Blocks, chains, and hashing in Blockchain / Solidity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a block with a timestamp.

Blockchain / Solidity

block = {
    'timestamp': [1],
    'data': 'Transaction Data'
}

Drag options to blanks, or click blank then click option'

Achain

Bhashlib.sha256()

Ctime.time()

Dblockchain

Attempts:

3 left

💡 Hint

Common Mistakes

Using a hashing function instead of a timestamp.

Using undefined variables like 'blockchain' or 'chain'.

The time.time() function returns the current time in seconds since the epoch, which is used as the timestamp for the block.

2fill in blank

medium

Complete the code to calculate the hash of a block's data.

Blockchain / Solidity

import hashlib

block_data = 'Sample Block Data'
block_hash = hashlib.sha256([1].encode()).hexdigest()

Drag options to blanks, or click blank then click option'

Ablock_data

Bblockchain

Ctimestamp

Ddata

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to hash undefined variables.

Forgetting to encode the string before hashing.

We hash the string block_data by encoding it first, then applying SHA-256 hashing.

3fill in blank

hard

Fix the error in the code to link the current block to the previous block's hash.

Blockchain / Solidity

current_block = {
    'data': 'Some Data',
    'previous_hash': [1]
}

previous_block_hash = 'abc123def456'

Drag options to blanks, or click blank then click option'

Ahashlib.sha256()

Bprevious_block

Ccurrent_hash

Dprevious_block_hash

Attempts:

3 left

💡 Hint

Common Mistakes

Using the whole previous block instead of its hash.

Using undefined variables.

The previous_hash field should store the hash string of the previous block, which is previous_block_hash.

4fill in blank

hard

Fill both blanks to create a chain of blocks where each block stores the hash of the previous block.

Blockchain / Solidity

blockchain = []

first_block = {'data': 'Genesis Block', 'previous_hash': '0'}
blockchain.append(first_block)

new_block = {
    'data': 'Second Block',
    'previous_hash': [1]
}
blockchain.append(new_block)

print(blockchain[1]['previous_hash'] == [2])

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Ablockchain[0]['previous_hash']

Bblockchain[0]['data']

Cblockchain[0]

Dblockchain[0]['hash']

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong index or field for previous hash.

Confusing data with hash.

The previous_hash of the new block should be the hash of the first block. Here, for simplicity, we link to the first block's hash. The print statement checks if the new block's previous_hash equals the first block's hash.

5fill in blank

hard

Fill the blanks to create a block with data, calculate its hash, and link it to the previous block's hash.

Blockchain / Solidity

import hashlib

previous_block = {'data': 'Block 1', 'hash': 'abc123'}

new_block = {
    'data': [1],
    'previous_hash': [2]
}

block_string = new_block['data'] + new_block['previous_hash']
new_block['hash'] = hashlib.sha256(block_string.encode()).hexdigest()

print(new_block['hash'])

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A'Block 2'

Bprevious_block['hash']

C'abc123'

D'Block 1'

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong string for data or previous hash.

Not concatenating strings properly before hashing.

The new block's data is 'Block 2'. Its previous_hash is the hash from the previous block, accessed as previous_block['hash'].