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52 lines
2.4 KiB
Markdown
52 lines
2.4 KiB
Markdown
An evaluation of the Sia whitepaper
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2020-12-07 Mark Spanbroek
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https://sia.tech/sia.pdf
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Goal of this evaluation is to find things to adopt or avoid while designing
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Dagger. It is not meant to be a criticism of Sia.
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#### Pros:
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+ Clients do not need to actively monitor hosts (§1). Once a contract has been
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agreed upon, the host earns/loses coins based on proofs of storage that the
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network can check.
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+ Denial of service attacks can be mitigated by burning funds associated with
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missed proofs (§4).
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+ Proof of storage is simple; provide a random piece of the file, and the
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corresponding Merkle proof (§5.1).
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+ Promotes erasure codes to safeguard against data loss (§7.2).
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+ Suggests to use payment channels for micro-payments (§7.3).
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+ The basic reputation system is protected against Sybil attacks (§7.4).
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#### Cons:
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- Sia has its own blockchain (§1), which makes some attacks more likely
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(§5.2, §5.3). This can be mitigated by adopting a widely used, general purpose
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blockchain such as Ethereum.
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- Requires a multi-signature scheme (§2).
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- The proof-of-storage algorithm requires that hosts store the entire file (§4),
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instead of a few chunks.
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- Contracts can be edited (§4). This feels like an unnecessary complication of
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the protocol.
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- Randomness for the storage proofs comes from the latest block hash (§5.1).
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This can be manipulated, especially when using a specialized blockchain for
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storage.
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- There is an arbitrary data field that might be used for advertisements in a
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storage marketplace (§6). This feels like a very restrictive environment for a
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marketplace, and an unnecessary complication for the underlying blockchain.
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- It is suggested that clients use erasure coding before encryption (§7.2). If
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this were reversed (first encryption, then erase coding) then this would open
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up scenario's for caching and re-hosting by those who do not possess the
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decryption key.
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- Consecutive micropayments are presented as a solution for the trust problems
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while downloading (§7.3). This assumes that the whole file, or a large part of
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it, is stored on a single host. It also doesn't entirely mitigate withholding
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attacks.
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- The basic reputation system favors hosts that have already earned or bought
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coins (§7.4). It is also unclear how the reputation system discourages abuse.
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- Governance seems fairly centralized, with most funds and proceeds going to a
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single company (§8).
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