All things comes to an end. his includes the universe itself. Even if we take a look at the small speck of time we are living, the networks and services we use are not exactly unhackable. There is always a way and the only real security we can have is making things next to impossible. The reason Bitcoin is secure is because no computer can brute force through the cryptography without burning a great deal of resources that can not justify the cost. Our privacy tech is also facing similar conditions.

An Empirical Analysis of Traceability in the Monero Blockchain

[Malte Möser, Kyle Soska, Ethan Heilman, Kevin Lee, Henry Heffan, Shashvat Srivastava, Kyle Hogan, Jason Hennessey, Andrew Miller, Arvind Narayanan, Nicolas Christin]

last revised 23 Apr 2018

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This is a 22 page analysis on XMR which is hailed as the best privacy coin by many cypherpunks and Dark Net enthusiasts. Some of my own thoughts can be found here. Lots of fanatics may convince you that it is the holy grail of privacy and that it is without flaws. But the reality is different. It's good to know things and attempt to improve them rather than defending a flawed system that sacrifice performance for privacy.

Abstract:

Monero is a privacy-centric cryptocurrency that allows users to obscure their transactions by including chaff coins, called "mixins," along with the actual coins they spend. In this paper, we empirically evaluate two weaknesses in Monero's mixin sampling strategy. First, about 62% of transaction inputs with one or more mixins are vulnerable to "chain-reaction" analysis -- that is, the real input can be deduced by elimination. Second, Monero mixins are sampled in such a way that they can be easily distinguished from the real coins by their age distribution; in short, the real input is usually the "newest" input. We estimate that this heuristic can be used to guess the real input with 80% accuracy over all transactions with 1 or more mixins. Next, we turn to the Monero ecosystem and study the importance of mining pools and the former anonymous marketplace AlphaBay on the transaction volume. We find that after removing mining pool activity, there remains a large amount of potentially privacy-sensitive transactions that are affected by these weaknesses. We propose and evaluate two countermeasures that can improve the privacy of future transactions.

On the linkability of Zcash transactions

[Jeffrey Quesnelle
University of Michigan-Dearborn]

Submitted on 4 Dec 2017

Zcash has had some monumental achievements and when mos people point flaws of the system, at many times they can't go beyond pointing at the trusted setup. Zcash is a cryptocurrency that utilize zero knowledge proofs which is another way of saying proving that you know something without revealing what you know and I believe the dev team has massively contributed to the enhancement of the privacy of our technological civilization.

But achievements shouldn't blind us to potential problems and it is always safe o investigate and improve the available tech. It's good not to settle.

Abstract:

Zcash is a fork of Bitcoin with optional anonymity features. While transparent transactions are fully linkable, shielded transactions use zero-knowledge proofs to obscure the parties and amounts of the transactions. First, we observe various metrics regarding the usage of shielded addresses. Moreover, we show that most coins sent to shielded addresses are later sent back to transparent addresses. We then search for round-trip transactions, where the same, or nearly the same number of coins are sent from a transparent address, to a shielded address, and back again to a transparent address. We argue that such behavior exhibits high linkability, especially when they occur nearby temporally. Using this heuristic our analysis matched 31.5% of all coins sent to shielded addresses.

An Empirical Analysis of Anonymity in Zcash

[George Kappos, Haaroon Yousaf, Mary Maller, Sarah Meiklejohn]

Submitted on 8 May 2018

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This is a more recent research paper and these 15 pages could even work as bit on an introduction into the Zcash project. The content gets a little dense as you go on but it's a very noob friendly report. I'm not a programmer and I'm not a cryptographer. Yet it wasn't a hard read for me.

Abstract:

Among the now numerous alternative cryptocurrencies derived from Bitcoin, Zcash is often touted as the one with the strongest anonymity guarantees, due to its basis in well-regarded cryptographic research. In this paper, we examine the extent to which anonymity is achieved in the deployed version of Zcash. We investigate all facets of anonymity in Zcash's transactions, ranging from its transparent transactions to the interactions with and within its main privacy feature, a shielded pool that acts as the anonymity set for users wishing to spend coins privately. We conclude that while it is possible to use Zcash in a private way, it is also possible to shrink its anonymity set considerably by developing simple heuristics based on identifiable patterns of usage.

Suggestions for improvement:

Our heuristics would have been significantly less effective if the founders interacting with the pool behaved in a less regular fashion. In particular, by always withdrawing the same amount in the same time intervals, it became possible to distinguish founders withdrawing funds from other users. Given that the founders are both highly invested in the currency and knowledgeable about how to use it in a secure fashion, they are in the best place to ensure the anonymity set is large. Ultimately, the only way for Zcash to truly ensure the size of its anonymity set is to require all transactions to take place within the shielded pool, or otherwise signifi- cantly expand the usage of it. This may soon be computationally feasible given emerging advances in the underlying cryptographic techniques, or even if more mainstream wallet providers like Jaxx roll out support for z-addresses. More broadly, we view it as an interesting regulatory question whether or not mainstream exchanges would continue to transact with Zcash if it switched to supporting only z-addresses.

I'm Just The Messenger

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I didn't write any of these papers. I simply came across them. Personally I conclude Zcash to be much superior to XMR (especially with added volume and real world usage). But overall I still prefer Dash and PIVX over both of these projects due to their ability to brand, market and fund themselves in a decentralized manner bringing in more real world usage and therefore more volume.

I'm not responsible for the content of the research papers and you are free to conclude whatever you want after going through them. On going developments of the cryptosphere can make the content of these papers irrelevant in the future.