xSign: Threshold Authorization

The Problem

Single-signature authorization is a single point of compromise. One stolen credential grants full access. Multi-approval workflows today are procedural, not cryptographic.

Enterprise authorization systems rely on role-based access control enforced by a central identity provider. If that provider is compromised, every role it governs is compromised. Multi-approval workflows exist as UI checkboxes, not cryptographic enforcement.

Hardware tokens and MFA add friction but still funnel through a single decision point. An attacker who compromises the authorization service can approve any operation, regardless of how many humans were supposed to review it.

The Old Way

The PRIVATE.ME Solution

xSign splits authorization payloads into shares for K-of-N approvers. Each share is HMAC-signed and bound to a specific operation via SHA-256. Authorization requires cryptographic quorum.

No single approver holds enough information to authorize an operation alone. Each share is cryptographically bound to the specific operation being approved — shares cannot be repurposed for different operations.

The threshold is configurable: 2-of-3 for routine operations, 3-of-5 for critical changes, 4-of-7 for irreversible actions. Escalation is structural, not procedural.

The New Way

How It Works

An authorization request flows through operation binding, XorIDA splitting across N approvers, share collection, HMAC verification, and threshold reconstruction to produce a cryptographic authorization token.

Use Cases

Integration

import { requestAuth, approveShare } from '@private.me/authorize';

// Create a 2-of-3 authorization request
const authReq = await requestAuth(
  { operation: 'wire_transfer', amount: 500000, currency: 'USD' },
  ['cfo@corp.com', 'coo@corp.com', 'treasurer@corp.com'],
  { n: 3, k: 2 }
);

// Each approver signs their share independently
const approval = await approveShare(authReq.shareId, approverKey);

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 xSign?

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Ship Proofs, Not Source

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

Use Cases