How are Bitcoin transactions secured?

Bitcoin transactions are secured primarily through cryptographic signatures and immutability, which are fundamental components of the Bitcoin protocol. Each transaction is digitally signed by the sender using their private key, creating a unique cryptographic signature. This signature verifies that the sender is indeed the owner of the Bitcoin being sent and prevents anyone from altering the transaction without invalidating the signature.

Furthermore, immutability refers to the feature of the blockchain that ensures once a transaction is recorded, it cannot be changed or deleted. This is achieved through a consensus mechanism and the chaining of blocks, where each block contains a hash of the previous block. Altering any transaction would require re-mining all subsequent blocks, which is computationally infeasible.

This combination of cryptographic signatures and the immutable nature of the blockchain provides a robust security structure for Bitcoin transactions, ensuring both authenticity and integrity.