TU Wien:Smart Contracts VU (di Angelo)/Prüfung 2021-06-17

Multiple blocks of MC-questions, each block having 3 points. Within a block, a wrong answer gives negative points, however, a block in total cannot lead to less than 0 points.

1. A collision-resistant hash function
   1. has only a few collisions.
   2. doesn't have any collisions.
   3. has collisions, but they are infeasible (practically impossible) to find.
2. When using a commitment scheme com = commit(data, nonce),
   1. the data has to be submitted at the same time as the commitment com.
   2. the nonce has to be submitted at the same time as the commitment com.
   3. the data and the nonce have to be provided for verification.
3. For a commitment scheme, a hash function is required to have the property of
   1. hiding
   2. binding
   3. committing
4. In a digital signature scheme with sig = sign(sk, message), the signature sig changes when
   1. the private/secret key sk is leaked.
   2. the message changes.
   3. the time stamp of the signature sig changes.
5. A hash pointer allows us to
   1. check the integrity of the data to which it points.
   2. prevent changes to the data to which it points.
   3. access the data to which it points.
6. A hash pointer is
   1. a pointer to the hash of the data.
   2. the hash value of the previous hash.
   3. a pointer to data together with a hash value of the data.
7. To verify a signed message in a digital signature scheme, a receiver needs (among other things)
   1. the sent message.
   2. the private key of the sender.
   3. the signature for the message.
8. The checks-effects-interactions pattern means:
   1. Immediately after all checks passed, changes to the state of the current contract should be made.kiw
   2. Only after changes to the state have been made, the effects can be checked and interactions can be made.
   3. Only when an external function call returns no error, it is safe to change the state of the current contract.
9. In Ethereum, the ordering of transactions can be
   1. determined by the winning miner.
   2. influenced by setting a higher gasprice.
   3. relied upon by a smart contract.
10. In Ethereum programming, you should be aware that
    1. private data in smart contracts is visible to anyone.
    2. public functions may be called maliciously and in any order.
    3. only the owner can initiate a selfdestruct.