Page 32 - FIGI: Security Aspects of Distributed Ledger Technologies

Norms for Routing Security (MANRS), a commu- spending attacks, waste mining power of other
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nity initiative of network operators and Internet miners. 203
Exchange Points that creates a baseline of security
expectations for routing security. Risks:
The attacker can exploit the victim for attacks on
Specific Threat: Sybil Attack� bitcoin’s mining and consensus system, including
In a Sybil attack the attacker controls or assumes double spending, selfish mining, and adversarial
multiple virtual identities or nodes which is also a forks in the DL.
fact unknown to the network, e.g. multiple nodes
surrounding a target containing different, front facing Mitigation and Recommendations:
aliases of the attacker. On a blockchain network the Mitigation procedures include the use of whitelisting
attacker creates numerous fake identities to impact procedures, diversify incoming connections instead
how good nodes act or are prevented from acting. of relying upon a limited number or the same IP
address, among multiple other mitigants. 204
Risks:
Can potentially result in an attempt to create a 8.3.5 Issue: Duplication of Transactions
dominance/51% attack (and create double spending
opportunities), prevent the relay of messages to the Specific Threat: Double-Spending Attacks
rest of the network; commit bad acts such as ‘spam-
ming the network’ with controlled nodes to subvert Dimensions Affected: Network, Consensus, Data
the reputation system. Model
Blockchain technologies operate decentralized,
Mitigation and Recommendations: distributed manner. Transactions are generated and
propagated throughout a network of validating
• Cost-based prevention, e.g. consensus algorithms nodes, potentially global. Using a consensus mech-
make it expensive to perpetrate a Sybil attack, e.g. anism, a validator broadcasts to other validators its
POW requires the attacker to own and provide confirmation of the validity of a block of transactions,
power to each alias or amount needed to stake to which is relayed to other network nodes for reaching
engage in voting or delegation of witnesses who consensus on adding the block to the blockchain.
validate transactions. The time it takes to perform this process creates a
• Use of a ‘mixing protocol’ such as Xim which is vector for attacks on verification mechanisms.
also a cost-based prevention mechanism. This could include a ‘double-spending’ attack,
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• Use of a reputation system and/or validation which occurs when an attacker uses or ‘spends’ the
200
techniques such as a lookup at a central author- same digital currency or tokens for multiple trans-
ity or trust gained from experience such as prior actions. On many blockchain systems, especial-
205
interaction. ly POW-based blockchains, a transaction does not
complete and finalize in real time but only after a cer-
Specific Threat: Eclipse Attack tain duration. A transaction is submitted and propa-
When an attacker is able to control a sufficient number gated to nodes across a network, potentially distant,
of nodes surrounding the target and prevents it from which process, confirming, reach consensus and add
being sufficiently connected (ingoing and outgoing) a new transaction to the blockchain. An attacker can
to the network (such as being eclipsed from being exploit this intermediate time 206
seen by the sun.) The use of botnets can increase These threats may follow from one or more of the
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success rate. following attack types:
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Vulnerability: • Race: An attacker makes a purchase from a mer-
This attack may allow an adversary controlling a chant who accepts unconfirmed transactions and
sufficient number of IP addresses to monopolize ships goods immediately upon or shortly after
all connections to and from a victim bitcoin node. seeing the transaction occur. Concurrently, the
This attack can potentially trigger a 51%/dominance attacker submits a second double spend trans-
vulnerability, cause repercussions similar to DDoS action to the network which results in a race for
attacks, shield the node from view of the blockchain the second transaction to be confirmed before the
and cause inconsistencies and potential for double first or the second transaction to be confirmed in

30 Security Aspects of Distributed Ledger Technologies