[0xWilliam]

Here are some points to consider as to whether blockchain is appropriate for your application:

Data on blockchains is by default, unencrypted, especially data that needs to be validated by the nodes. Blockchains do not have inherent security against read access. You can control read access to some degree by encrypting certain elements on your blockchain but this can be compromised. Not all information on the blockchain is true; data still needs to be checked and uploaded correctly and as such is open to human error. No amount of time guarantees something will stay in the ledger. It is also difficult to remove data if required by law. It’s not secure because it depends on the assumption that the blockchain community has more compute than the rest of the world. It’s absurdly expensive to mine blocks to store data indefinitely. Lack of government regulations for blockchain could impede growth.

[ThrustVectoring]

>It is also difficult to remove data if required by law.

How difficult is it to introduce illegal data into, say, Bitcoin's blockchain?

[duskwuff]

The same as it'd cost to store any other data -- roughly 380 satoshis (~6.4 cents) per byte, plus various overheads to make it into a a valid transaction.

[dorfsmay]

"It’s absurdly expensive to mine blocks to store data indefinitely."

Is this true of all block chains or specific to bitcoin?

[TheDong]

If you don't have mining, or a similar way to decide between various possible forks, what you have is a cryptographically secured append-only ledger (such as what the git data-format resembles).

That's not a blockchain and that idea has existed for decades already.

I think that idea is now being called a "blockchain" since in reality the trustless/proof-of-work nature of a true blockchain is largely wasted for specific companies.

[tscs37]

It's a blockchain if you have a directed linked list of blocks. Even git is to some extent blockchain.

[TheDong]

That's a redefinition of what a blockchain is IMO.

That's definitely the definition some companies are operating under.. but really?

WALs and journals have existed for ages and both fit the definition of a directed list of blocks.

Hell, ext2 and FAT fit that definition (inodes forming a directed list of block-references).

I guess we all store our data on something that's technically a blockchain by your definition.

[tscs37]

It's not a redefinition, it's a definition that has been around since the 1990's [0], the only requirement for a blockchain is A) directed linked list (block points to previous block) and B) cryptographic security (use hashes as block index)

Bitcoin is merely the first application to use Blockchain in a decentralized proof-of-work manner.

[jacquesm]

A git repository is a Merkle tree.

http://en.wikipedia.org/wiki/Merkle_tree

A bitcoin blockchain is also a Merlke tree.

But a git repository is not a blockchain.

[TheDong]

You didn't include the reference link. The term "blockchain", as used these days, refers to the distributed system underlying cryptocurrencies.

That's not a thing that has existed since the 90s nor is it a thing with so few requirements.