Following one digital currency transaction through the blockchain

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Date:

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Quick Questions

Shade in the A or B circle for each question.

1. Which step happens FIRST when a digital currency payment is sent?

A The block joins the chain

B The sender makes the payment (the transaction)

2. What happens to a transaction straight after it is made?

A It is time-stamped with the date and time

B It is deleted from the network

3. Which is the correct order for one transaction?

A Block, chain, transaction, time-stamp

B Transaction, time-stamp, block, chain

4. Where is a time-stamped transaction placed before it becomes part of the chain?

A In a block with other transactions

B In the sender's digital wallet only

5. What happens once a block is full of time-stamped transactions?

A The block is added to the end of the chain

B The block is sent back to the sender to be changed

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1sender -> payment		AThe steps at the end are the wrong way round. The transaction goes into a block first, and then the block joins the chain.
2payment -> time-stamp		Bblock -> chain -> permanent
3The time-stamped transaction is stored together with other transactions in a group		CThe transaction is given the exact date and time it was made, so its place in the order is fixed
4Once the block is joined to the end of the blockchain, the record is permanent		DThe time-stamp is added too late. The transaction must be time-stamped before it is placed in a block.
5payment -> block -> time-stamp -> chain		EThe first step: the sender makes a payment, which creates a new transaction
6payment -> time-stamp -> chain -> block		Ftransaction -> block

Definitions

transaction -> time-stamp -> block -> chain

Fill in the Blanks

Complete each line of code by filling in the missing parts.

Step 1: sender makes a payment Step 2: payment is ____________ Step 3: payment is put in a block

Step 1: sender makes a transaction Step 2: transaction is time-stamped Step 3: transaction is placed in a _____

Step 3: transaction is placed in a block Step 4: the block joins the _____ Step 5: the record is permanent

The ______ makes the payment The payment is time-stamped The payment is placed in a block

Step 4: the block joins the chain Step 5: the record is now _________

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A sender ← 'Ava'

B payment ← MAKE(sender, 20)

C payment.time ← ERASE()

D block.ADD(payment)

Question 2

A payment ← MAKE('Ava', 20)

B payment.time ← NOW()

C chain.ADD(payment)

D chain.ADD(block)

Question 3

A payment ← MAKE('Ben', 15)

B payment.amount ← NOW()

C block.ADD(payment)

Question 4

A IF payment.time ≠ NULL THEN

B block.ADD(payment)

C chain.REMOVE(block)

D ENDIF

Question 5

A payment ← DELETE('Dee', 30)

B payment.time ← NOW()

C block.ADD(payment)

Answer Key

Following one digital currency transaction through the blockchain

Section A: Quick Questions

B — The sender makes the payment (the transaction)

A — It is time-stamped with the date and time

B — Transaction, time-stamp, block, chain

A — In a block with other transactions

A — The block is added to the end of the chain

Section B: Match the Pairs

sender -> payment → The first step: the sender makes a payment, which creates a new transaction

payment -> time-stamp → The transaction is given the exact date and time it was made, so its place in the order is fixed

The time-stamped transaction is stored together with other transactions in a group → transaction -> block

Once the block is joined to the end of the blockchain, the record is permanent → block -> chain -> permanent

payment -> block -> time-stamp -> chain → The time-stamp is added too late. The transaction must be time-stamped before it is placed in a block.

payment -> time-stamp -> chain -> block → The steps at the end are the wrong way round. The transaction goes into a block first, and then the block joins the chain.

Section C: Definitions

transaction -> time-stamp -> block -> chain — The order a payment follows: the sender makes it, it is time-stamped, placed in a block, and the block joins the chain, so the record becomes permanent.

Section D: Fill in the Blanks

Step 1: sender makes a payment
Step 2: payment is time-stamped
Step 3: payment is put in a block

Step 1: sender makes a transaction
Step 2: transaction is time-stamped
Step 3: transaction is placed in a block

Step 3: transaction is placed in a block
Step 4: the block joins the chain
Step 5: the record is permanent

The sender makes the payment
The payment is time-stamped
The payment is placed in a block

Step 4: the block joins the chain
Step 5: the record is now permanent

Section E: Spot the Error

C — The payment must be time-stamped with the current time, so the line should be payment.time ← NOW(). Erasing the time would leave no record of when it happened.

C — A payment is placed in a block first. The chain is built from blocks, not single payments, so the line should be block.ADD(payment).

B — The time-stamp belongs in the time field. It must not overwrite the amount, so the line should be payment.time ← NOW().

C — Once a payment is in a block, the block joins the chain. It is not removed from it. The line should be chain.ADD(block).

A — A transaction starts when the sender makes a payment, so the line should use MAKE. A deleted payment can never be time-stamped or added to a block.