Possible way for a supernode to learn the stem

[amiller]

As of 66d0cf2, if a node receives an DINV(tx) corresponding to a tx already under embargo, then embargo ends immediately and the transaction is propagated like usual in "fluff" mode. This is intended to help handle "cycles" gracefully without the transaction getting stuck.

However, this leads to a possible strategy for a supernode to identify the nodes involved in a stem. Upon receiving a stem message DTX(tx), the attacker could send DTX(tx) to every node. For nodes that already have the stem, this would certainly cause them to "fluff" immediately; for nodes that don't, they would fluff with only 0.1 probability.

A mitigation would be to handle cycles a different way... enter fluff mode upon receiving a DINV from the same peer a second time. This would require storing some additional data somewhere (right now we forget who told us about the tx).