Service Notice

VDF Algorithm Label Correction

Notice ID: vdf-correction-202609 Issued: 2026-09-09 Status: Resolved

Before 2026-09-01 04:02 UTC, responses from /v1/rng/latest included the field "vdf": "wesolowski-2048" — claiming Wesolowski RSA-2048 Verifiable Delay Function. The underlying engine during that period was an iterated SHA-256 chain. This was a metadata labeling error. The correction was deployed on 2026-09-01.

Affected Endpoint & Period

Field	Value
Endpoint	`GET /v1/rng/latest` (x402.fairseal.io)
Affected period	Purchases prior to 2026-09-01 04:02 UTC
Incorrect label	`"vdf": "wesolowski-2048"`
Actual engine	Iterated SHA-256 chain (sequential, non-parallelizable)
Corrected label	`"vdf": "wesolowski-2048"` (genuine Wesolowski RSA-2048 since 2026-09-01)

What This Means

Both iterated SHA-256 chain and Wesolowski RSA-2048 VDF are sequential, non-parallelizable computations. However, they are not equivalent. The distinction matters if your application relied on Wesolowski-specific properties:

Fast independent verification — Wesolowski proofs allow sub-second verification of the delay claim; SHA-256 chain verification scales linearly with chain length.
RSA-2048 group-squaring hardness — the security assumption differs between the two constructions.
Formal Wesolowski proof objects — receipts during the affected period do not contain a genuine Wesolowski proof.

If your application specifically depended on any of the above Wesolowski properties during the affected period, the receipts from that window cannot be used to substantiate those claims.

The randomness values themselves remain sequentially computed and non-parallelizable — the fairness property (output not predictable before computation) was maintained throughout.

Timeline

Before 2026-09-01 04:02 UTC

All /v1/rng/latest responses labeled VDF as "wesolowski-2048". Underlying engine was iterated SHA-256 chain.

2026-09-01

Genuine Wesolowski RSA-2048 VDF engine deployed. All new receipts carry correct algorithm label and actual Wesolowski proof objects. Epoch 831765 independently verified on deployment.

2026-09-02

24-hour burn-in complete: 113/113 wesolowski_proof objects validated, CPU load nominal, epoch progression confirmed.

2026-09-09

This notice published. Service_notices added to .well-known/x402 on both api.fairseal.io and x402.fairseal.io. Landing page, llms.txt, and verify page updated.

Verification of Current Engine

To confirm the current engine is genuine Wesolowski RSA-2048:

Call GET https://x402.fairseal.io/v1/rng/latest (x402, USDC on Base)
Receipt will contain "vdf": "wesolowski-2048" and a "wesolowski_proof" object with T, pi, and l fields
Verify using @fairseal/verify: import { verifyVEO } from '@fairseal/verify'

✅ This issue is resolved. All responses from /v1/rng/latest after 2026-09-01 04:02 UTC use genuine Wesolowski RSA-2048 VDF with verifiable proof objects. Receipts issued since that time carry the correct algorithm label and can be independently verified using the SDK.

Affected Buyers

If your application made decisions based on Wesolowski-specific properties using receipts from before 2026-09-01 04:02 UTC, please contact us at hello@fairseal.io. We are available to discuss the impact on your specific use case.