seed Tool iOS app uses SSKR; library coverage across mobile platforms via Rust and Swift bindings
Web Support Yes — TypeScript library (sskr by Leonardo Custodio); web-compatible CBOR serialization
Native Apps Yes — used in Gordian Seed Tool (iOS/macOS), LetheKit (DIY hardware), seedtool (CLI)
Terms Open standard, BSD-2-Clause Plus Patent License
Funding - List
  • Blockchain Commons
Funds Unknown — funded under Blockchain Commons general operating budget; specific SSKR allocation not separately published
Based On Shamirs Secret Sharing (with hashed-secret modification reducing information-theoretic to computational security in exchange for malicious-share detection); BIP-39 compatibility; CBOR (via UR or Envelope encoding); Bytewords
Governing Body - List
  • Blockchain Commons
Semantic Web Compatibility Shares can carry metadata via Gordian Envelope wrapping (names, notes, creation date); modest semantic capability via Known Values
Protocol Maturity / Standardization BCR-2020-011 (Blockchain Commons Research paper); reference libraries deployed in production self-custody tools; positioned as successor to SLIP-39 in Bitcoin/digital-asset space
Vocabulary / Ontology Type Specification of share encoding format and threshold reconstruction parameters; not a vocabulary
Usage Pattern Self-custody seed backup; multi-party threshold escrow; emergency recovery via trusted holders; integration with FROST and Gordian Clubs as a permit type

Relationships

How this tool connects to other tools and organizations, from relationships reviewed by the OpenHaven data steward. They describe how projects connect, not how good they are.

Conforms to
Developed by
  • Blockchain Commons
Funded by
  • Blockchain Commons
Member of suite
  • Gordian Suite
Speaks protocol
Stewarded by
  • Blockchain Commons
Composes with
Interoperates with
Basis for
Succeeds