PPT Slide
(Making sure no one tampers with data in route from one place to another)
Hash functions take a large file and reduce them to a short number between 128 and 512 bits which can be used as a surrogate for a long digital signature file. Two important properties are (a) all possible short number are equally likely to emerge from the hash function, and (b) it should be impossible o recreate a file that generates any particular pair. If I send you a file, the we could both compare the hash function of our files, if they match, the files haven’t been tapered with.
- Double Blinded Signatures:
(Permitting Anonymous Digital Cash Transactions)
Would you sign a Bank Check?
Some digital systems require banks to digitally sign something with out knowing it’s contents. This scheme is used in anonymous digital cash where the bank is prevented from keeping track of the serial numbers of digital bills.
(Preventing Double Spending of Digital Cash)
This system splits data up into ‘n’ parts, and required all ‘n’ parts to be available to reconstruct the information. It is used in digital cash transactions to prevent double spending. If someone spends a digital bill twice, then there is enough information available to reconstruct the spender’s identity.