Blockchain Project

By Phillip Boll

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This readme file contains information regarding many aspects of the project, one of the first things you must do before attempting to run it is to install the openssl library. This library is used for the encryption in the blockchain. I am using SHA256, the most up-to-date 512 bit encryption

Single vs Multi Threading

1. The goal for this program is to achieve multi threading during mining of blocks in the blockchain

2. Multi threading is essentially where we run multiple asepcts of this program on different processors side by side

3. Multi threading is necessary for blockchain especially when the difficulty of finding hashes increases past 2-3 leading zeroes

4. NEW UPDATE, At the current time (Fri Sep 27) Multi threading has been IMPLEMENTED

Hashing (SHA256):

1. SHA256 is the cryptographic hashing function, the same used in cryptocurrencies like Bitcoin.

2. Some of the characteristics are the following: 2a. Fixed Length: Output is always a 64 char hex 2b. The same input produces the same output, always 2c. Small changes in input will cause majorly different output 2d. You cannot reverse engineer it 2e. Every output is unique to its input(no two inputs create same output)

3. So how is it used in this project? (rhetorical question) : 3a. Previous Block Hash 3b. Transaction history 3c. Nonce

   These are all used to determine a unique hash

4. We combine the previous hash, nonce, timestamp and other data available into a string. Then the SHA256 algorithm is used to hash the string. The result is a unique identification we can use to find the block and link it in the chain.

5. If any block is changed, the hash will also change making it immune to hacking since this will invalidate the block chain.

6. What you're probably thinking: "WOW phillip, you explained this so well!!!"

Transaction Verification (Merkle Tree Proofs):

How we verify transactions via the Merkle Tree

1. The top node in the tree is known as the merkle root

2. The root is the result of recursive hashing of nodes, if any node changes then the root changes

3. If any node changes then the transactions have changed

4. To verify a certain transaction, we generate what is known as a Merkle Proof

5. A merkle Proof consists of hashes which are required to remake the tree from transaction being verified and up to the root again '

6. Using the proof and the hash from the transaction, we remake the root and compare it to the original Merkle Root.

7. If the roots match, the transaction is verified.

Transactions (timestamps):

1. Transactions follow ISO8601 Format which is YYYY-MM-DD followed by the time
2. An example of the format is: 2024-09-11T15:30:00Z
3. The "T" separates the date from the time
4. The "Z" at the end of the time is to denote what time zone it is. We are using UTC (Universal Timezone Coordinates)
5. The purpose of timestamps is to keep track of transactions which is why each block in the blockchain contains a list of transactional timestamps

WARNING: Transactions are not in a readable format unless you convert them with ctime function, for example they'll pop up like this:

Transactions: 1726520457

You can read them with this if you'd like: ctime(&(current->transactions));

How I create my executables (This depends on your system since OpenSSL gets tricky depending on where your computer stores it):

g++ -o exec main.cpp -I/opt/homebrew/opt/openssl@3/include -L/opt/homebrew/opt/openssl@3/lib -lssl -lcrypto

The most up-to-date executable for using the database:

g++ -std=c++17 -o exec main.cpp db.cpp blockchain.cpp multithread.cpp
-I/opt/homebrew/opt/openssl@3/include
-I/opt/homebrew/opt/postgresql@14/include
-I/opt/homebrew/include
-L/opt/homebrew/opt/openssl@3/lib
-L/opt/homebrew/opt/postgresql@14/lib
-L/opt/homebrew/opt/libpqxx/lib
-lssl -lcrypto -lpqxx

g++ -std=c++17 -o exec server.cpp db.cpp blockchain.cpp multithread.cpp
-I/usr/include/openssl
-I/usr/include/postgresql
-I/usr/include/jsoncpp
-L/usr/lib/x86_64-linux-gnu
-lpqxx -lssl -lcrypto -pthread -ldrogon -ljsoncpp -ltrantor

The above is used for including Drogon, which I am used to create an API for my backend that connects to my Terminal UI in javascript

./exec

Transferring Executable API file from blockchain project to EC2 Instance on AWS

scp -i /Users/phillipboll3/Desktop/SSH/blockchain-frontend.pem /Users/phillipboll3/Desktop/Blockchain/src/exec [email protected]:/home/ubuntu/

Compiling the project on the EC2 Instance

g++ -std=c++17 -o exec server.cpp db.cpp blockchain.cpp multithread.cpp
-I/usr/include/openssl
-I/usr/include/postgresql
-I/home/ubuntu/Crow/include
-L/usr/lib/x86_64-linux-gnu
-lpqxx -lssl -lcrypto -pthread

POW (Proof of Work ):

1. For this project, proof of work will usually be set to an easy-medium level since we want to simply showcase my understanding of how blockchain works

2. For those who don't understand POW, the more leading 0's you have in your hash requirements, the harder it becomes for your program to generate a valid hash

3. Easy Difficulty hashes usually have between 1 and 3 leading zeros. 3 leading zeros means only 1 in 4,096 hashes are going to be valid for adding a block to the blockchain

4. Medium Difficulty is between 4 and 6 leading zeros. 6 leading zeros means only 1 in over 16 million hashes will be valid.

5. Hard Difficulty is between 7 and 9 leading zeros. 9 leading zeros means only 1 in over 68 billion (WOW) hashes will be valid for the blockchain.

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The following is an image showing the mining of an 8 leading zeros hash, taking approximately 18 minutes. Anything higher would take hours to day to mine with single threading on a macbook.

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Single Threading Example:

Multi Threading Now :

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USING THE SQL DATABASE (POSTGRESQL):

1. I am using postgresql for my database since it is widely used in industry compared to mysql and supports a broader range of languages

2. Simply put, I created a .cpp and .h file for inserting into the database blocks after mining from our doubly linked list blockchain in c++

3. The following are some simple commands to use if you are new to postgresql:

Connecting to PostgreSQL:

psql -d database // in this case database is just the name of the database i created

Executing SQL File:

\i path/to/database.sql

\i /Users/phillipboll3/Desktop/Blockchain/ src/database.sql

Verifying that the table was created and exists:

\dt

W3 Schools is a great source for learning SQL, I used that school to learn what I know about SQL for this project:

https://www.w3schools.com/sql/sql_create_table.asp

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Connecting PostgreSQL to C++ Blockchain:

1. We use another library called pqxx
2. Pqxx connects the two and allows us to call functions in C++ which insert data directly into our database
3. The port, username, and password are required to do so.
4. You can check the default port being used by PostgreSQL through the command:

cat $(brew --prefix)/var/postgresql@14/postgresql.conf | grep port

5. The default for me: 5432

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Common Workflow for accessing database after running executable:

brew services start postgresql@14 psql -U phillipboll3 -d database SELECT * FROM blocks;