Unless you have a firewall to block normal internet traffic, and only allow tor traffic to go through.
In that case, even if your box gets compromized, there is no way of launching a side-channel attack.
xeniar writes: Alternative currencies have become a popular topic in the Bitcoin space. We have Litecoin and Primecoin introducing alternative mining algorithms with novel properties, PPCoin replacing mining entirely with a non-costly alternative, Ripple creating a cryptocurrency network that can store credit relationships and user-defined currencies, and over seventy more up and running with new ones being created every week. One particularly interesting project that has received a large amount of attention over recent months, however, is Mastercoin. The key difference in Mastercoin is this: rather than trying to bootstrap an entirely new blockchain, as every other cryptocurrency does, Mastercoin seeks to create an entirely new network of currencies, commodities and securities on top of Bitcoin itself.