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DHS Looking Into Tracking Monero and Zcash Transactions (zdnet.com)
The US Department of Homeland Security (DHS) is interested in acquiring technology solutions that can track newer cryptocurrencies, such as Zcash and Monero. From a report: According to a pre-solicitation document [PDF], the DHS wants to know if this is possible, before filing an official solicitation request later down the line. The DHS said that "prior efforts have addressed Bitcoin analytics," but now the agency and the law enforcement agencies under its supervision are looking into similar cryptocurrency analytics solutions that can be used to track so-called privacy coins -- cryptocurrencies that support anonymous transactions.
"A key feature underlying these newer blockchain platforms that is frequently emphasized is the capability for anonymity and privacy protection," the DHS document said. "While these features are desirable, there is similarly a compelling interest in tracing and understanding transactions and actions on the blockchain of an illegal nature. This proposal calls for solutions that enable law enforcement investigations to perform forensic analysis on blockchain transactions," it added.
"A key feature underlying these newer blockchain platforms that is frequently emphasized is the capability for anonymity and privacy protection," the DHS document said. "While these features are desirable, there is similarly a compelling interest in tracing and understanding transactions and actions on the blockchain of an illegal nature. This proposal calls for solutions that enable law enforcement investigations to perform forensic analysis on blockchain transactions," it added.
NSA has been doing the OAKSTAR "math" to track senders and receivers of digital currency for years.
"The NSA Worked To “Track Down” Bitcoin Users, Snowden Documents Reveal" (March 21 2018)
https://theintercept.com/2018/...
A nice collect it all MONKEYROCKET project with timestamps, MAC address, network ports, internet addresses.
Domestic spying is now "Benign Information Gathering"
I'm not saying the currencies are safe against active attackers, or people wishing to just mess with the block chain, this is just about privacy and scanning the block chain.
Assuming we can create a secure hash function and people use truly random numbers then the ring signatures used in Monero are secure in that they reveal no knowledge about who signed the message. Anyone of the private keys associated with the public keys could have been the signer. Your next option would be to try and track transaction inputs and outputs but even these permit any possible value. So just looking at the block chain, even if you have a quantum computer and can solve the discrete log problem (DLP), you aren't going to learn much. As an active attacker, one who is creating outputs that they hope their intended victim will then use as inputs, and again possessing a way to solve DLP, maybe but you will have to solve one DLP for every attack. There might be a way to double spend many times if you could solve the DLP once. That's because you could solve a relation between two generators of the elliptic curve group used by RCTTypeFull, but that exploit will likely be closed before anyone develops a working quantum computer large enough to attack Ed25519.
Further reading:
https://www.getmonero.org/libr...
Zcash uses a different group membership algorithm. It could be broken if you had a quantum computer, but again you have to solve either the DLP or RSA problem for each transaction you wish to investigate. It will be years before that computing power is feasible to spend on one transaction.
There are no good resources, that I would recommend, for Zcash and other zero coin derivatives.