Learning objectives

After this chapter, you should be able to:

• Separate transaction validity, transaction ordering, finality and service availability.

• Explain the roles of hashes, signatures, full nodes, miners and validators.

• Explain why Shor's algorithm threatens digital signatures differently from quantum search against hashes.

• Identify public-key exposure, post-quantum protections and the steps required to migrate existing assets.

• Assess quantum urgency through technical evidence and migration lead times rather than a fixed predicted attack date.

• Compare proof of work and proof of stake through their security assumptions and failure modes.

• Distinguish a temporary reorganisation from a protocol upgrade or a durable chain split.

• Explain why correct smart-contract execution can still produce an economically wrong result.

• Evaluate scaling proposals across execution, data availability, settlement and recovery.

• Identify the additional dependencies introduced by sequencers, bridges and administrative powers.

• Translate a network architecture into funding requirements, monitoring responsibilities and credible recovery procedures.