Light clients and privacy
- Author
- CRYPTO PORT Editorial
- Published
- Updated
- Reading time
- 4 min
In short
A light client does not store the whole chain; it asks an external server for the parts it needs. Those queries name your addresses, so the server learns your balances and what you care about. Convenience here is paid for by handing information to a single provider.
Key points
- Holds no full copy and queries an external server instead
- Those queries include your own addresses
- The responder can see your balances and activity
- It may be logged together with your IP address
Definition
A client that keeps only block headers and the transactions it needs, fetching the rest from outside. The content of its queries tells the responding party which addresses the user cares about.
A full history runs to hundreds of gigabytes, which no phone can carry. A light client sidesteps this by verifying only block headers and fetching just the transactions that concern it. Synchronisation is fast and storage stays small.
The price is in the queries themselves. Asking for transactions relating to an address necessarily tells the responder which addresses interest you. Asking about several at once also reveals that they belong to the same user. Logged alongside your IP, the association becomes considerably stronger.
Technical responses exist: distributing per-block filters so the device does the matching locally, and research into cryptographically hiding the queries. Because implementations differ enormously in what they reveal, it is worth checking which approach your wallet takes.
Watch out for
- · The faster a wallet shows balances, the more likely it leans on an external server
- · Querying several addresses together reveals them as one user's holdings
- · Even free services differ widely in how they handle usage logs