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I have seen these two words - private and permissioned, a lot. Sometimes, they're used interchangeably. I don't believe these words have the same meaning. Can anyone give a detailed description differentiating these two types of blockchains?

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They are definitely not used interchangeably since they have a very different meaning/purpose:

Private blockchains are private because of the genesis block they are using. Their blocks do not match with any other blockchains (you cannot link blocks from the main net to blocks of a private net with a different genesis blocks as the block header hashes won't match).

Note that any node can connect to a private blockchain if it knows a bootstrap node address to sync, the network id, and the genesis file. This node can perform any action on the private net; mine, make transactions, deploy contracts, etc.

Permissioned blockchains on the other hand offer an access control mechanism so that peers are allowed or rejected based on a control value (an address, a certificate, etc.).

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Private Blockchain

Is a blockchain, where we allow only known nodes to participate in the network. Ideally, it is internal for an organisation, a bank per se.

Permissioned Blockchain

The first primary difference between a properly conceived permissioned blockchain network and an unpermissioned blockchain network is whether the participants in the network have an ability to restrict who can participate in the consensus mechanism of the blockchain’s network.

Is a blockchain where we can allow certain actions to be performed only by certain addresses (wallets)

Source

  1. docs.erisindustries.com
  2. bitcoinmagazine.com
  3. lightrains.com
  • There doesn't seem much difference between your two definitions. In both cases, it seems control over participation is the key characteristic. Can you expand further on the differences? – Duncan Jones Jan 2 '18 at 9:23
  • @DuncanJones yes, participation and data privacy differentiate these two. – niksmac Jan 2 '18 at 16:42
  • same here, my question is probably really how are access control implemented, is it centralized auth? if so, how is it really more secure than a centralized arch (instead of blockchain) in the first place? – Justin Zhang Mar 24 '18 at 16:03
  • i mean there are a lot of archs, like CDN / multi-region cloud, that looks discentralized but are really centralized because their auth is centralized. so if the auth is centralized here, then how could it be called discentralized at all? if the auth is discentralized, can you point to some reference for that? – Justin Zhang Mar 24 '18 at 16:07

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