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| author | murilo ijanc | 2026-03-24 21:45:05 -0300 |
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| committer | murilo ijanc | 2026-03-24 21:45:05 -0300 |
| commit | 01c17c68277ff88fab812920732d9bbe9e6bb571 (patch) | |
| tree | 035398ae34263b981b621c6275835d2cc6847d57 /news/phase4-shamir-heir-recovery | |
| parent | f186b71ca51e83837db60de13322394bb5e6d348 (diff) | |
| download | website-01c17c68277ff88fab812920732d9bbe9e6bb571.tar.gz | |
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diff --git a/news/phase4-shamir-heir-recovery/index.html b/news/phase4-shamir-heir-recovery/index.html deleted file mode 100644 index 3acf79a..0000000 --- a/news/phase4-shamir-heir-recovery/index.html +++ /dev/null @@ -1,199 +0,0 @@ -<!DOCTYPE html> -<html lang="en"> -<head> - <meta charset="utf-8"> - <meta name="viewport" content="width=device-width, initial-scale=1"> - <title>Phase 4: Heir Key Recovery with Shamir's Secret Sharing — Tesseras</title> - <meta name="description" content="Tesseras now lets you split your cryptographic identity into shares distributed to trusted heirs — any threshold of them can reconstruct your keys, but fewer reveal nothing."> - <!-- Open Graph --> - <meta property="og:type" content="article"> - <meta property="og:title" content="Phase 4: Heir Key Recovery with Shamir's Secret Sharing"> - <meta property="og:description" content="Tesseras now lets you split your cryptographic identity into shares distributed to trusted heirs — any threshold of them can reconstruct your keys, but fewer reveal nothing."> - <meta property="og:image" content="https://tesseras.net/images/social.jpg"> - <meta property="og:image:width" content="1200"> - <meta property="og:image:height" content="630"> - <meta property="og:site_name" content="Tesseras"> - <!-- Twitter Card --> - <meta name="twitter:card" content="summary_large_image"> - <meta name="twitter:title" content="Phase 4: Heir Key Recovery with Shamir's Secret Sharing"> - <meta name="twitter:description" content="Tesseras now lets you split your cryptographic identity into shares distributed to trusted heirs — any threshold of them can reconstruct your keys, but fewer reveal nothing."> - <meta name="twitter:image" content="https://tesseras.net/images/social.jpg"> - <link rel="stylesheet" href="https://tesseras.net/style.css?h=21f0f32121928ee5c690"> - - - <link rel="alternate" type="application/atom+xml" title="Tesseras" href="https://tesseras.net/atom.xml"> - - - <link rel="icon" type="image/png" sizes="32x32" href="https://tesseras.net/images/favicon.png?h=be4e123a23393b1a027d"> - -</head> -<body> - <header> - <h1> - <a href="https://tesseras.net/"> - <img src="https://tesseras.net/images/logo-64.png?h=c1b8d0c4c5f93b49d40b" alt="Tesseras" width="40" height="40" class="logo"> - Tesseras - </a> - </h1> - <nav> - - <a href="https://tesseras.net/about/">About</a> - <a href="https://tesseras.net/news/">News</a> - <a href="https://tesseras.net/releases/">Releases</a> - <a href="https://tesseras.net/faq/">FAQ</a> - <a href="https://tesseras.net/subscriptions/">Subscriptions</a> - <a href="https://tesseras.net/contact/">Contact</a> - - </nav> - <nav class="lang-switch"> - - <strong>English</strong> | <a href="/pt-br/news/phase4-shamir-heir-recovery/">Português</a> - - </nav> - </header> - - <main> - -<article> - <h2>Phase 4: Heir Key Recovery with Shamir's Secret Sharing</h2> - <p class="news-date">2026-02-15</p> - <p>What happens to your memories when you die? Until now, Tesseras could preserve -content across millennia — but the private and sealed keys died with their -owner. Phase 4 continues with a solution: Shamir's Secret Sharing, a -cryptographic scheme that lets you split your identity into shares and -distribute them to the people you trust most.</p> -<p>The math is elegant: you choose a threshold T and a total N. Any T shares -reconstruct the full secret; T-1 shares reveal absolutely nothing. This is not -"almost nothing" — it is information-theoretically secure. An attacker with one -fewer share than the threshold has exactly zero bits of information about the -secret, no matter how much computing power they have.</p> -<h2 id="what-was-built">What was built</h2> -<p><strong>GF(256) finite field arithmetic</strong> (<code>tesseras-crypto/src/shamir/gf256.rs</code>) — -Shamir's Secret Sharing requires arithmetic in a finite field. We implement -GF(256) using the same irreducible polynomial as AES (x^8 + x^4 + x^3 + x + 1), -with compile-time lookup tables for logarithm and exponentiation. All operations -are constant-time via table lookups — no branches on secret data. The module -includes Horner's method for polynomial evaluation and Lagrange interpolation at -x=0 for secret recovery. 233 lines, exhaustively tested: all 256 elements for -identity/inverse properties, commutativity, and associativity.</p> -<p><strong>ShamirSplitter</strong> (<code>tesseras-crypto/src/shamir/mod.rs</code>) — The core -split/reconstruct API. <code>split()</code> takes a secret byte slice, a configuration -(threshold T, total N), and the owner's Ed25519 public key. For each byte of the -secret, it constructs a random polynomial of degree T-1 over GF(256) with the -secret byte as the constant term, then evaluates it at N distinct points. -<code>reconstruct()</code> takes T or more shares and recovers the secret via Lagrange -interpolation. Both operations include extensive validation: threshold bounds, -session consistency, owner fingerprint matching, and BLAKE3 checksum -verification.</p> -<p><strong>HeirShare format</strong> — Each share is a self-contained, serializable artifact -with:</p> -<ul> -<li>Format version (v1) for forward compatibility</li> -<li>Share index (1..N) and threshold/total metadata</li> -<li>Session ID (random 8 bytes) — prevents mixing shares from different split -sessions</li> -<li>Owner fingerprint (first 8 bytes of BLAKE3 hash of the Ed25519 public key)</li> -<li>Share data (the Shamir y-values, same length as the secret)</li> -<li>BLAKE3 checksum over all preceding fields</li> -</ul> -<p>Shares are serialized in two formats: <strong>MessagePack</strong> (compact binary, for -programmatic use) and <strong>base64 text</strong> (human-readable, for printing and physical -storage). The text format includes a header with metadata and delimiters:</p> -<pre><code>--- TESSERAS HEIR SHARE --- -Format: v1 -Owner: a1b2c3d4e5f6a7b8 (fingerprint) -Share: 1 of 3 (threshold: 2) -Session: 9f8e7d6c5b4a3210 -Created: 2026-02-15 - -<base64-encoded MessagePack data> ---- END HEIR SHARE --- -</code></pre> -<p>This format is designed to be printed on paper, stored in a safe deposit box, or -engraved on metal. The header is informational — only the base64 payload is -parsed during reconstruction.</p> -<p><strong>CLI integration</strong> (<code>tesseras-cli/src/commands/heir.rs</code>) — Three new -subcommands:</p> -<ul> -<li><code>tes heir create</code> — splits your Ed25519 identity into heir shares. Prompts for -confirmation (your full identity is at stake), generates both <code>.bin</code> and -<code>.txt</code> files for each share, and writes <code>heir_meta.json</code> to your identity -directory.</li> -<li><code>tes heir reconstruct</code> — loads share files (auto-detects binary vs text -format), validates consistency, reconstructs the secret, derives the Ed25519 -keypair, and optionally installs it to <code>~/.tesseras/identity/</code> (with automatic -backup of the existing identity).</li> -<li><code>tes heir info</code> — displays share metadata and verifies the checksum without -exposing any secret material.</li> -</ul> -<p><strong>Secret blob format</strong> — Identity keys are serialized into a versioned blob -before splitting: a version byte (0x01), a flags byte (0x00 for Ed25519-only), -followed by the 32-byte Ed25519 secret key. This leaves room for future -expansion when X25519 and ML-KEM-768 private keys are integrated into the heir -share system.</p> -<p><strong>Testing</strong> — 20 unit tests for ShamirSplitter (roundtrip, all share -combinations, insufficient shares, wrong owner, wrong session, threshold-1 -boundary, large secrets up to ML-KEM-768 key size). 7 unit tests for GF(256) -arithmetic (exhaustive field properties). 3 property-based tests with proptest -(arbitrary secrets up to 5000 bytes, arbitrary T-of-N configurations, -information-theoretic security verification). Serialization roundtrip tests for -both MessagePack and base64 text formats. 2 integration tests covering the -complete heir lifecycle: generate identity, split into shares, serialize, -deserialize, reconstruct, verify keypair, and sign/verify with reconstructed -keys.</p> -<h2 id="architecture-decisions">Architecture decisions</h2> -<ul> -<li><strong>GF(256) over GF(prime)</strong>: we use GF(256) rather than a prime field because -it maps naturally to bytes — each element is a single byte, each share is the -same length as the secret. No big-integer arithmetic, no modular reduction, no -padding. This is the same approach used by most real-world Shamir -implementations including SSSS and Hashicorp Vault.</li> -<li><strong>Compile-time lookup tables</strong>: the LOG and EXP tables for GF(256) are -computed at compile time using <code>const fn</code>. This means zero runtime -initialization cost and constant-time operations via table lookups rather than -loops.</li> -<li><strong>Session ID prevents cross-session mixing</strong>: each call to <code>split()</code> generates -a fresh random session ID. If an heir accidentally uses shares from two -different split sessions (e.g., before and after a key rotation), -reconstruction fails cleanly with a validation error rather than producing -garbage output.</li> -<li><strong>BLAKE3 checksums detect corruption</strong>: each share includes a BLAKE3 checksum -over its contents. This catches bit rot, transmission errors, and accidental -truncation before any reconstruction attempt. A share printed on paper and -scanned back via OCR will fail the checksum if a single character is wrong.</li> -<li><strong>Owner fingerprint for identification</strong>: shares include the first 8 bytes of -BLAKE3(Ed25519 public key) as a fingerprint. This lets heirs verify which -identity a share belongs to without revealing the full public key. During -reconstruction, the fingerprint is cross-checked against the recovered key.</li> -<li><strong>Dual format for resilience</strong>: both binary (MessagePack) and text (base64) -formats are generated because physical media has different failure modes than -digital storage. A USB drive might fail; paper survives. A QR code might be -unreadable; base64 text can be manually typed.</li> -<li><strong>Blob versioning</strong>: the secret is wrapped in a versioned blob (version + -flags + key material) so future versions can include additional keys (X25519, -ML-KEM-768) without breaking backward compatibility with existing shares.</li> -</ul> -<h2 id="what-comes-next">What comes next</h2> -<ul> -<li><strong>Phase 4 continued: Resilience and Scale</strong> — advanced NAT traversal -(STUN/TURN), performance tuning (connection pooling, fragment caching, SQLite -WAL), security audits, institutional node onboarding, OS packaging</li> -<li><strong>Phase 5: Exploration and Culture</strong> — public tessera browser by -era/location/theme/language, institutional curation, genealogy integration, -physical media export (M-DISC, microfilm, acid-free paper with QR)</li> -</ul> -<p>With Shamir's Secret Sharing, Tesseras closes the last critical gap in long-term -preservation. Your memories survive infrastructure failures through erasure -coding. Your privacy survives quantum computers through hybrid encryption. And -now, your identity survives you — passed on to the people you chose, requiring -their cooperation to unlock what you left behind.</p> - -</article> - - </main> - - <footer> - <p>© 2026 Tesseras Project. <a href="/atom.xml">News Feed</a> · <a href="https://git.sr.ht/~ijanc/tesseras">Source</a></p> - </footer> -</body> -</html> diff --git a/news/phase4-shamir-heir-recovery/index.html.gz b/news/phase4-shamir-heir-recovery/index.html.gz Binary files differdeleted file mode 100644 index f4b1598..0000000 --- a/news/phase4-shamir-heir-recovery/index.html.gz +++ /dev/null |