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---
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layout: core
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permalink: /:collection/:path.html
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---
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# Naming system feature comparison
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{:.no_toc}
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BNS is not the only naming system in wide-spread use, nor is it the only
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decentralized naming system that implements human-readable, globally-unique, and
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strongly-owned names. This page describes some other naming systems in
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comparison to Blockstack:
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* TOC
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{:toc}
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## Blockstack vs DNS
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Blockstack and DNS both implement naming systems, but in fundamentally
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different ways. Blockstack *can be used* for resolving host names to IP
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addresses, but this is not its default use-case. The [Blockstack Naming
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Service]({{ site.baseurl }}/core/naming/introduction.html) (BNS) instead behaves
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more like a decentralized
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[LDAP](https://en.wikipedia.org/wiki/Lightweight_Directory_Access_Protocol) system for
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resolving user names to user data.
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While DNS and BNS handle different problems, they share some terminology and
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serialization formats. However, it is important to recognize that this is the
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*only* thing they have in common---BNS has fundamentally different semantics
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than DNS:
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* **Zone files**: Blockstack stores a DNS zone file for each name. However,
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the semantics of a BNS zone file are nothing like the semantics of a DNS zone
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file---the only thing they have in common is their format.
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A "standard" Blockstack zone files only have `URI` and `TXT` resource records
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that point to the user's application data. Moreover, a Blockstack ID has a
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*history* of zone files, and historic zone files can alter the way in which a
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Blockstack ID gets resolved (DNS has no such concept). It is conceivable that an advanced
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user could add `A` and `AAAA` records to their Blockstack ID's zone file,
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but these are not honored by any Blockstack software at this time.
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* **Subdomains**: Blockstack has the concept of a subdomain, but it is
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semantically very different from a DNS subdomain. In Blockstack, a subdomain
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is a Blockstack ID whose state and transaction history are anchored to the
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blockchain, but stored within an on-chain Blockstack ID's zone file history.
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Unlike DNS subdomains, a BNS subdomain has
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its own owner and is a first-class BNS name---all subdomains are resolvable,
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and only the subdomain's owner can update the subdomain's records. The only thing BNS subdomains and DNS
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subdomains have in common is the name format (e.g. `foo.bar.baz` is a subdomain
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of `bar.baz` in both DNS and BNS).
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More details can be found in the [Blockstack vs
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DNS]({{ site.baseurl }}/core/naming/comparison.html) document. A feature
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comparison can be found at the end of the [Blockstack Naming
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Service]({{ site.baseurl }}/core/naming/introduction.html) document.
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## Blockstack vs Namecoin
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Namecoin also implements a decentralized naming service on top of a blockchain,
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just like BNS. In fact, early versions of Blockstack were built on Namecoin.
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However, [it was discovered](https://www.usenix.org/node/196209) that Namecoin's
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merged mining with Bitcoin regularly placed it under the *de facto* control of a single
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miner. This prompted a re-architecting of the system to be *portable* across
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blockchains, so that if Blockstack's underlying blockchain (currently Bitcoin)
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ever became insecure, the system could migrate to a more secure blockchain.
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A feature comparison can be found at the end of the [Blockstack Naming
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Service]({{ site.baseurl }}/core/naming/introduction.html) document.
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## Blockstack vs ENS
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ENS also implements a decentralized naming system on top of a blockchain, but as
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a smart contract on Ethereum. Like BNS, ENS is geared towards resolving names
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to off-chain state (ENS names resolve to a hash, for example). Moreover, ENS is
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geared towards providing programmatic control over names with Turing-complete
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on-chain resolvers.
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BNS has a fundamentally different relationship with blockchains than ENS.
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Whereas ENS tries to use on-chain logic as much as possible, BNS
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tries to use the blockchain as little as possible. BNS only uses it to store a
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database log for name operations (which are interpreted with an off-chain BNS
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node like Blockstack Core). BNS name state and BNS subdomains reside entirely
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off-chain in the Atlas network. This has allowed BNS to migrate from blockchain
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to blockchain in order to survive individual blockchain failures, and this has
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allowed BNS developers to upgrade its consensus rules without having to get the
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blockchain's permission (see the [virtualchain
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paper](https://blockstack.org/virtualchain.pdf) for details).
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## Summary feature comparison
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The following feature table provides a quick summary how BNS differs from other naming systems
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| Feature | BNS | [ENS](https://ens.domains/) | DNS | [Namecoin](https://namecoin.org/) |
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|----------------------------|-----|-----|-----|----------|
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| Globally unique names | X | X | X | X |
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| Human-readable names | X | X | X | X |
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| Strongly-owned names | X | X | | X |
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| Names are enumerable | X | | | X |
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| Registration times | 1-2 hours | ~1 week | ~1 day | 1-2 hours |
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| Subdomain registration times | 1 hour (instant with [#750](https://github.com/blockstack/blockstack-core/issues/750)) | varies | instant | ~1 hour |
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| Anyone can make a TLD/namespace | X | [1] | | [1] |
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| TLD/Namespace owners get registration fees | X | | X | |
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| TLD/Namespace can be seeded with initial names | X | | X | |
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| Portable across blockchains | X | | N/A | |
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| Off-chain names | X | | N/A | |
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| Off-chain name state | X | X | N/A | |
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| Name provenance | X | X | | X |
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| [DID](http://identity.foundation) support | X | | | |
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| Turing-complete namespace rules | | X | X | |
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| Miners are rewarded for participating | [1] | | N/A | X |
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[1] Requires support in higher-level applications. These systems are not aware
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of the existence of namespaces/TLDs at the protocol level.
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[2] Blockstack Core destroys the underlying blockchain token to pay for
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registration fees when there is no pay-to-namespace-creator address set in the
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name's namespace. This has the effect of making the blockchain miners' holdings
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slightly more valuable.
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