[Cryptocurrency] Shadowcash Hits Zero-Knowledge Jackpot with Casino-style Anonymity - DeepDotWeb
[5 Points] sexystick:
[5 Points] throwaway10010034:
Just leaving this here:
You'll find that Monero had that long before them, and the CryptoNote reference code a month or so before that.
This is because you're misusing a cryptography term (zero knowledge) without understanding what it means. It is used to describe a special type of cryptographic proof: zero-knowledge proofs. What this means is that, for example, Peggy can (mathematically, cryptographically) prove to Victor that she knows the password to open a secret door without telling Victor the password. The story given in the 1990 paper by Jean-Jacques Quisquater involves "Victor" observing "Peggy" going into a path with the secret door, and then coming out via an exit of his choosing. If Peggy repeatedly appears at the correct exit then it is overwhelmingly probable she knows the secret word to open the interleading door. If she fails to appear correctly even once, then she clearly does not know the secret word.
Thus, zero-knowledge proofs must have the normal properties of interactive proof systems, that is completeness (an honest verifier is completely convinced by an honest prover, if the statement is true) and soundness (within an acceptably small probability, no fake prover can convince an honest verifier that a false statement is true). The downside to these systems is that a fake verifier can learn the statement from an honest prover. The special property of interactive zero-knowledge proof systems is that a fake verifier only learns whether the statement is true or false, not what the statement is.
Thus, even Bitcoin has a form of "zero-knowledge proof", did you know that? When you sign a transaction and broadcast it, nodes are able to verify that your transaction is valid even though they don't know your private key. All public/private key cryptography is verifiable via a form of zero-knowledge proofs:)
Specifically in the context of cryptocurrencies, though, the original CryptoNote protocol, as well as Monero's push beyond that, has lead to a blockchain that is fully cryptographically verifiable, but it is impossible to know the value of a transaction or even who the recipient is. This is primarily due to a single special component: key images. Because key images are always unique, they prevent outputs from being double-spent (and thus breaking the cryptographically sound verification). Unsurprisingly, you'll find that ShadowCash reimplemented the key image functionality (which only exists courtesy of CryptoNote and, by extension, Monero), which is why they are able to claim that they have zero-knowledge proofs.
Don't believe me? Here is their function to generate key images: https://github.com/SDCDev/shadowcoin/blob/master/src/ringsig.cpp#L165
I really do recommend you spend some time researching and understanding the cryptography involved before making any further statements on this subject.
[2 Points] None:
tl;dr ?
[0 Points] TheLobstrosity:
This article put things in perspective quite nicely.
As a Shadowcash holder and fairly active community member, it seemed as though many folks weren't quite grasping the white paper.
ELI5:
Bob has old, smelly, dirty $100 bill (100 ShadowCash SDC)
Bob goes to casino and trades $100 bill for $100 worth of chips (100 SDC -> 100 Shadow in denominations of 1,3,4 & 5)
Bob trades $100 worth of chips (100 Shadow) back to casino
Casino gives Bob new, clean, rosey $100 bill (100 SDC)
Caveat: With ShadowCash, Bob is the Casino. He only needs to trust himself, not a 3rd party