xKey: Cryptographic Key Split Custody

The Problem

Cryptographic keys stored in single locations are high-value targets. A single breach exposes the entire cryptographic perimeter.

Hardware Security Modules (HSMs) are expensive, vendor-locked, and still represent a single physical point of failure. Organizations spend millions on HSM infrastructure only to discover that the key material inside is one insider threat, firmware vulnerability, or physical compromise away from total exposure.

Key compromise is catastrophic: a stolen root CA key invalidates every certificate ever issued. A leaked TLS private key enables retroactive decryption of all recorded traffic. A compromised signing key allows forged software updates to propagate to every endpoint. There is no graceful recovery from key theft.

The Old Way

The PRIVATE.ME Solution

XorIDA splits any cryptographic key into N shares distributed across independent custodians. Only K-of-N shares are needed to reconstruct. No single custodian holds usable key material.

Unlike Shamir's Secret Sharing which operates over finite fields with 500-2000x overhead, XorIDA operates over GF(2) to achieve information-theoretic security at near-zero computational cost. A 256-bit key splits in microseconds.

Every share is HMAC-SHA256 verified before reconstruction. Tampered, corrupted, or forged shares are rejected instantly. The system fails closed: if any share fails verification, the entire reconstruction is aborted.

The New Way

How It Works

The key split custody pipeline transforms a single high-value cryptographic key into distributed shares that individually reveal nothing about the original key material.

Use Cases

Integration

import { splitKey, reconstructKey } from '@private.me/keysplit';

// Split a root CA key across 3 custodians (2 needed to reconstruct)
const shares = await splitKey(rootCaKey, custodians, {
  n: 3,
  k: 2,
});

// Distribute shares to independent custodians
await Promise.all(shares.map((s, i) =>
  deliverToCustodian(custodians[i], s)
));

// Reconstruct with any 2 shares
const key = await reconstructKey([shares[0], shares[2]]);

Security Properties

Verifiable Data Protection

Every operation in this ACI produces a verifiable audit trail via xProve. HMAC-chained integrity proofs let auditors confirm that data was split, stored, and reconstructed correctly — without accessing the data itself.

Ready to deploy xKey?

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Ship Proofs, Not Source

xKey generates cryptographic proofs of correct execution without exposing proprietary algorithms. Verify integrity using zero-knowledge proofs — no source code required.

Use Cases