WEBVTT 1 00:00:00.180 --> 00:00:01.260 In this lesson, 2 00:00:01.260 --> 00:00:03.480 we will learn about Blockchain. 3 00:00:03.480 --> 00:00:08.190 Blockchain is a decentralized, distributed ledger technology 4 00:00:08.190 --> 00:00:12.540 that ensures data integrity and transaction transparency 5 00:00:12.540 --> 00:00:17.100 by recording transactions in a series of immutable blocks. 6 00:00:17.100 --> 00:00:20.130 Immutable means that the blocks are unchangeable 7 00:00:20.130 --> 00:00:21.660 after creation. 8 00:00:21.660 --> 00:00:25.770 An Immutable Database refers to a database where data, 9 00:00:25.770 --> 00:00:30.150 once written, is not able to be altered or deleted. 10 00:00:30.150 --> 00:00:33.690 Immutable databases ensure a permanent record 11 00:00:33.690 --> 00:00:36.000 of blockchain transactions. 12 00:00:36.000 --> 00:00:39.840 Let's learn more about blockchain and immutable databases. 13 00:00:39.840 --> 00:00:43.470 Then, we will conduct a blockchain demonstration. 14 00:00:43.470 --> 00:00:45.720 First, we have blockchain. 15 00:00:45.720 --> 00:00:49.530 Blockchain is a technology that can seem complex, 16 00:00:49.530 --> 00:00:52.530 but is essentially a way to securely record 17 00:00:52.530 --> 00:00:55.470 and share information across a network. 18 00:00:55.470 --> 00:00:57.690 It works like a digital ledger, 19 00:00:57.690 --> 00:00:59.400 similar to a record book 20 00:00:59.400 --> 00:01:01.890 where transactions are written down. 21 00:01:01.890 --> 00:01:05.010 However, unlike traditional ledgers, 22 00:01:05.010 --> 00:01:08.070 blockchain is decentralized and distributed, 23 00:01:08.070 --> 00:01:09.690 meaning it is not controlled 24 00:01:09.690 --> 00:01:12.510 by any single person or organization. 25 00:01:12.510 --> 00:01:13.440 Instead, 26 00:01:13.440 --> 00:01:17.490 it is maintained by a network of computers called nodes 27 00:01:17.490 --> 00:01:18.990 all around the world. 28 00:01:18.990 --> 00:01:23.490 Each transaction or piece of data is recorded in a block. 29 00:01:23.490 --> 00:01:25.080 Once the block is full, 30 00:01:25.080 --> 00:01:27.090 it is linked to a previous one, 31 00:01:27.090 --> 00:01:29.400 forming a chain of blocks, 32 00:01:29.400 --> 00:01:31.590 hence the term blockchain. 33 00:01:31.590 --> 00:01:33.540 What makes blockchain special 34 00:01:33.540 --> 00:01:36.090 is its transparency and security. 35 00:01:36.090 --> 00:01:38.490 Once data is recorded in a block, 36 00:01:38.490 --> 00:01:40.530 it's impossible to change, 37 00:01:40.530 --> 00:01:44.700 providing a tamper-proof record of every transaction. 38 00:01:44.700 --> 00:01:48.510 This feature makes blockchain ideal for situations 39 00:01:48.510 --> 00:01:51.390 where it is crucial to have a transparent 40 00:01:51.390 --> 00:01:53.010 and trustworthy record, 41 00:01:53.010 --> 00:01:56.640 such as financial transactions, voting systems, 42 00:01:56.640 --> 00:01:59.160 or tracking goods in a supply chain. 43 00:01:59.160 --> 00:02:01.020 Every participant in the network 44 00:02:01.020 --> 00:02:03.450 has a copy of the blockchain, 45 00:02:03.450 --> 00:02:06.120 so if someone tries to tamper with the data, 46 00:02:06.120 --> 00:02:09.360 the rest of the network will see that something is wrong, 47 00:02:09.360 --> 00:02:12.660 making blockchain highly resistant to fraud. 48 00:02:12.660 --> 00:02:15.660 Second, we have immutable databases, 49 00:02:15.660 --> 00:02:18.750 and immutable database is a type of database 50 00:02:18.750 --> 00:02:23.700 where the data, once written, cannot be altered or deleted. 51 00:02:23.700 --> 00:02:28.020 A key feature of immutability means that every piece of data 52 00:02:28.020 --> 00:02:32.160 remains exactly as it was when it was first recorded. 53 00:02:32.160 --> 00:02:34.380 Unlike traditional databases 54 00:02:34.380 --> 00:02:36.900 where data can be changed or removed, 55 00:02:36.900 --> 00:02:41.070 immutable databases ensure that a permanent record is kept. 56 00:02:41.070 --> 00:02:43.740 This makes them particularly valuable 57 00:02:43.740 --> 00:02:45.840 in scenarios where it is important 58 00:02:45.840 --> 00:02:50.430 to maintain a historical record without the risk of changes, 59 00:02:50.430 --> 00:02:54.600 such as in compliance, auditing, or legal contexts. 60 00:02:54.600 --> 00:02:57.600 While blockchain is a specific application 61 00:02:57.600 --> 00:02:59.520 of an immutable database, 62 00:02:59.520 --> 00:03:01.920 the two concepts are not the same. 63 00:03:01.920 --> 00:03:06.330 Blockchain uses immutability as one of its core features, 64 00:03:06.330 --> 00:03:10.770 but it also relies on decentralization and cryptography 65 00:03:10.770 --> 00:03:13.590 to provide a secure, transparent way 66 00:03:13.590 --> 00:03:16.260 of managing data across a network. 67 00:03:16.260 --> 00:03:19.110 Immutable databases on their own 68 00:03:19.110 --> 00:03:22.800 do not need to be distributed or decentralized. 69 00:03:22.800 --> 00:03:26.010 They simply ensure that once data is written, 70 00:03:26.010 --> 00:03:27.840 it cannot be modified, 71 00:03:27.840 --> 00:03:31.530 providing a reliable way to preserve information 72 00:03:31.530 --> 00:03:34.110 exactly as it was recorded. 73 00:03:34.110 --> 00:03:38.700 Now, let's demonstrate blockchain on a Kali Linux machine 74 00:03:38.700 --> 00:03:41.970 using an application called Ganache. 75 00:03:41.970 --> 00:03:46.200 Ganache is a personal blockchain for Ethereum development 76 00:03:46.200 --> 00:03:50.280 that we can use to deploy contracts, develop applications, 77 00:03:50.280 --> 00:03:51.870 and run tests. 78 00:03:51.870 --> 00:03:55.890 So while our instance of Ganache will not be made public, 79 00:03:55.890 --> 00:03:58.920 the concepts we can demonstrate would be the same 80 00:03:58.920 --> 00:04:01.980 if it were a publicly distributed blockchain. 81 00:04:01.980 --> 00:04:05.670 For our demonstration, I've installed Node.js, 82 00:04:05.670 --> 00:04:08.880 the Node package manager, and Ganache. 83 00:04:08.880 --> 00:04:10.110 Ganache is running 84 00:04:10.110 --> 00:04:12.120 and we can see that it has provided us 85 00:04:12.120 --> 00:04:13.980 with some starting information. 86 00:04:13.980 --> 00:04:16.290 Here's a breakdown of what we're seeing. 87 00:04:16.290 --> 00:04:20.820 The Available Account section lists 10 Ethereum accounts 88 00:04:20.820 --> 00:04:22.440 that have been created. 89 00:04:22.440 --> 00:04:26.160 Each account has a unique Ethereum address 90 00:04:26.160 --> 00:04:30.870 and an initial balance of 1,000 Ether. 91 00:04:30.870 --> 00:04:33.960 These accounts are used for sending transactions, 92 00:04:33.960 --> 00:04:36.090 deploying smart contracts, 93 00:04:36.090 --> 00:04:38.970 and interacting with the blockchain. 94 00:04:38.970 --> 00:04:43.970 Next, each Ethereum account has a corresponding private key 95 00:04:44.100 --> 00:04:46.770 shown here in hexadecimal format. 96 00:04:46.770 --> 00:04:50.520 These private keys are critical for signing transactions 97 00:04:50.520 --> 00:04:53.250 and proving ownership of accounts. 98 00:04:53.250 --> 00:04:55.170 They're exposed here in Ganache 99 00:04:55.170 --> 00:04:57.660 because it's a development environment, 100 00:04:57.660 --> 00:04:59.490 but in a live blockchain, 101 00:04:59.490 --> 00:05:01.830 private keys must be kept secret 102 00:05:01.830 --> 00:05:05.040 to protect the security of the funds. 103 00:05:05.040 --> 00:05:08.250 Next, the hierarchial deterministic 104 00:05:08.250 --> 00:05:11.580 or HD wallet section shows the mnemonic 105 00:05:11.580 --> 00:05:15.930 or seed phrase used to generate the accounts. 106 00:05:15.930 --> 00:05:18.060 The mnemonic is a set of words 107 00:05:18.060 --> 00:05:21.360 that can recreate the private keys and accounts, 108 00:05:21.360 --> 00:05:25.170 so it must be kept safe in production scenarios. 109 00:05:25.170 --> 00:05:28.560 Next, the default gas prices listed. 110 00:05:28.560 --> 00:05:32.700 Gas prices determine the cost of executing transactions 111 00:05:32.700 --> 00:05:35.850 or smart contracts on the blockchain. 112 00:05:35.850 --> 00:05:38.940 The block gas limit is the maximum amount 113 00:05:38.940 --> 00:05:41.580 of computational work or gas 114 00:05:41.580 --> 00:05:45.780 that can be included in a single block on the blockchain. 115 00:05:45.780 --> 00:05:48.570 It ensures that blocks do not get too large 116 00:05:48.570 --> 00:05:50.940 or expensive to process. 117 00:05:50.940 --> 00:05:55.380 The call gas limit represents the maximum amount of gas 118 00:05:55.380 --> 00:05:59.100 allowed for a single function call or transaction. 119 00:05:59.100 --> 00:06:02.160 This ensures that computational operations 120 00:06:02.160 --> 00:06:05.070 do not exceed reasonable limits. 121 00:06:05.070 --> 00:06:08.220 Finally, we have chain information. 122 00:06:08.220 --> 00:06:10.170 This section provides details 123 00:06:10.170 --> 00:06:12.720 about the blockchain configuration, 124 00:06:12.720 --> 00:06:15.270 including the hard fork being used, 125 00:06:15.270 --> 00:06:16.800 which is Shanghai, 126 00:06:16.800 --> 00:06:20.700 and the chain ID, 1337. 127 00:06:20.700 --> 00:06:25.470 The hard fork refers to a specific set of protocol changes 128 00:06:25.470 --> 00:06:28.740 and updates that are applied to the blockchain. 129 00:06:28.740 --> 00:06:33.090 The chain ID uniquely identifies the blockchain network, 130 00:06:33.090 --> 00:06:37.290 which helps prevent transactions intended for one network 131 00:06:37.290 --> 00:06:40.860 from being accidentally executed on another. 132 00:06:40.860 --> 00:06:45.860 Okay, now we need some way to interact with the blockchain, 133 00:06:46.050 --> 00:06:51.050 so we will install Web3.js with the following command, 134 00:06:51.870 --> 00:06:56.870 sudo npm install web3@1.6.0. 135 00:07:04.200 --> 00:07:05.670 While that's installing, 136 00:07:05.670 --> 00:07:08.583 let me show you the script that I've created. 137 00:07:11.640 --> 00:07:15.933 Cat blockchain_demo.js. 138 00:07:17.250 --> 00:07:21.960 This JavaScript uses the Web3.js library 139 00:07:21.960 --> 00:07:24.930 to interact with a local blockchain. 140 00:07:24.930 --> 00:07:28.320 It demonstrates basic blockchain operations, 141 00:07:28.320 --> 00:07:32.220 such as retreating accounts, checking balances, 142 00:07:32.220 --> 00:07:33.990 sending a transaction, 143 00:07:33.990 --> 00:07:36.840 and displaying transaction details. 144 00:07:36.840 --> 00:07:40.707 The local blockchain is hosted at 127.0.0.1, 145 00:07:42.780 --> 00:07:44.370 or this machine, 146 00:07:44.370 --> 00:07:47.130 on port 8545. 147 00:07:47.130 --> 00:07:51.510 First, this script will retrieve a list of accounts. 148 00:07:51.510 --> 00:07:54.270 These accounts are used to send transactions 149 00:07:54.270 --> 00:07:56.910 and interact with the blockchain. 150 00:07:56.910 --> 00:07:59.820 Next, the script will send the transaction 151 00:07:59.820 --> 00:08:02.790 from the first account to the second account, 152 00:08:02.790 --> 00:08:05.070 transferring one Ether. 153 00:08:05.070 --> 00:08:09.450 The gas limit of this transaction is set to 21,000, 154 00:08:09.450 --> 00:08:11.280 which is the standard amount of gas 155 00:08:11.280 --> 00:08:14.490 required for a simple Ether transfer. 156 00:08:14.490 --> 00:08:17.160 After the transaction is successful, 157 00:08:17.160 --> 00:08:20.220 the script prints out the transaction hash, 158 00:08:20.220 --> 00:08:24.480 which uniquely identifies the transaction on the blockchain. 159 00:08:24.480 --> 00:08:26.790 After sending the transaction, 160 00:08:26.790 --> 00:08:30.720 the script checks the updated balance of the first account 161 00:08:30.720 --> 00:08:33.840 to show the impact of the transaction. 162 00:08:33.840 --> 00:08:38.160 Finally, the details of the transaction will be displayed. 163 00:08:38.160 --> 00:08:42.570 Now, let's run this script using the following command, 164 00:08:42.570 --> 00:08:47.570 sudo node blockchain_demo.js. 165 00:08:55.230 --> 00:08:56.130 Okay. 166 00:08:56.130 --> 00:08:58.950 Here's a breakdown of what we're seeing. 167 00:08:58.950 --> 00:09:01.200 The Available Accounts section 168 00:09:01.200 --> 00:09:04.380 lists our 10 Ethereum accounts. 169 00:09:04.380 --> 00:09:07.230 Each account has a unique address 170 00:09:07.230 --> 00:09:10.890 which serves as its identifier on the blockchain. 171 00:09:10.890 --> 00:09:15.600 Next, we see the initial balance of the first account, 172 00:09:15.600 --> 00:09:18.330 which is 1,000 Ether (ETH). 173 00:09:18.330 --> 00:09:23.040 Next, we see a transaction successful hash. 174 00:09:23.040 --> 00:09:24.090 This indicates 175 00:09:24.090 --> 00:09:27.510 that a transaction was successfully completed. 176 00:09:27.510 --> 00:09:31.500 The transaction hash uniquely identifies this transaction 177 00:09:31.500 --> 00:09:34.590 on the blockchain and serves as a reference 178 00:09:34.590 --> 00:09:37.140 for querying the transaction details 179 00:09:37.140 --> 00:09:40.530 and proves the transaction was recorded. 180 00:09:40.530 --> 00:09:44.910 Next, we see a new balance of the first account, 181 00:09:44.910 --> 00:09:49.800 which is updated to approximately 999 ETH 182 00:09:49.800 --> 00:09:52.440 due to 1 ETH being sent 183 00:09:52.440 --> 00:09:56.700 and the gas fee charged for processing the transaction. 184 00:09:56.700 --> 00:10:00.090 Last, we see the Transaction Details. 185 00:10:00.090 --> 00:10:02.100 We won't review them all, 186 00:10:02.100 --> 00:10:06.120 but there are a few that are relevant to our discussion. 187 00:10:06.120 --> 00:10:09.990 The Block Hash and Block Number indicate the block 188 00:10:09.990 --> 00:10:12.480 where the transaction was recorded. 189 00:10:12.480 --> 00:10:15.600 Next, the transaction index. 190 00:10:15.600 --> 00:10:19.410 This is the position of the transaction within the block. 191 00:10:19.410 --> 00:10:21.690 From and To: 192 00:10:21.690 --> 00:10:25.290 These are the sender and receiver addresses. 193 00:10:25.290 --> 00:10:27.540 Next, we have a Value: 194 00:10:27.540 --> 00:10:30.930 This is the amount of Ether that has been transferred 195 00:10:30.930 --> 00:10:33.240 specified in wei. 196 00:10:33.240 --> 00:10:37.020 Then we see the Gas Price and the Gas. 197 00:10:37.020 --> 00:10:40.140 This indicates the computational cost 198 00:10:40.140 --> 00:10:45.140 for processing the transaction and the fee per unit of gas. 199 00:10:45.480 --> 00:10:48.570 Finally, v, r, and s: 200 00:10:48.570 --> 00:10:50.580 These values are used 201 00:10:50.580 --> 00:10:53.610 in the digital signature of the transaction, 202 00:10:53.610 --> 00:10:56.850 proving it was signed by the sender. 203 00:10:56.850 --> 00:11:01.290 But all we are seeing here is a single transaction. 204 00:11:01.290 --> 00:11:03.390 Let's take a look at the ledger. 205 00:11:03.390 --> 00:11:05.850 All transactions can be summarized 206 00:11:05.850 --> 00:11:09.480 by querying the blockchain to observe transactions. 207 00:11:09.480 --> 00:11:11.940 So I've created a separate script 208 00:11:11.940 --> 00:11:13.710 that will query the blockchain 209 00:11:13.710 --> 00:11:16.200 and provide us with a summary of transactions 210 00:11:16.200 --> 00:11:17.400 that have occurred. 211 00:11:17.400 --> 00:11:19.200 Before we run this script, 212 00:11:19.200 --> 00:11:21.570 let's do one more transaction, 213 00:11:21.570 --> 00:11:24.960 that way we have a little more data to look at. 214 00:11:24.960 --> 00:11:28.050 We'll do this by rerunning the command 215 00:11:28.050 --> 00:11:32.743 sudo node blockchain_demo.js. 216 00:11:34.500 --> 00:11:38.070 Next, let's take a look at our ledger. 217 00:11:38.070 --> 00:11:43.070 We'll do this by running the sudo node ledger.js command. 218 00:11:48.270 --> 00:11:50.610 Okay, here's what we're seeing. 219 00:11:50.610 --> 00:11:54.330 We can see the details about the most recent blocks 220 00:11:54.330 --> 00:11:55.680 of our blockchain, 221 00:11:55.680 --> 00:11:59.610 along with the transactions contained within these blocks. 222 00:11:59.610 --> 00:12:02.190 Here we're viewing our ledger. 223 00:12:02.190 --> 00:12:05.280 We can see the latest block number, 224 00:12:05.280 --> 00:12:07.950 which indicates that block two 225 00:12:07.950 --> 00:12:11.190 is the most recent block in the blockchain. 226 00:12:11.190 --> 00:12:14.880 The number represents the sequential order of blocks, 227 00:12:14.880 --> 00:12:18.363 starting from the genesis block, block 0. 228 00:12:19.200 --> 00:12:23.250 Then we can see the block 2 details, 229 00:12:23.250 --> 00:12:25.500 including the block number, 230 00:12:25.500 --> 00:12:28.050 which is the block's position in the chain, 231 00:12:28.050 --> 00:12:31.140 and the hash for block 2. 232 00:12:31.140 --> 00:12:33.750 Each block in the blockchain is hashed. 233 00:12:33.750 --> 00:12:37.020 A hash is a cryptographic representation 234 00:12:37.020 --> 00:12:38.700 of the block's data, 235 00:12:38.700 --> 00:12:40.920 essentially a digital fingerprint 236 00:12:40.920 --> 00:12:43.680 that uniquely identifies the block. 237 00:12:43.680 --> 00:12:47.220 What makes blockchain truly secure and immutable 238 00:12:47.220 --> 00:12:50.190 is that each block also includes the hash 239 00:12:50.190 --> 00:12:52.860 of the previous block in the chain. 240 00:12:52.860 --> 00:12:55.500 This creates a link between blocks, 241 00:12:55.500 --> 00:12:59.010 forming a continuous tamper-proof chain. 242 00:12:59.010 --> 00:13:03.120 If any information in a block is altered, even slightly, 243 00:13:03.120 --> 00:13:05.190 the block's hash will change. 244 00:13:05.190 --> 00:13:08.970 Since each block contains the previous block's hash, 245 00:13:08.970 --> 00:13:11.160 any change would break the link, 246 00:13:11.160 --> 00:13:14.910 alerting the network that tampering has occurred. 247 00:13:14.910 --> 00:13:17.160 This interconnected structure 248 00:13:17.160 --> 00:13:19.950 means that to alter any single block, 249 00:13:19.950 --> 00:13:22.080 a malicious actor would need to change 250 00:13:22.080 --> 00:13:23.970 all subsequent blocks, 251 00:13:23.970 --> 00:13:26.130 recalculate all hashes, 252 00:13:26.130 --> 00:13:28.320 and gain control of the majority 253 00:13:28.320 --> 00:13:30.510 of the network's computing power, 254 00:13:30.510 --> 00:13:33.390 which is practically impossible. 255 00:13:33.390 --> 00:13:36.570 This reliance on previous block hashes 256 00:13:36.570 --> 00:13:39.060 is what makes blockchain immutable 257 00:13:39.060 --> 00:13:41.640 as it safeguards the entire chain 258 00:13:41.640 --> 00:13:44.160 from unauthorized modifications, 259 00:13:44.160 --> 00:13:46.890 ensuring that once data is recorded, 260 00:13:46.890 --> 00:13:49.590 it remains permanent and secure. 261 00:13:49.590 --> 00:13:53.280 Finally, we have a transaction hash. 262 00:13:53.280 --> 00:13:55.350 This identifies the transaction 263 00:13:55.350 --> 00:13:58.170 and some details about the transaction, 264 00:13:58.170 --> 00:14:02.220 including the transaction parties, the amount transferred, 265 00:14:02.220 --> 00:14:04.260 and the gas used. 266 00:14:04.260 --> 00:14:06.600 As we continue to look down the output, 267 00:14:06.600 --> 00:14:10.320 we can see our first transaction in block number one, 268 00:14:10.320 --> 00:14:13.020 and we can see block 0. 269 00:14:13.020 --> 00:14:16.320 Block 0 is known as the genesis block, 270 00:14:16.320 --> 00:14:19.200 it's the first block in the blockchain. 271 00:14:19.200 --> 00:14:22.530 The genesis block contains no transactions, 272 00:14:22.530 --> 00:14:26.370 which is typical since it primarily serves as the foundation 273 00:14:26.370 --> 00:14:28.530 for all subsequent blocks. 274 00:14:28.530 --> 00:14:31.470 This demonstration showed us the concept 275 00:14:31.470 --> 00:14:36.000 of blockchain's immutability and distributed ledger. 276 00:14:36.000 --> 00:14:39.000 It showed how blocks are sequentially late, 277 00:14:39.000 --> 00:14:41.880 each containing unique transactions. 278 00:14:41.880 --> 00:14:45.450 Additionally, based on each block containing data 279 00:14:45.450 --> 00:14:47.340 from the previous blocks, 280 00:14:47.340 --> 00:14:51.390 we showed that data recorded in a block is immutable, 281 00:14:51.390 --> 00:14:55.110 maintaining a secure and transparent record 282 00:14:55.110 --> 00:14:57.270 of all transactions. 283 00:14:57.270 --> 00:14:59.310 So remember, 284 00:14:59.310 --> 00:15:02.820 blockchain is a decentralized technology 285 00:15:02.820 --> 00:15:06.720 that records data in a secure and transparent way 286 00:15:06.720 --> 00:15:09.240 across a network of computers. 287 00:15:09.240 --> 00:15:11.220 It acts like a digital ledger 288 00:15:11.220 --> 00:15:13.980 where transactions are stored in blocks, 289 00:15:13.980 --> 00:15:15.930 and once a block is full, 290 00:15:15.930 --> 00:15:18.030 it is linked to the previous one, 291 00:15:18.030 --> 00:15:20.610 creating an unchangeable chain. 292 00:15:20.610 --> 00:15:24.420 The key feature of blockchain is its immutability, 293 00:15:24.420 --> 00:15:28.260 meaning once data is recorded, it cannot be altered, 294 00:15:28.260 --> 00:15:31.860 ensuring a trustworthy and tamper-proof record. 295 00:15:31.860 --> 00:15:34.560 Immutable databases, on the other hand, 296 00:15:34.560 --> 00:15:37.170 are systems where data, once written, 297 00:15:37.170 --> 00:15:39.330 cannot be changed or deleted, 298 00:15:39.330 --> 00:15:43.470 preserving information as it was originally recorded. 299 00:15:43.470 --> 00:15:46.500 While blockchain uses immutable databases 300 00:15:46.500 --> 00:15:48.180 as a core component, 301 00:15:48.180 --> 00:15:52.290 it also includes decentralization and cryptography 302 00:15:52.290 --> 00:15:55.170 to add security and transparency 303 00:15:55.170 --> 00:15:57.663 across its entire network.