Earlier this month, the Monero team announced the release of a new solution to better protect data on the cryptocurrency network. In this article, we'll take a look at Triptych, an innovative Monero technology that hides coin sender data by increasing the number of traps.
Ring signatures
Address protection alone is not enough to hide sender information on the Monero network. All Monero transaction data is represented on the blockchain as outputs (TXO). In turn, each TXO is marked with a unique (one-time) identifier or public key. So, when monitoring the Monero blockchain, the ability to bind TXO public keys to user addresses is not possible. However, the public keys themselves need protection, given that there are various blockchain tracking methods that can associate these public keys with people.
The movement of Monero across the network is classified using the ring signature method. With this approach, hiding the public key for the actual TXO occurs by including traps in the transaction in the form of inputs / outputs of other people's transactions. Thus, it is impossible to determine the authenticity of the TXO. In turn, TXO inputs and outputs can be monitored directly in Monero blockchain explorators such as moneroblocks.info or xmrchain.net.
Note that the ring signature method has been subject to transformation over the years. Traps were originally optional and were randomly selected. However, over time they became an integral part of the protocol, and their number was increased to 10. The sampling process has also improved over time, providing a case-by-case process.
The basic ring signature algorithms were also subject to improvement. The CryptoNote whitepaper describes a ring signature scheme that differs from the current more efficient implementation based on Multilayered Linkable Spontaneous Anonymous Group Signature (hereinafter referred to as MLSAG). One of the most recent innovations is the replacement of MLSAG with the CLSAG scheme, which is intended to reduce the overall size and time of transaction verification.
These efforts have only increased the anonymity of the Monero network. So, each XMR transfer with a real TXO in the form of a TXO public key is already cryptographically disconnected from the sender's Monero address and hidden among 10 false public keys that are difficult to distinguish from real ones. At the same time, the cryptocurrency software works quickly and smoothly, maintaining the standard speed and without affecting the size of the blockchain as a whole.
Challenges
But Monero's sender hiding mechanism is not perfect, and ten traps are not always enough. For example, some random TXOs can be identified through existing blacklists or linking to pools and exchanges, assessing the credibility of other transactions, and using time frames. And this is the problem.
Thus, you can hide among traps only when no one knows about them, and for some opponents, especially inventive ones, just 10 random choices may be enough to identify the parties to the transaction. So why not use more?
Note that the MLSAG / CLSAG algorithm implies an increase in the size of a transaction along with its processing time in relation to the number of traps in a linear progression. Thus, using 10 traps is the best option for maintaining an appropriate level of confidentiality at a normal processing speed and transaction size. More traps will undoubtedly increase privacy, but also increase the size of transactions, making them much more difficult to verify.
Triptych
As a solution to this problem, Monero developers Saran Noezer and Brandon Goodell partnered with Arthur Blue (RandomRun) to create an algorithm for Triptych ring signatures. In this case, the size of ring signatures grows not linearly, but logarithmically, like the mechanism working in the Zcash cryptocurrency. Thus, the verification time grows in a linear progression with the number of traps, but the verification can be performed using specialized algorithms that provide faster processing.
Triptych solves a number of issues regarding ring signature application to Monero. So, this method should block the reuse of public keys, thus preventing the possibility of re-spending the same TXO. The technology also supports the use of confidential transactions to hide amounts on the network. Thanks to special data called commitment keys, network participants prove the authenticity of the amounts being held, without the need to disclose them. These commitment keys, along with the signing keys and binding tags, represent the three main components of Triptych.
However, the project team is not going to stop there. One alternative, Arcturus - a particularly promising one - is an enhanced version of Triptych itself. The update will reduce the size of the transaction by using one cryptographic signature data packet for the entire transaction instead of
