Monero (XMR) is a ledger project that has gained worldwide acclaim as a leader among privacy-centric cryptocurrencies.
Monero's differentiation has enabled the project to identify a special niche in the blockchain community because of its accentuation on matters concerning private e-monies.
Like Bitcoin, Monero employs the UTXO framework even though the Monero structure is highly dynamic.
Thus, the design changes in the aspects of UTXO packaging and broadcast.
The Monero protocol uses a one-time ring signature construction, which on-lookers, third-party players, are barred from identifying the output of.
Additionally, Monero utilizes stealth addresses that apply one-time public keys to contribute to overall crypto privacy.
Before getting carried away with the nitty-gritties of blockchain-associated technologies, we have to agree that ring signatures have become a sure bet for the integrity of Monero values.
This virtue, among others, has been identified as a key strength of the Monero project, which happens to override some merits of Bitcoin use.
In candid terms, Monero's strong fungibility has enabled the virtual coin to stand out from its peers.
The Broad Perspective: Ring signatures, RingCT and Stealth Addresses
In order to fully comprehend the substance of ring signatures in Monero, vis-à-vis other forms of digital signatures, it is prudent to illuminate the big picture of the whole cryptographic process.
We'll take a brief look into the three chief tools that obscure information on Monero's blockchain.
In simple terms, ring signatures, RingCT and stealth addresses serve individual interests of the sender, receiver, and amount, respectively.
An Analogy
Consider the real life scenario of money transactions in our daily lives.
If you intend to settle a debt with your friend of, say, $100, you simply issue them a $100 bill. This sounds quite straightforward.
In context of the Monero network, the same scenario holds truth, except that the dollar bill becomes replaced with a loaded output.
Now, the output becomes available to the recipient to spend as they like.
Ring Signature
To uphold a sender's privacy, Monero creates a "deceptive" scenario that will indicate that several outputs were involved in sending an amount the receiver.
This happens even though only one output was actually used.
RingCT
Ring confidential transactions hide information about the amounts being transacted. In other words, the values of outputs become anonymized.
Stealth addresses
With stealth addresses, the analogy of "one-time safety deposit boxes" is applied.
This is a contrast to the Bitcoin network in which monies are sent directly to recipient addresses.
In the end, the receiver becomes the only individual that can "open the box" to unravel its contents.
Fundamental Details of Ring Signatures
Ring signatures share a plethora of similarities with group signatures.
The dissimilarity presents itself with the particular workings of the tool.
Ring signatures have been identified as an improvement of group signatures within the echelons of user privacy.
Cryptocurrencies like Monero apply the typical P2P transaction format, and ring signatures serve to obscure the input end of processes.
This function protects the sender by making it practically impossible for anyone to identify the actual signer of a transaction.
Ring Signatures in Monero
As mentioned above, ring signatures work to enhance the privacy of transactions.
The ring signature in Monero constitutes a signer who is connected with non-signers to establish a ring. By now, the origin of the term "ring" should be pretty self-explanatory.
Otherwise, before diving in, it is prudent to understand that the actual signer and their non-signer counterparts are handled as a unit - they are all equal.
Actual signers denote one-time spend keys that reflect the actual output emanating from the sender's wallet.
Non-signers, on the other hand, refer to past transaction outputs that are sourced from the Monero blockchain.
These past outputs serve as decoys in the ring signature process, which play the important role of being a constituent of transactional inputs.
From an outsider's view, the entirety of the input elements is perceived as the likely output being dispensed in a transaction.
What's the Point?
Monero uses this technology to enable the sender to cloak the source of a transaction by obscuring the input attributes that may allow an observer to distinguish one input from the other.
By this, all inputs become indistinguishable from one another.
Key Image
Monero's application of the ring structure technology translates to the need to include a tool for verifying outputs.
This aspect is critical because users can spend transaction outputs twice - called double-spending. Monero counters this possibility through the application of a key image.
By definition, key images denote cryptographically-secure keys that emanate from the process of output spending.
This feature is utilized in each and every ring signature transaction.
The working principle of the key image is built on exclusivity - only one key image is assigned to each transaction that occurs on the Monero blockchain.
The inherent nature of key images guarantees the impossibility of discovering the output sources of the key image.
Case Example
Now that we have dwelt on the theoretical aspects of the ring signature technology, this section seeks to purify the principles covered so far.
Hence, the basic workings of Monero, in the ring signature context, is elucidated by the following hypothetical example:
- Emily intends to send Jack five Monero - she will launch a transaction via her Monero wallet to Jack.
- Emily's digital signature, in this context, will be a one-time spend key that begins with an output originating from her wallet.
- The non-signers of the ring signature will be transaction outputs associated with past processes, which will be selected from the Monero blockchain and serve as decoys in the transaction.
- All ring constituents are credible signers, for this case, and it becomes technically impossible for a third party to identify the actual signer.
- Thus, outputs of the ring signature, in totality, constitute the transaction's input.
- Emily, the initiator of the transaction, is qualified to spend the prescribed transaction amount without isolating her identification from her peers in the ring structure.
- Most notably, even though Emily's public key is imperative to her own transaction, it may be applied in other processes on the Monero platform as a disorganization agent.
Wrap Up
While glossing over the shortcomings of the Monero protocol, the ring signature technology is, equivocally, one of the network's strongest points.
It gives Monero an edge over its crypto counterparts like Bitcoin.
Stealth addresses, as an example, only obscure the destination of a transaction while ring structures hide transactional sources.
Agreeably, ring structures become vital in that they eliminate proofs of outputs ever being spent in the first place, making Monero one of the most privacy- and anonymity-centric cryptocurrencies on the market.