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Is there any solid justification that every blockchain is a distributed ledger, but not every distributed ledger is a blockchain?.

What are the main differences between blockchains & distributed ledger technology from a technical perspective?

Why did some researchers say that distributed ledger is different than blockchain, on other side said that blockchain is same as from a technical perspective?

Note: Common keywords for distributed ledger are (shared ledger, or Distributed Ledger Technology, DLT)

I wish if someone could provide a solid justification for it, especially, from the technical perspective not as the definition of the above term.

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    "Why did some researchers say that distributed ledger is different than blockchain" I don't know. Maybe link to something that says that so we can find out?
    – user19510
    Oct 1, 2018 at 16:07
  • I think it's generally something along the lines of: blockchain = DLT + cryptoeconomics. In that private blockchains and blockchain-like platforms which don't use cryptoeconomic incentives to secure themselves are often not considered as pure blockchain platforms by certain parts of the community.
    – Richard Horrocks
    Oct 1, 2018 at 16:19
  • @RichardHorrocks , well, the bank of England announced 1 that it is looking to breathe new life into their Real-Time Gross Settlement (RTGS) system, using both blockchain and distributed ledger technology. However, these words are not interchangeable though, so it’s important that we highlight their differences.
    – Hasan alobadi
    Oct 1, 2018 at 16:30
  • If the Bank of England are using it, it'll likely be a private or consortium network in which cryptoeconomics plays no part. If that's the case, the purists would label it as DLT, rather than "blockchain". I suspect the article uses the two terms interchangeably, either deliberately, because "blockchain" sounds sexier than DLT, or because they're unaware that some people consider them different.
    – Richard Horrocks
    Oct 1, 2018 at 16:36
  • This is a good article to start with. The conclusion discusses the distinction between the two terms: medium.com/l4-media/making-sense-of-cryptoeconomics-c6455776669.
    – Richard Horrocks
    Oct 1, 2018 at 16:42

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This will be a very short summary of a complex topic.

Starting with Bitcoin and Ethereum, the network achieves eventual consensus in the form of a chain of blocks containing transactions in the order the network has decided to process them, a.k.a. a chain of blocks.

This is not the only way to reach eventual consensus. In Corda, for example, transactions are not arranged into blocks.

They use an unspent transaction output (UTXO) model in which unique states exist and transactions consume states to make new states. The implementation is a big departure from a chain of blocks. There are no blocks. There is no chain.

If I'm not mistaken, R3 was among the first to start using the expression "distributed ledger" to describe a system with many similarities to Ethereum and many differences.

I'm not sure DLT is a precise technical term. In my mind, blockchain is one way to achieve a distributed ledger, but there are others.

Hope it helps.

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  • Thank you for your contribution,refer to the document below, they have shown a taxonomy of Distributed Ledger technology, as (Centralized Ledger), (Distributed Ledger permissionless), and (Distributed Ledger permissioned) p7-12.As I understand from this doc that, Distributed Ledger permissionless is a blockchain use in Bitcoin and Ethereum, but the Distributed Ledger permissioned is another type of blockchain use in R3’s Corda,Hyperledger Fabric and so on. my point is that Distributed Ledger and blockchain are not interchangeable words since there is a different technical aspect found in them.
    – Hasan alobadi
    Oct 1, 2018 at 18:03
  • here is the doc [1 (documents.worldbank.org/curated/en/177911513714062215/pdf/…) The thing that makes me confused is during the review of the research papers for my systematic literature review paper--, I have found some researchers are mixed between these two words even some said the Ethereum is Distributed Ledger (permissioned).
    – Hasan alobadi
    Oct 1, 2018 at 18:03
  • There is widespread confusion. I incline to think "membership" - governance, technical implementation, design goals, accountability, etc., is an important property to understand at the implementation level but it's not a great way to categorize the tech itself. Consider that Ethereum can be permissionless or permissioned. Note also that work is underway to bring Corda into a public permissionless setting. How does that tell us if they use chains of blocks or some other type of data structure and consensus process?
    – Rob Hitchens
    Oct 1, 2018 at 19:14
  • In my mind, the data structure, consensus mechanism, membership, and the way contracts are designed and executed are good differentiators to look at on a case-by-case basis. That World Bank doc has some definitions of terms on page IV. They describe blockchain as a data structure that is one of many ways to do a DLT. I can live with that. :-)
    – Rob Hitchens
    Oct 1, 2018 at 19:18
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Okay, I found the main article I was thinking of when I left my comments above. This is an article I've referred to in previous answers where cryptoeconomics was of interest. (For example, this one.)

There is an article from earlier in 2018 written by ConsenSys that looks at the comparison between Blockchain and DLT in detail:

Blockchain vs. Distributed Ledger Technologies (External link.)

There are several key points of comparison in the article, including the difference in the use of cryptoeconomic incentive layers, which I mentioned.

The TL;DR is as follows:

  • "Blockchain" is the label given to those technologies that are operating in an environment where there is little or no trust between transacting parties. In such cases cryptoeconmics comes into play to incentivise participants to remain honest.
  • "DLT" is the label given to those technologies operating where there is a level of trust between participants, such as private or consortium networks. In those cases there's no need (or at least less need) to incentivise transacting parties to be honest, and therefore no requirement to incorporate the game theoretical considerations of blockchains. (i.e. Mechanism design is less important.)

From the article:

"A core tenet that distinguishes blockchain ecosystems from distributed ledger-designed database systems is the capability to use mechanism design as an economic incentive layer that ensures proper allocation of trust and cooperation to make a system behave in a way that is conducive towards instantiating decentralized consensus among users as well as security."

So, for a blockchain platform such as Ethereum:

"An example of cryptoeconomic incentive layers can also be seen in Ethereum’s transition to a proof of stake consensus mechanism via implementations of Casper."

But for a DLT platform, such as R3 or Hyperledger:

"An important note to recognize is that R3 Corda and Hyperledger Fabric do not have these cryptoeconomic incentive layers instantiated within their software architectures. Due to the fact that the software architectures are foundationally designed based on distributed database focused paradigms, they were not originally designed for the incorporation of native cryptocurrency layers within the overall framework."

As Rob mentioned in his answer, this is a complex topic, and my personal interest in cryptoeconomics perhaps skews my opinion of what the most important differences are.

And, finally, while ConsenSys are a well-respected leader in the space, they don't get to define what terms like "blockchain" and "DLT" actually mean. It's likely the World Bank have their own ideas...

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Few additional informations: The terms blockchain and DLT have ambivalent meanings.

From the technical perspective: blockchain is a specific implementation of a DLT.

From the idealogical perspective: blockchain is a label for a "public, unpermissioned, egalitarian"-DLT (in the technical sense). And DLT is a label for "private, permissioned, authoritarian"-DLT

  • private / public – connectivity to the network. E.g.: are nodes accesible via Internet or Intranet? Can anyone join or is it limited to a closed user group?

  • permissioned / unpermissioned – access regulation. Do I need a permission/invitation to join the network?

  • egalitarian / authoritarian – are all participants (potentially) equal in their rights?

There are also different combinations of these three dimensions. For instance, one could also have a "public, permissioned, authoritarian"-DLT like for instance Hedera Hashgraph is trying to establish.

For more details on this perspective, see: http://blockchainers.org/index.php/2018/01/02/is-it-a-blockchain-or-is-it-a-dlt/

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