Schnorr signatures (s.v. "Schnorr"): Schnorr, named after its inventor Claus-Peter Schnorr, is a signature scheme: the series of mathematical rules that link the private key, public key and signature together. Many cryptographers consider Schnorr signatures the best in the field, as they offer a strong level of correctness, do not suffer from malleability, are relatively fast to verify, and ‒ importantly ‒ support multisignature: several signatures can be aggregated into a single, new signature. · However, until now it has not been possible to utilize Schnorr in Bitcoin. Another type of signature scheme, Elliptic Curve Digital Signature Algorithm (ECDSA), is baked into the Bitcoin protocol, and changing that would require a hard fork. (†2038)
segregated witness (s.v. "Schnorr"): With Segregated Witness, all signature data is moved to a separate part of the transaction: the witness, which is not embedded in the “old” Bitcoin protocol. And thanks to script versioning, almost any rule applied in the witness can be changed through a soft fork. Including the type of signature scheme used. This opens the door for Schnorr. (†2039)
