Recall our earlier assumptions about Bitcoin: we can’t trust anyone.
Before, we considered trust in the context of consensus, but what about information that moves through the network? For example, if someone sees a block with my transaction in it, what’s to stop them from modifying or even replacing it? We previously demonstrated how to have consensus on updates to the blockchain through Proof-of-Work.
Now, we will demonstrate how we can be certain that the update is the same for everyone by designing a tamper evident system.
Tamper evident means that although information can be tampered, it is obvious that there has been some manipulation of the information.
We’ll see that in order to design our tamper evident database, we first need a source of standardized randomness.
For this, we’ll utilize cryptographic hash functions.