Chapter 5 assessment 3

1. What is the first field in the transaction pre-image message?

   • nLocktime

   • hashPrevouts

   • nVersion <-

   • prevOutpoint

2. What value is hashed to make hashPrevouts if SIGHASH_ANYONECANPAY is used?

   • Just the parent outpoint for this input

   • All outpoints being spent in this transaction

   • Nothing is hashed. Instead a 32 byte null string is inserted in the field <-

   • Only the input index value is hashed

3. If the sequence value of an input is updated, what happens to a previously created signature

   • The sequence value is updated in the message but the signature is still valid

   • The signature becomes invalid and the input must be re-signed <-

   • The signature can be updated without having to re-do the elliptic curve mathematics

   • As long as a node is told beforehand, the signature stays valid

4. Bob wants to generate a signature that will remain valid even if the sequence number on another input is updated. What SIGHASH flag does he need to use?

   • SIGHASH_ALL

   • SIGHASH_SINGLE

   • SIGHASH_NONE

   • SIGHASH_ALL | SIGHASH_ANYONECANPAY <-