Transactions make changes to storage and have fixed transaction costs. Transactions are executed on every node. Transactions can only return results by events. One Contract Transact On Another and get returned data. TRANSACTION FAILURE ALL CHANGES REVERSED, NO LOG PRODUCED
Transactions can POST a Contract Another transaction can call that contract.
Hashing is the product of a small change in content which causes a huge change in results.
Public Key Encryption is the method to encrypt hash values.