Sia
Sia is a storage market built around renters, hosts, and file contracts. Renters encrypt and erasure-code files, split them into shards, and distribute those shards across hosts. File contracts define payment and storage obligations.
Key mechanics:
- Client-side encryption before upload.
- Erasure coding across hosts.
- File contracts on the Sia blockchain.
- Host collateral and proofs.
- Renter software manages host selection, repair, and renewals.
Sia is attractive when the user wants low-cost decentralized backup and is willing to run or trust renter software that manages contracts and repair.
Storj
Storj is decentralized object storage with a more managed user experience. Data is encrypted client-side, split into pieces, erasure-coded, and distributed across storage nodes. Users interact through S3-compatible tooling and Storj's satellite coordination layer.
Key mechanics:
- Client-side encryption.
- Erasure coding and distribution across nodes.
- Satellites coordinate metadata, node reputation, billing, and audits.
- S3-compatible gateway options for application compatibility.
Storj is less trust-minimized than the purest P2P designs because satellites coordinate substantial control-plane behavior, but the operational experience is closer to production cloud storage.
Comparison
| Dimension | Sia | Storj |
|---|---|---|
| User model | Renter contracts | Managed object storage |
| Coordination | Blockchain + renter software | Satellites |
| Privacy | Client-side encryption | Client-side encryption |
| Availability | Erasure coding + repair | Erasure coding + audits |
| UX | More self-managed | More S3-like |
| Best fit | Sovereign backup | App object storage |
When To Use
| Goal | Better fit |
|---|---|
| Lowest-cost encrypted backup | Sia |
| S3-compatible decentralized storage | Storj |
| Maximum self-custody of storage workflow | Sia |
| Application developer ergonomics | Storj |
| Immutable public archive | Arweave instead |
| Content-addressed public distribution | IPFS and Filecoin instead |
Trade-offs
Strengths
- Client-side encryption is central to both designs.
- Erasure coding reduces dependence on any single host.
- Cheaper than hyperscaler storage for some workloads.
- Better fit for backups than IPFS alone.
Limitations
- Recovery depends on renter keys and metadata.
- Repair and renewal are operational responsibilities.
- Gateways and coordination services can become practical choke points.
- Neither system gives the same public-verifiability story as content-addressed storage unless hashes are published separately.
Attack Surface
| Attack | Mitigation |
|---|---|
| Storage node disappears | Erasure coding, repair, multiple hosts |
| Node serves corrupt shard | Cryptographic integrity checks |
| Metadata loss | Back up renter metadata and keys |
| Coordination-layer outage | Keep local client state; use multiple access paths where possible |
| Plaintext compromise | Keep encryption client-side; never upload raw secrets |
| Host collusion | Wide shard distribution and provider diversity |
Primary sources
- Sia: Simple Decentralized Storage
- Sia documentation
- Storj: A Decentralized Cloud Storage Network Framework
- Storj: encryption
- Storj documentation
For another encrypted storage design, see Tahoe-LAFS. For a device-based setup, follow Private File Sync and Backup.
Page history
- Updated
- 2026-10-25
- Origin
- Compiled from the ungovernable.tech research notes.
- Improve this page
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