Ring Signature

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21 Aug, 2024

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Ring signature in cryptography refers to the type of digital signature utilized by the users from a group to sign a transaction. Here, a group of users form a ring to approve transactions. Its sole purpose is to sign a transaction anonymously without actually revealing the identity of the users.

The origin of the ring signatures dates back to the early 21st century. A group of cryptographers, namely Ron Rivest, Yael Tauman Kalia, and Adi Shamir, introduced this concept in 2001. These are often used in privacy-focused cryptocurrencies like ring signature Monero. Likewise, in 2006, professors Eiichiro Fujisaki and Koutarou Suzuki also proposed traceable ring signatures.

What Is Ring Signature?

Ring signatures refer to the anonymous way of signing the transaction without revealing the real identity of the user in a group.
It originated after the White House leak dilemma that occurred in the 21st century. Thus, cryptographers Ron Rivest, Yael Tauman Kalia, and Adi Shamir proposed this concept in 2001.
There are three types of signatures in rings, namely linkable, traceable, and threshold. While sending data or funds, an extra signature gets added for tricking hackers.
Some of the blockchain implementing them include Monero, Bitcoin, and Ethereum. Also, it is useful in whistleblowing, messaging protocols, and voting systems.

Ring Signature Explained

A ring signature is a cryptographic technique that allows a user to sign a message on behalf of a group. It allows anyone from a group of crypto users to sign the transaction without revealing their identity. In short, they form a ring structure for transaction signing. Thus, any user can quickly sign in with the help of the allotted private and public keys. Likewise, a significant transaction involving crypto tokens can be safely sealed with the ring signature algorithm. It was first used during the White House leak dilemma case to avoid any future data leaks.

There are three major types of these signatures, namely threshold, traceable, and linkable. While the former allows collaboration of specific users for a transaction, the traceable ring signatures can reveal identity quickly. In short, if a user signs two messages at the same time, it is traceable. Likewise, linkable signatures allow detection in case of dual signatures by a single user.

Hence, the mechanism of the ring signatures involves a group of users who own public and private keys. So, when a transaction occurs, it gets hashed into a message. Later, this message reaches a ring of crypto users. This ring consists of different public vital owners. However, before this, the sender has to create a signature with its private key and attach it to any public key. Eventually, the assigned member signs the message and completes the transaction.

Once all the signatures get signed, they are clubbed together to complete the transaction. As a result, if any intruder tries to detect the original sender, they may fail. Even though signatures can match with any public key, they need help to guess the correct one. Thus, these signatures contribute to the privacy and fungibility aspects of cryptocurrencies.

Examples

Let us look at some examples of ring signatures to comprehend the concept easily:

Example #1

Suppose Kevin is a market trader who deals majorly in cryptocurrencies. He has been dealing with them for more than four years. However, the only issue he faced was privacy. Whenever Kevin tried to stay consistent with any platform, there was always a threat of cyber-attacks. Therefore, he decided to deploy ring signatures in his transactions. As a result, he switched to the Monero network. Here, Kevin had an option to hide his real identity while using these signatures. After a few days, he tried the platform to make a transaction.

Kevin wanted to send 20 BTC to Jessy via blockchain mode. So, he initiated the transaction and opted for these signatures. Later, the blockchain collected a random list of public keys from past transactions and presented them to Kevin. As a result, he could make a ring of certain public keys. Once selected, the sender created a signature with his private key and sent it to Jessy. At the same time, one more signature of User B and C's public key was added.

In the end, blockchain combined all to form one signature. Thus, it made it impossible for malicious actors to guess the original parties (Kevin and Jessy).

Example #2

Imagine a group of individuals who each possess a public-private key pair in a privacy-focused cryptocurrency network. Now, let's say Alice wants to send a transaction without revealing her identity. To achieve this, she creates a ring signature. She selects a group of public keys, including her own and those of other users, forming a "ring" of potential signers.

When Alice signs the transaction, the ring signature algorithm combines her private key with the other public keys in the ring to create a signature. This signature is valid for the entire group, but it doesn't disclose which specific private key (user) was used. Subsequently, anyone verifying the signature can confirm its validity without pinpointing the exact individual who signed the transaction. In this way, ring signatures provide a layer of anonymity within the group, contributing to the privacy features of the cryptocurrency.

Applications

With the popularity of linkable ring signatures, its significance has also grown in some platforms. Let us look at their applications:

#1 - Cryptocurrencies

One of the significant implications of these signatures is visible in the blockchain networks. It helps to trick the cyber attackers about the transaction. The users can hide their identities with these signatures while dealing with other users. As a result, anonymity prevents thefts of crypto funds stored in wallets. For example, Bitcoin, Ethereum, and Monero are the popular blockchains with this feature.

#2 - Whistleblowing

The primary reason for the existence of linkable ring signatures is the famous White House case. At that time, some secret data of the federal government got leaked anonymously. As a result, the cryptographers proposed this technique for whistleblowing. Major organizations and firms can implement this mode, where certain malpractices or unethical behavior can be disposed of easily without any identity reveal.

#3 - Voting Ballots

In addition, governments can decide on the ring signatures in the voting systems. For instance, the list of voters can form a ring (or group), and their respective votes would be combined in the end. As a result, it may be tricky to track voter's identity. Furthermore, equivalent anonymity and privacy of the process are maintained.

#4 - Messaging Protocols

Also, social media applications can deploy these signatures in the messaging systems. For example, firms can create such rings to get effective feedback reviews from the employees.

Advantages And Disadvantages

Following are the advantages and disadvantages of ring signatures in cryptography. Let us look at them:

Advantages	Disadvantages
It maintains enough anonymity within a transaction.	Deploying these signatures can increase network load and transaction fees, too.
They increase privacy and security on the blockchain network.	The anonymity of the transaction still needs to be fully guaranteed if the details of the original parties are known.
These signatures make it difficult for hackers to trace crypto transactions.	Ring signatures tend to be larger than traditional signatures, as they include the public keys of multiple participants.
Users within the ring can deny being the actual signer since the signature is valid for the entire group.	Managing the keys within a ring can be challenging, especially in scenarios where membership changes frequently.

Frequently Asked Questions (FAQs)

1. Are ring signatures more secure than zk-snarks?

In a better comparison between both, ring signatures are older than zk-snarks. As a result, the latter is more secure when deployed. However, zk-snarks do demand a complex setup and computational load. In contrast, rings are easy to implement.

2. Who uses ring signatures in cryptography?

Mainly, software developers use ring signatures to create security layers around the protocol. It is used in the ring confidential transactions (CTs) to adhere to the privacy concept. For instance, the CryptoNote protocol hides the actual addresses of the wallets involved.

3. How many ring signatures are required in a Monero transaction?

Usually, one signature is enough to sign the transaction. In short, a single sign can easily transmit the ring signature message even if others act as decoy versions.

4. What is the ring size on the Monero network?

In cryptography, the ring size decides the number of users in a ring. On the Monero network, the size is 11. However, before the release of the 0.13 version, the ring size of signatures was 16.