I am researching the topic of cryptocurrency and its impact on society.
It's often said that cryptocurrency is equivalent to cash, but that is clearly not true since cash is very difficult to transport in large quantities over borders and usually requires physical presence to conduct a trade. It is also said that Bitcoin is not anonymous since the transactions can be tracked. However, in reality, its pseudo-anonymity can easily translate to true anonymity when a good laundry service is employed. Thus, cryptocurrency can and does open new avenues for criminals, such as making it much easier to transport and launder the proceeds of crime, facilitating bribery and blackmail by reducing their risks, and many of the bad things cash is associated with since money has always been a central element in crime.
Regardless of what you think of this from a political point of view (and I expect that many in this community don't see a problem with it), I think there is an interesting technical question here:
Is it possible to design a cryptocurrency that achieves a compromise between the relatively strong pseudo-anonymity of Bitcoin and the classic banking system that is disastrous to personal privacy?
Ideally, we should design a system that keeps as much as possible of Bitcoin's strong privacy protection and other desirable features such as decentralization, but at the same time, allows law enforcement to track anti-social actors like the classic banking system allows.
So, I'm asking for ideas of about how to get the best of both worlds. The network should work in a high privacy mode by default, and when the need arises, law enforcement should be able to reduce the privacy in a very visible way, for example by requesting the collaboration of other users. There should be no backdoor, no way to deanonymize the whole network in a surreptitious way like the NSA is doing by tapping all SWIFT traffic. Therefore, the definition of "law enforcement" is not a magic attribute or key stored by the network, rather it's implicit: the party who can convince nodes to collaborate to deanonymize other nodes.
Additionally, it would be desirable to prevent anonymous laundry services while keeping the network open to join like Bitcoin, without the classic KYC routine of banks. This seems like a contradiction (Sybil attack) but maybe some compromise exists, so your thoughts are much appreciated.