What are Schnorr signatures?

Schnorr signatures is a lightweight signature scheme that seeks to improve the privacy of Bitcoin and other cryptocurrencies. It will also allow the application of new technology in order to improve the capabilities and scalability of the blockchain.

Las Schnorr Signatures or Schnorr firms, is a solution proposed on the network Bitcoin what are you looking for improve privacy and scalability of the system. By allowing a set of transaction signatures with the same entry to be replaced by a single signature. Reducing the storage space occupied within a block. This, in turn, allows transactions to be confirmed much faster, improving network performance. The improvement proposal was presented by Pieter Wuille in July 2019.

This new signature scheme also allows to improve network security, against spammer attacks. Since with this implementation, an attacker would have to send much more transactions to occupy the same space within a block. Making the attack more expensive and less feasible for the attacker.

How do Schnorr signatures work?

The main function of Schnorr signatures is to allow multiple users to create a single signature for all parties involved. Reducing the size of transactions and the number of signatures necessary to carry out a transaction.

The Bitcoin system uses the algorithm ECDSA Elliptic curve digital signature, so that users can demonstrate their ownership of bitcoins unspent outputs (UTXO). So, every time a user wants to carry out a transaction, they must provide a signature that validates their property. In turn, said transaction also have a script P2SH, which will determine how the entries of a transaction will be spent.

These scripts can be modified to condition or schedule the spending of the bitcoins. For example, you can set conditions for time lock o multisig. In the latter, multiple signature settings are required to authorize a transaction. Multisig employ an M-of-N scheme, where any combination of valid signatures within N can unlock unspent outputs, by requesting a threshold with M number of valid signatures. So, to authorize a transaction and spend an exit, M number of signatures must be provided between the participants; where each of these signatures has a size in bytes of length.

In other words, suppose that María, Juan and Pedro have a multisig wallet, where, to carry out a transaction, 2 of the 3 participants must sign. In this example, any combination of signatures (N) will be able to authorize the transaction, whether Maria signs with Juan, or María with Pedro, or Pedro with Juan. Or in your case, there is another condition that determines who should be the main signatories. But in general, the fulfillment of 2 firms (M) will authorize the transaction. However, the byte size of a multi-sig transaction will be larger than a conventional transaction that only requires a signature.

This is where the problem lies. As multi-sig by having to provide a certain number of signatures to authorize a transaction, the size of the transaction will grow proportionally to the number of signatures that are required. So the implementation of Schnorr signatures represents a real solution to this problem. This solution combines all the individual firms within the same firm, reducing, in turn, the size of the transactions and the costs generated by the transaction fees.

Advantages and disadvantages of Schnorr firms

Pros

1. Implementation of this signature scheme can improve network privacy, by allowing Schnorr signature transactions to look identical to conventional single-signature transactions. So they are indistinguishable from each other.
2. Schnorr firms reduce the need for storage space for transactions with multi-signatures, up to 25%. So they decrease the size of the transaction within the block, saving your space and reducing commissions for such transactions.
3. By reducing the storage space of transactions within the block, Schnorr signatures can contribute to better network scalability.
4. This implementation It will allow transactions to be validated and confirmed much faster. In this way, the waiting time for confirmations on the network is significantly reduced.
5. Schnorr firms no malleability problemsTherefore, no party can modify or alter a signature to generate double expense.
6. They are an essential part for the application of tap root one of Bitcoin's most anticipated enhancements to enhance its scalability, privacy, and ability to smart contracts.

Cons

1. In the implementation of Schnorr signatures each participant must demonstrate that their public key It is valid, through a signature produced with its corresponding private key.
2. The implementation of Schnorr signatures exposes an attack vector where a participant can claim a false public key and control multi-sig.

MuSig Multiple Signature Scheme

The Schnorr signature scheme was created in 1980, by the German cryptographer Claus-Peter Schnorr. Who patented his invention, preventing the public and direct use of this scheme. In 2008, the panther of this creation expired, making it freely usable.

Subsequently, in 2018, several developers and programmers designed a new multiple signature scheme called MuSig, which is based on Schnorr signatures. This new scheme allows participants of a multi-sig, the creation of smart contracts private outside the blockchain.

In addition, with the implementation of MuSig, you can add the signatures and public keys of each participant of the multi-sig, and generate a single public key that verifies the others. Rather than having to verify each individual public key separately.

Schnorr and Bitcoin Cash firms

Taking advantage of the enormous similarity that exists between Bitcoin and Bitcoin Cash, the developers of Bitcoin Cash have decided apply Schnorr signatures to the variation of its protocol. It was developer Mark Lundeberg who carried out all this work to make Bitcoin Cash take advantage of this new signing scheme, which would be optional to the ECDSA system.

The Bitcoin Cash network was updated to make use of this type of signature on May 15, 2019. As a result of this update, Bitcoin Cash managed to reduce the size of the digital signatures of the transactions by 4%. And at the same time, reduce the size of transactions by 20% with the consequent increase in the network's processing capacity.