Btrust Builders on Nostr: This week we wrapped up Week 4 of the live cohort, continuing our deep dive into how ...

This week we wrapped up Week 4 of the live cohort, continuing our deep dive into how Bitcoin enforces rules and verifies transactions.

Over the past week, participants studied chapters 7 and 8 of Mastering Bitcoin, met with their learning partners to discuss the material, and then came together for the group session.

The week began with a closer look at authorization and authentication in Bitcoin. Instead of relying on identities, Bitcoin uses scripts to define the conditions for spending funds. The group explored how these scripts are evaluated, and how transactions are only valid when those conditions are satisfied.

From there, the conversation moved into Bitcoin Script itself. Participants looked at how the stack-based language works, how input and output scripts are combined during validation, and how different script types like P2PKH, multisig, and P2SH are used in practice. The group also discussed timelocks and how they can restrict when funds are spendable.

After building a foundation with scripts, the cohort shifted into digital signatures. Participants learned how signatures prove ownership of funds, authorize transactions, and protect transaction data from being altered. The group walked through how signatures are created and verified using private and public keys.

The discussions also covered the differences between ECDSA and Schnorr signatures, and why Schnorr offers improvements in simplicity, efficiency, and privacy. Participants explored how signatures can commit to different parts of a transaction using SIGHASH flags, enabling more flexible transaction designs.

A key focus was the importance of randomness in signing. The group reflected on how reusing a nonce can expose a private key, reinforcing how small implementation details can have serious consequences.

By the end of the session, participants had a clearer picture of how Bitcoin enforces spending conditions and verifies transactions without relying on trust. The discussions helped connect scripting and signatures into one coherent system that underpins how Bitcoin works.