Function FBTC

Our research assessment is adverse. FBTC, Function Network’s Bitcoin-backed omnichain asset, is unrelated to Fidelity’s spot Bitcoin ETF that trades under the same ticker. It follows the same custodial structure as WBTC and BTCB, both already rejected in this registry: BTC held by named custodians, minted 1:1 by KYB-gated Merchants, with retail exit only through secondary markets. A three-member Security Council of Mantle, Antalpha Prime, and Cobo oversees custody through threshold-signature and MPC techniques. This separates roles more clearly than WBTC does, but this review could not confirm the exact approval threshold among the three parties, and found no independent, third-party proof-of-reserves attestation. The absence of a named scandal does not offset an unconfirmed custody threshold and no independent reserve verification. This is a standing disclosure gap, not a temporary evidence gap.

Review triggers: events that reopen the verdict
• An independent, third-party proof-of-reserves attestation for FBTC is published on a recurring basis
• The exact Security Council or TSS approval threshold is publicly confirmed and shown to require genuine multi-party consensus with no single-party override path
• A permissionless or clearly disclosed, non-discriminatory redemption path is demonstrated for non-institutional holders
• Twelve consecutive months with no custody, freeze, or minting-irregularity incident following threshold confirmation

Watched nightly: a warning on its venues or files, or a cited document that changes, reopens the memo. The first confirmation is due 2026-11-17.

The research file

Mechanism

A user deposits BTC to a Merchant-specific custodial deposit address. The deposit is verified and triggers 1:1 FBTC minting on the destination chain, which includes Ethereum, Mantle, and BNB Chain. Deposit and withdrawal addresses use MPC and multi-signature techniques, so no single party holds unilateral custody access. Redemption reverses the flow: FBTC is burned, the burn is verified, and BTC is released from custody.

Control and governance

A three-member Security Council of Mantle, Antalpha Prime, and Cobo oversees custody via a threshold-signature scheme and MPC, audits code, and approves upgrades. Function’s own documentation says no single member can act alone. Named contract roles include Custodians, financial institutions holding BTC in MPC addresses; Merchants, KYB-gated parties who mint and burn; a Pauser that can halt contract functions when it detects risk; a Safety Committee Member that can execute emergency burns during a crisis; and a Contract Owner that executes upgrades through a Safe multisig gated by Security Council approval. This review did not confirm the exact signing threshold for Security Council or TSS approval, such as 2-of-3 versus 3-of-3. That threshold has a material effect on how concentrated actual control is despite the stated split in roles.

Incident record

This review identified no depeg, exploit, or custody-failure incident for FBTC through its 2026-08-17 search cutoff. That is a limited negative finding, not proof of a clean record. Public disclosure for FBTC is thinner than for WBTC, and audits from BlockSec, Secure3, and MixBytes are listed without specific dates or scope confirmed in this pass.

Exit

Only KYB-verified qualified users can mint or redeem at par, the same structure as WBTC’s Merchant-gated model. Retail holders acquire and exit FBTC through secondary-market swaps rather than direct redemption. This review found no independent, third-party proof-of-reserves attestation. The backing claims rely on the Security Council’s own custody oversight rather than an external verifier.

Comparison

WBTC is also rejected in this registry after BiT Global’s 2-of-3 custody-key concentration transition was completed. FBTC’s three named institutional custodians have no comparable controversial-individual red flag, and its split in roles is more clearly documented on paper. But FBTC is newer, has thinner independent reserve verification, and has an unconfirmed approval threshold. It is not clearly more decentralized than WBTC’s current structure, only concentrated differently in a way this review cannot yet approve.

Sources

The claims above trace to these. Where a number could not be independently verified, the thesis says so.

• FBTC whitepaper v1.1 · primary · accessed 2026-08-17
  Supports: mechanism
• FBTC Docs — roles · primary · accessed 2026-08-17
  Supports: role and authority map
• FBTC Docs — custodial addresses · primary · accessed 2026-08-17
  Supports: custody architecture
• FBTC Docs — pausing · primary · accessed 2026-08-17
  Supports: pause mechanism
• FBTC Docs — audit reports · primary · accessed 2026-08-17
  Supports: BlockSec, Secure3, MixBytes audits listed
• Bitcoin Foundation — what is FBTC crypto, Bitcoin vs Function FBTC · secondary · accessed 2026-08-17
  Supports: disambiguation from Fidelity ETF, Security Council composition

Inherited controls

The research above describes the protocol layer. Every position also inherits the asset it holds and the chain it settles on. The layer with the most administrative power sets the position’s effective control; that describes control, not quality or suitability.