Silent Payments: Bandwidth Requirements and Trust Risks for Mobile Bitcoin Wallets

Silent Payments enable reusable Bitcoin addresses without exposing a visible chain of transactions. The recipient’s wallet scans the blockchain for outputs that match a derived Taproot destination, a process that has been challenging for mobile devices.

Bandwidth Findings

A measurement project processed every block from height 709,656 to 965,089 (255,434 blocks) and calculated that the complete BlindBit v2 scanning payload totals 15.08 GB, averaging 59 KB per block. Using recent‑era data (heights 900,000‑965,089) and assuming 144 blocks per day, the daily download requirement is roughly 8 MB.

Alternative Filtering Approach

The same study modeled a lighter route using Taproot‑only filters and raw tweaks, amounting to about 7.14 GB for the entire history. This method adds full‑block downloads for each filter match, so actual traffic varies with wallet activity.

Trust Implications of Indexers

Light wallets cannot derive the necessary data themselves and must rely on an indexer. If the indexer omits a tweak needed for a payment, the wallet will not detect the incoming transaction, leading to silent loss of funds. An issue reported for Cake Wallet in July 2025 highlighted how a wallet could consider a range of blocks complete after receiving incomplete data, preventing a later rescan from retrieving the missing payment.

Mitigations and Future Work

• Use multiple indexers that publish commitments to their tweak sets, allowing cross‑verification.
• Rescan from an earlier block against a trusted source or employ a full‑node‑backed scan.
• Develop wallet safeguards that detect incomplete history before finalizing sync.

Current Adoption

Several wallets have begun integrating Silent Payments support. Sparrow Wallet 2.5.0 (May 2026) added receiving capabilities with a default public Frigate server. Other experimental mobile projects include Dana Wallet, Silentium, and BlindBit Desktop.

While the bandwidth requirement appears manageable for mobile connections, the security model still hinges on the trustworthiness and completeness of external indexers.