Schnorr Signatures Will Be Included In Bitcoin Cash’s May Upgrade to Enhance Privacy
In cryptography, a Schnorr signature is a digital signature produced by the Schnorr signature algorithm that was described by Claus Schnorr. It is a digital signature scheme known for its simplicity, among the first whose security is based on the intractability of certain discrete logarithm problems. It is efficient and generates short signatures.
Estimates are that this upgrade would reduce the use of storage and bandwidth by at least 25%. To point out the obvious: that is a huge efficiency gain. Another major benefit of Schnorr signatures is increased privacy as to how you are securing your bitcoins. Some users intentionally use multiple signatures to send transactions, as this is a way to increase security. You can require multiple people or devices to send a transaction for example, which is commonly known as MultiSig.
Schnorr signatures would also help combat spam attacks. If we only have one signature per transaction, more transactions will fit into blocks and a spammer would need to send far more transactions in competition with more people, and thus likely spend more money to take up the same transaction space. Signatures are often the largest individual part of a transaction, so the attacker would be disadvantaged. If the attacker chooses not to use Schnorr signatures and continues to use old signatures, then other users that do use Schnorr will still have smaller transactions to send and will thus have to pay less.
Bitcoin Cash developer Mark Lundeberg said on his Github:
“Schnorr signatures allow very simple multi-party aggregation schemes, where multiple parties collaborate to produce one aggregated signature under one aggregated pubkey, checked with OP_CHECKSIG as in pay-to-public-key-hash (P2PKH) addresses. Schnorr signatures cannot be malleated at all, even in the aggregated case, except when all signers collaborate to create a new signature from scratch.”
Even BTC developers have been discussing implementing Schnorr into the protocol, however, removing the ECDSA signatures and replacing them with a Schnorr scheme is a major upgrade. In almost all certainty, BCH will have a protocol in place before BTC.