Is blockchain always "public"?

Question

Is the following definition of blockchain by its wikipwdia page correct?

Where it is mentioned:

A blockchain is a decentralized, distributed and public digital ledger ...

Cannot we have a private blockchain? And if so, is the above proposition wrong ? when it says always a blockchain is public.

An example: Consider a company or organization which aims at using (permissioned) blockchain such that it is visible only for its (internal) employees. So, it uses ex. visibility property of blockchain but limited only to internal employees.

Please Note that here the question is NOT if using a permissioned blockchain is logical or not, but also the question is the exact definition of a blockchain. So, according to definition of blockchain in its wikipedia page, a permissioned blockchain is real blockchain?

From my point of view: to have a blockchain with immutable transactions history, we need the blockchain to be maintained by a decentralized consensus, otherwise in case of using ex. PoA or permissioned approach, since it's a centralized approach, there is no guarantee for a blockchain user that in future what happens for the blockchain and if the blockchain will exist after years? So, in this case, there is no guarantee for existing transactions history in future. And at this point question is why do we use such a blockchain?

Answer 1

Yes and no...

Yes because a the data in a blockchain is persisted on every node on the blockchain, this therefore makes this data public. There are however ways of encrypting the data to make it "public"(comprehensible) to only the people who have the key to decrypt the data.

Can we have a private blockchain? Absolutely yes. The the ledger/data would be made visible only to the private members. Also running a node on this blockchain would require that you be a member of this private blockchain. Meaning there will be some sought of permission that one would need from the private members to participate in this blockchain. An example of an application of the private blockchain would be a blockchain that helps efficient and transparent data/informaton transfer in an organisation.

The preposition is not wrong as the ledger is still public to the private members. Hope this helps.