Refusing Incoming Connections

The success probability of double-spending attacks on zero-confirmation transactions heavily depends on the propagation delay of TRy from A to V. Clearly, a direct communication channel between A and V considerably contributes to the success of the attack. For instance, if merchants do not accept incoming connections or are located behind firewalls and NATs, then the success probability of doublespending attacks can be reduced.

Note that it is hard, however, for merchants to ensure that all their current connections are trustworthy. For example, their connections can be compromised by the adversary.

Increasing the Number of Neighbors

We additionally point out that the number of connections established by V is an important parameter affecting the success of double-spending attacks. That is, the fewer connections of V, the more likely is that all the neighbors of V receive TRy before TRa and thus that V does not receive TRa and therefore cannot detect the attack. Similarly, as the number of connections of V increases, it is more likely that [1]

Table 4.4

Experimental Detection Probability Using 5 Observers 7

Setting

% Observed

Europe, 8 connections, 3 helpers

53%

Europe, 8 connections, 3 helpers

47%

South America, 8 connections, 2 helpers

62%

Asia Pacific, 8 connections, 2 helpers

91%

North America, 20 connections, 5 helpers

46%

North America, 20 connections, 5 helpers

74%

North America, 20 connections, 1 helper

78%

North America, 20 connections, 4 helpers

78%

North America, 20 connections, 2 helpers

60%

North America, 20 connections, 1 helper

60%

Europe, 20 connections, 3 helpers

87%

Europe, 30 Connections, 1 helper

42%

Asia Pacific, 40 connections, 1 helper

42%

Europe, 40 connections, 1 helper

36%

Europe, 40 connections, 2 helpers

36%

South America, 40 connections, 1 helper

57%

Asia Pacific, 80 connections, 1 helper

18%

Europe, 80 connections, 1 helper

28%

Asia Pacific, 100 connections, 1 helper

88%

some of these neighbors receive TRa before TRy and forward it to V, who can immediately detect a double-spending attempt.

  • [1] In this case, V cannot detect double-spending attacks even if it adopts a very large listening period.Here, ‘Setting’ refers to the location of V, the number of connections of V at the time of the attack,and the number of helpers employed by A.
 
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