E018 – Tech Spec – Sia, ultimate blockchain file storage

What if you could store your data in the cloud, encrypted, for a fraction of the cost of Amazon S3, Google, or Azure? With Sia, a decentralized file storage solution that leverages blockchain, you can. Learn more about how it works in this episode.

Blockchain Overview

A blockchain is a permissionless distributed database that maintains a continuously growing list of transactional data records. The system’s design means it is hardened against tampering and revision, even by operators of the nodes that store data. The initial and most widely known application of the block chain technology is the public ledger of transactions for bitcoin, but its structure has been found to be highly effective for other financial vehicles.

CONSENSUS BUILDING The ability for a significant number of nodes to converge on a single consensus of the most up-to-date version of a large data set such as a ledger TRANSACTION VALIDITY The ability for any node that creates a transaction to determine whether the transaction is valid, able to take place, and become final (i.e. that there were no conflicting transactions) AUTOMATED RESOLUTION An automated form of resolution that ensures that conflicting transactions (such as two or more attempts to spend the same balance in different places) never become part of the confirmed data set.

Blockchain block detail

[Illustration by Matthäus Wander (Wikimedia)]

  • Timestamp: The time when the block was found.
  • Reference to Parent (Prev_Hash): This is a hash of the previous block header which ties each block to its parent, and therefore by induction to all previous blocks. This chain of references is the eponymic concept for the blockchain.
  • Merkle Root (Tx_Root): The Merkle Root is a reduced representation of the set of transactions that is confirmed with this block. The transactions themselves are provided independently forming the body of the block. There must be at least one transaction: The Coinbase. The Coinbase is a special transaction that may create new bitcoins and collects the transactions fees. Other transactions are optional.
  • Target: The target corresponds to the difficulty of finding a new block. It is updated every 2016 blocks when the difficulty reset occurs.
  • The block’s own hash: All of the above header items (i.e. all except the transaction data) get hashed into the block hash, which for one is proof that the other parts of the header have not been changed, and then is used as a reference by the succeeding block.

Why You Can't Cheat at Bitcoin 2. But one miner wants to alter a transaction in block 74. 3. He'd haveto make his changes and redo all the computations for blocks 74—90 and do block 91. That's 18 blocks Of expensive computing. I . Say everybody is working on block 91. 4. What's worse, he'd have to do it all before everybody else in the Bitcoin network finished just the one block (number 91) that they're working on.

Sia Overview

  • Decentralized network that places encrypted pieces of your data on dozens of notes
  • Aims to be fastest, cheapest, most secure storage solution and compete with AWS, GCP, Azure
  • Users pay in Siacoins, a cryptocurrency like Bitcoin
    • Must go USD -> Bitcoin -> Siacoin -> Wallet -> File Upload
  • Open source
  • Started by David Vorick and Luke Champine through a VC backed Boston-based company called Nebulous Inc
  • Origins in the HackMIT 2013 conference
  • Uses ASICs (application specific integrated circuits) for mining
    • These are purpose built integrated circuits, not general multi-use devices
    • Evolution from CPU -> GPU – ASIC
    • Faster and less vulnerable to attacks than GPUs
    • Why? See here.
    • Created a company to make ASICs called obelisk.
    • ~$2,500 per machine
  • Current price is about 124 Siacoin to $1USD


  • Decentralized, peer-to-peer
  • Encrypted and immutable
  • Hosts can earn money by renting free disk space to renters
    • Must maintain 95% uptime to preserve collateral

Possible Issues

  • Renters uploading illegal content to hosts
    • However, renters would have to pay for the bandwidth leechers use to download files
  • Slow at this point
  • Low number of users


Deep Sky Blue by Graphiqs Groove


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