PISA Demo Uses One Signature to Cut 16 vB From Bitcoin Transaction

A prototype called PISA combines Payjoin and cross-input signature aggregation in a two-input Bitcoin (BTC) transaction, cutting 16 virtual bytes (vB) by using one 64-byte aggregate signature for both inputs. Fabian Jahr announced the demo Oct. 23, describing it as work built at Lugano’s Plan ₿ event with support from Cypher Tank. Payjoin Dev Kit and Brink collaborated on the project. The event was part of the Plan ₿ Forum, scheduled in Lugano for Oct. 23-24. Payjoin lets a sender and receiver contribute inputs to the same transaction.