Final Assessment

1. What language is the Bitcoin scripting language based on?

   • Fortran

   • Forth <-

   • Java

   • Function Block Diagram

2. What is the stack notation used in Bitcoin script called?

   • Inverse romanian notation

   • Push Before Opcode notation

   • Reverse Polish Notation <-

   • Satoshi Script Notation

3. True or False: Node operators have the right to change the opcode list at any time

   • True

   • False <-

4. When looking at a raw transaction, what do the last 4 bytes represent?

   • nVersion

   • nValue

   • nSequence

   • nLocktime <-

5. When nLocktime has a value less than 500,000,000, what is used to determine when the transaction can be mined?

   • This is a very early date in the Unix epoch so the transaction will be automatically final

   • Values less than 500,000,000 refer to a block-height instead of a time <-

   • It refers to the number of seconds that the transaction must wait in the mempool for

   • Such a transaction would be invalid

6. Under what conditions is a transaction valid and final?

   • The transaction's nLocktime is in the past but all its inputs are valid and have non-final nSequence values <-

   • Only one input is valid but all inputs are final and nLocktime is in the past

   • All inputs are valid and non-final and nLocktime is in 10 minutes

   • The only non-final input is invalid but the rest are final and nLocktime is in the past

7. Which of the following stack configurations will result in a valid input (final value is top of stack)?

   1. 0x01, 0x01, 0x01, 0x00

   2. 0x81

   3. 0x80

   4. 0x01

      • 1 and 3

      • 2 and 4 <-

      • 4

      • 2, 3 and 4

8. How many OP_ELSE statements can go into an IF loop?

   • 0

   • 1

   • Either of the above <-

   • There is no limit

9. What will OP_FALSE/OP_0 push onto the stack?

   • A null vector of zero length <-

   • A single byte containing 0x00

   • It depends if you use OP_FALSE or OP_0 - They are different!

   • It doesn't push anything to the stack

10. What does OP_NOP do?

    • It tells the evaluation engine to exit the script

    • It doesn't do anything <-

    • It checks if the top stack value is FALSE

    • It's a spare opcode and should not be used

11. What does OP_RETURN do?

    • OP_RETURN is just a type of output which carries data

    • OP_RETURN exits the script, with the top stack value determining whether it is valid or not <-

    • OP_RETURN exits an IF loop early

    • OP_RETURN returns the funds to the parent transaction

12. Which opcode copies the top stack item and places it behind the second from top stack item?

    • OP_2DUP

    • OP_ROT

    • OP_OVER

    • OP_TUCK <-

13. What does OP_SIZE do?

    • Returns the length of the stack

    • Returns the size of the transaction

    • Returns the size of the item on the top of the stack <-

    • Returns the value of the input being spent

14. Which of the following is a P2PKH script?

    • OP_DUP OP_SHA256 OP_EQUAL

    • OP_DUP OP_3 OP_SPLIT OP_DROP OP_1 OP_SPLIT OP_SWAP OP_SPLIT OP_SWAP OP_SPLIT OP_DROP

    • OP_2 <pubkey1> <pubkey2> <pubkey3> OP_3 OP_CHECKMULTISIG

    • OP_DUP OP_HASH160 <hash> OP_EQUALVERIFY OP_CHECKSIG <-

15. Which value do I need to know to validly solve an R-Puzzle?

    • The private key

    • k <-

    • r

    • s

16. Which opcode can be used to reduce the size of the scriptSig component in a transaction pre-image?

    • OP_SIZE

    • OP_PUSH_TX

    • OP_CODESEPARATOR <-

    • OP_RETURN

17. When using OP_PUSH_TX how does the pre-image get generated?

    • You must generate it and insert it into the scriptSig prior to the transaction being submitted on-chain <-

    • Nodes will generate the pre-image for you

    • You don't need a pre-image because that's included as part of the OP_PUSH_TX opcode

    • It is part of the scriptPubKey being spent

18. Does using OP_PUSH_TX make Bitcoin Turing complete?

    • Yes it does

    • No. Bitcoin was already Turing complete, and OP_PUSH_TX is just a more advanced way of using this feature <-

    • Bitcoin is not Turing complete on its own, however OP_PUSH_TX is not the only way to make it turing complete

    • No. It is not possible to make Bitcoin Turing complete.

19. Which hash function is used to create hashPrevouts, hashSequence and hashOutputs in the transaction pre-image?

    • Double SHA256 <-

    • SHA512

    • RIPEMD-160 then SHA256

    • SHA1 then SHA256

20. Which SIGHASH flag must you ALWAYS use?

    • SIGHASH_ALL

    • SIGHASH_SINGLE

    • SIGHASH_ANYONECANPAY

    • SIGHASH_FORKID <-