Reducing Bitcoin Transaction Sizes with x-only Pubkeys

How to securely save four weight units per output with BIP-schnorr

Introduction

Background

compressed public keys

What is the purpose of the tie breaker?

Purpose of tie breaker
x-only pubkeys in BIP-schnorr
Why can we remove the tie breaker?

Why introduce x-only pubkeys?

Why x-only?

Proof sketch

Proof sketch model of the forger
Proof sketch outline
Proof sketch case 1
Proof sketch case 2
Proof sketch resolution

Conclusion

BIP-schnorr and BIP-taproot are slowly maturing from the draft status to the proposal status. We’re looking for feedback, so feel free to read the BIPs, implement them, or play with implementations of BIP-schnorr and BIP-taproot. Very good resources for learning more about the BIPs are this Jupyter notebook from the Optech Taproot workshop and the Taproot Review Club.

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