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@ -17,7 +17,7 @@ networks are inherently resilient, decentralized, and open. A preeminent
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example of a P2P network architecture was the early internet itself,
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where nodes on the IP network were equal. Today's internet architecture
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is more hierarchical, but the Internet Protocol still retains its
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flat-topology essence. Beyond bitcoin, the largest and most successful
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flat-topology essence. Beyond Bitcoin, the largest and most successful
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application of P2P technologies is file sharing, with Napster as the
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pioneer and BitTorrent as the most recent evolution of the architecture.
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@ -29,16 +29,16 @@ that can only be achieved and maintained by a flat, decentralized P2P
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consensus network.
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((("Bitcoin network", "defined")))The term "Bitcoin network" refers to
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the collection of nodes running the bitcoin P2P protocol. In addition to
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the bitcoin P2P protocol, there are other protocols such as Stratum that
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the collection of nodes running the Bitcoin P2P protocol. In addition to
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the Bitcoin P2P protocol, there are other protocols such as Stratum that
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are used for mining and lightweight or mobile wallets. These additional
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protocols are provided by gateway routing servers that access the
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Bitcoin network using the bitcoin P2P protocol and then extend that
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Bitcoin network using the Bitcoin P2P protocol and then extend that
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network to nodes running other protocols. For example, Stratum servers
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connect Stratum mining nodes via the Stratum protocol to the main
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Bitcoin network and bridge the Stratum protocol to the bitcoin P2P
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Bitcoin network and bridge the Stratum protocol to the Bitcoin P2P
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protocol. We use the term "extended Bitcoin network" to refer to the
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overall network that includes the bitcoin P2P protocol, pool-mining
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overall network that includes the Bitcoin P2P protocol, pool-mining
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protocols, the Stratum protocol, and any other related protocols
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connecting the components of the Bitcoin system.
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@ -46,7 +46,7 @@ connecting the components of the Bitcoin system.
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((("Bitcoin network", "node types and roles",
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id="BNnode08")))((("Bitcoin nodes", "types and roles",
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id="BNtype08")))Although nodes in the bitcoin P2P network are equal,
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id="BNtype08")))Although nodes in the Bitcoin P2P network are equal,
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they may take on different roles depending on the functionality they are
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supporting. A Bitcoin node is a collection of functions: routing, the
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blockchain database, mining, and wallet services. A full node with all
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@ -76,7 +76,7 @@ function is indicated by a circle called "Full Blockchain" or the letter
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"B." In <<bitcoin_network>>, SPV nodes are drawn without the "B" circle,
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showing that they do not have a full copy of the blockchain.
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((("bitcoin nodes", "mining nodes")))((("mining and consensus", "mining
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((("Bitcoin nodes", "mining nodes")))((("mining and consensus", "mining
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nodes")))((("Proof-of-Work algorithm")))((("mining and consensus",
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"Proof-of-Work algorithm")))Mining nodes compete to create new blocks by
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running specialized hardware to solve the Proof-of-Work algorithm. Some
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@ -103,12 +103,12 @@ Bitcoin network.
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((("", startref="BNnode08")))((("", startref="BNtype08")))((("Bitcoin
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network", "extended network activities")))The main Bitcoin network,
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running the bitcoin P2P protocol, consists of between 5,000 and 8,000
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listening nodes running various versions of the bitcoin reference client
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running the Bitcoin P2P protocol, consists of between 5,000 and 8,000
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listening nodes running various versions of the Bitcoin reference client
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(Bitcoin Core) and a few hundred nodes running various other
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implementations of the bitcoin P2P protocol, such as Bitcoin Classic,
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implementations of the Bitcoin P2P protocol, such as Bitcoin Classic,
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Bitcoin Unlimited, BitcoinJ, Libbitcoin, btcd, and bcoin. A small
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percentage of the nodes on the bitcoin P2P network are also mining
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percentage of the nodes on the Bitcoin P2P network are also mining
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nodes, competing in the mining process, validating transactions, and
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creating new blocks. Various large companies interface with the Bitcoin
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network by running full-node clients based on the Bitcoin Core client,
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@ -117,9 +117,9 @@ mining or wallet functions. These nodes act as network edge routers,
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allowing various other services (exchanges, wallets, block explorers,
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merchant payment processing) to be built on top.
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The extended Bitcoin network includes the network running the bitcoin
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The extended Bitcoin network includes the network running the Bitcoin
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P2P protocol, described earlier, as well as nodes running specialized
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protocols. Attached to the main bitcoin P2P network are a number of pool
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protocols. Attached to the main Bitcoin P2P network are a number of pool
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servers and protocol gateways that connect nodes running other
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protocols. These other protocol nodes are mostly pool mining nodes (see
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<<mining>>) and lightweight wallet clients, which do not carry a full
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@ -140,14 +140,14 @@ image::images/mbc2_0803.png["BitcoinNetwork"]
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=== Bitcoin Relay Networks
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((("Bitcoin network", "Bitcoin Relay Networks")))((("relay
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networks")))While the bitcoin P2P network serves the general needs of a
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networks")))While the Bitcoin P2P network serves the general needs of a
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broad variety of node types, it exhibits too high network latency for
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the specialized needs of bitcoin mining nodes.
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the specialized needs of Bitcoin mining nodes.
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((("propagation", "relay networks and")))Bitcoin miners are engaged in a
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time-sensitive competition to solve the Proof-of-Work problem and extend
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the blockchain (see <<mining>>). While participating in this
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competition, bitcoin miners must minimize the time between the
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competition, Bitcoin miners must minimize the time between the
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propagation of a winning block and the beginning of the next round of
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competition. In mining, network latency is directly related to profit
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margins.
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@ -176,7 +176,7 @@ at Cornell University. Falcon uses "cut-through-routing" instead of
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they are received rather than waiting until a complete block is
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received.
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Relay networks are not replacements for bitcoin's P2P network. Instead
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Relay networks are not replacements for Bitcoin's P2P network. Instead
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they are overlay networks that provide additional connectivity between
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nodes with specialized needs. Like freeways are not replacements for
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rural roads, but rather shortcuts between two points with heavy traffic,
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@ -194,13 +194,13 @@ irrelevant; the Bitcoin network topology is not geographically defined.
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Therefore, any existing Bitcoin nodes can be selected at random.
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To connect to a known peer, nodes establish a TCP connection, usually to
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port 8333 (the port generally known as the one used by bitcoin), or an
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port 8333 (the port generally known as the one used by Bitcoin), or an
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alternative port if one is provided. Upon establishing a connection, the
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node will start a "handshake" (see <<network_handshake>>) by
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transmitting a +version+ message, which contains basic identifying
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information, including:
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+nVersion+:: The bitcoin P2P protocol version the client "speaks" (e.g., 70002)
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+nVersion+:: The Bitcoin P2P protocol version the client "speaks" (e.g., 70002)
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+nLocalServices+:: A list of local services supported by the node, currently just +NODE_NETWORK+
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+nTime+:: The current time
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+addrYou+:: The IP address of the remote node as seen from this node
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@ -223,7 +223,7 @@ addresses of Bitcoin nodes. Some of those DNS seeds provide a static
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list of IP addresses of stable Bitcoin listening nodes. Some of the DNS
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seeds are custom implementations of BIND (Berkeley Internet Name Daemon)
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that return a random subset from a list of Bitcoin node addresses
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collected by a crawler or a long-running bitcoin node. The Bitcoin Core
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collected by a crawler or a long-running Bitcoin node. The Bitcoin Core
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client contains the names of five different DNS seeds. The diversity of
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ownership and diversity of implementation of the different DNS seeds
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offers a high level of reliability for the initial bootstrapping
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@ -337,7 +337,7 @@ startref="BNextend08")))((("", startref="BNodiscover08")))
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clients")))((("blockchain (the)", "full blockchain nodes")))Full nodes
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are nodes that maintain a full blockchain with all transactions. More
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accurately, they probably should be called "full blockchain nodes." In
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the early years of bitcoin, all nodes were full nodes and currently the
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the early years of Bitcoin, all nodes were full nodes and currently the
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Bitcoin Core client is a full blockchain node. In the past two years,
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however, new forms of Bitcoin clients have been introduced that do not
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maintain a full blockchain but run as lightweight clients. We'll examine
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@ -355,7 +355,7 @@ receive updates about new blocks of transactions, which it then verifies
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and incorporates into its local copy of the blockchain.
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((("Bitcoin nodes", "full nodes")))Running a full blockchain node gives
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you the pure bitcoin experience: independent verification of all
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you the pure Bitcoin experience: independent verification of all
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transactions without the need to rely on, or trust, any other systems.
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It's easy to tell if you're running a full node because it requires more
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than one hundred gigabytes of persistent storage (disk space) to store
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@ -534,7 +534,7 @@ user of that wallet, destroying the user's privacy.
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.SPV node synchronizing the block headers
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image::images/mbc2_0807.png["SPVSynchronization"]
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Shortly after the introduction of SPV/lightweight nodes, bitcoin
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Shortly after the introduction of SPV/lightweight nodes, Bitcoin
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developers added a feature called _bloom filters_ to address the privacy
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risks of SPV nodes. Bloom filters allow SPV nodes to receive a subset of
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the transactions without revealing precisely which addresses they are
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@ -747,12 +747,12 @@ client.
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((("Bitcoin network", "encrypted
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connections")))((("encryption")))((("authentication")))Most new users of
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bitcoin assume that the network communications of a Bitcoin node are
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Bitcoin assume that the network communications of a Bitcoin node are
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encrypted. In fact, the original implementation of bitcoin communicates
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entirely in the clear. While this is not a major privacy concern for
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full nodes, it is a big problem for SPV nodes.
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As a way to increase the privacy and security of the bitcoin P2P
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As a way to increase the privacy and security of the Bitcoin P2P
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network, there are two solutions that provide encryption of the
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communications: _Tor Transport_ and _P2P Authentication and Encryption_
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with BIP-150/151.
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@ -814,7 +814,7 @@ privacy of the SPV client.
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Additionally, authentication can be used to create networks of trusted
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Bitcoin nodes and prevent Man-in-the-Middle attacks. Finally, P2P
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encryption, if deployed broadly, would strengthen the resistance of
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bitcoin to traffic analysis and privacy-eroding surveillance, especially
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Bitcoin to traffic analysis and privacy-eroding surveillance, especially
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in totalitarian countries where internet use is heavily controlled and
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monitored.
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David A. Harding
1 year ago