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

Community

Links

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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

Owner

Blockchain Commons LLC (not-for-profit benefit corporation founded by Christopher Allen, April 25, 2019; Berkeley, California). Specification authors: Wolf McNally, Christopher Allen

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

Last Investigated Jul 1, 2026

Use Case Domains

Co-Creation & Knowledge

Semantic & Data Protocol Attributes

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

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

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