This is my submission for the Steemit Crypto Academy task by @stream4u and this week its about The Blockchain. Earlier I learned about blockchain and now we have a nice and interesting lesson about CryptoGraphy that helped me to understand more about it in the crypto space.

1-Explain the Blockchain CryptoGraphy and mention a few names which are the Blockchain Platforms (Few names of the Blockchain Platforms)?

What is CryptoGraphy

In simple words, Cryptography means- "the study of secure communications techniques". Its a technology that encryption the information or message which can be accessed by the intended recipient and sender only. This is used to avoid unauthorized access of the information and only the person can access who is authorized to access it and any third person ant access the information.

In technical words, we can say its one of the techniques that help us to safeguard our information from getting accessed by any third party. Blockchain is open and anyone can see the data available on an open platform but with Cryptography this can be used securely where only intended recipients can access it. Cryptography encrypts the message and converts it to ciphertext which no one can read unless decrypted. Its must be decrypted first to read it and that's how this is secured. Decryption is a way to reverse the encryption and this is used with all the communication.

Blockchain CryptoGraphy

We know that blockchain is highly secure and its because blockchain is secured through cryptography. In the blockchain, we can access all open information but whatever is encrypted with Cryptography is not possible to access anyone unless decrypted. Once data has recorded the block then its impossible to alter it and these blocks are connected using cryptographic hash and this makes blockchain highly secure as we know that there is no way to alter the data on the blockchain and before recording, if we change any data then it has to get validated again by nodes before its added to block and once added then there is no way to alter the data.

There is one possible scenario where if one person has 51% of nodes then he/she has that power to change but for any hackers its almost impossible and that way we can say its all so much secure. So this is how cryptography has made blockchain so much secure.

Blockchain Platforms

We have many blockchain platforms as of date and there are a few which are quite popular. Blockchain apps are developed on these platforms and such apps are called dApps. We have two types of blockchain platforms like centralized and decentralized. There are also some which are permission and some are permissionless where one can get access without permission. In fact, STEEM is also a blockchain where we have a bunch of dapps available and we can access them all. Steemit is one of the dapp built on the steem blockchain. Here is the list of some popular blockchain platforms that are in demand scalable.

• Steem
• Ethereum
• EOSIO
• Tron
• Stellar

As I mentioned that there are many platforms but I listed only that are quite popular and out of these ethereum blockchain is on top because of huge development and DeFi. Ethereum is a great platform but transaction fee is something that's crazy here and that's where steem is the leader since there is no transaction fee and transactions get settles almost instantly.

2-Explain the Public Key CryptoGraphy.

Public Key Cryptography is a system that uses pair of keys and this pair consist of a public key and a private key. In this, any person can encrypt the message using the public key and it can be decrypted with the receiver's private key only and this is how pairs of keys are used. The public key can be generated by a private key but there is no way to reverse it.

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For a transaction when two people agree then it can be performed using public and private keys. Its safe and similar to the way we exchange our wallet address or bank account number. We can also verify the digital signature using the private key. In this when a person creates a message using the receiver's public key and sends then this can be decrypted using the receiver's private key only to access it. So its the safest way because no one can have the access to private and public keys altogether.

3-Explain the Private Key CryptoGraphy.

Private Key is a secret code of any wallet which is generated at the time of wallet creation. Not just the private key but the public key is also generated during new wallet creation and we must keep this code secure. We can access cryptocurrencies only using private keys. basically whoever owns the private key is the owner of the wallet and whatever crypto coins the wallet has. The private key is a combination of alphanumeric characters which is not easy to remember and impossible to crack.

When we perform a send crypto transaction then its is signed by the private key and this key remains safe and undisclosed and funds are transferred to the selected wallet address. This key is generated by the system and is much better than a created password because passwords are usually easy to crack for hackers. Funds that are sent to the receiver's wallet can only be accessed using the private key.

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4-Explain the Digital Signature CryptoGraphy and what is Signing Of Transaction/Message?

Digital Signature CryptoGraphy

In simple words, a digital signature is a small data block that we have signed. In the real world, we sign documents using our physical signature to show or prove our agreement. Similarly in the digital world, we use our private and public keys to sign the message using our digital id which includes public and private keys. Here the public key is sent with the file/message and the private key is used to apply with it.

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There are some advantages of using the Digital Signature CryptoGraphy that I am listing down here-

• With a digital signature its easy to sign large data and it does not take too long to sign. This is easy to use with the digital signature cryptography method using the hash value and its security as well.
• This is a secure way as its not possible to modify. If someone tries to alter it then it can be identified during verification that can result in denial. If any of this is changed then it will also reflect in hash value and be easily trackable in case of changes.
• Since with this way we can verify the message using the public key so here we can ensure whether its authentic or not after the verification.
• With digital signature whoever signs it owns the private key so there is a way that person can deny it later.

These are some of the benefits and advantages that we get with digital signatures on documents. We can also use the public key with the document for better transparency and it can be verified as well.

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Signing Of Transaction/Message

This snapshot can help us understand how the process works for digital signatures.

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• Hash algorithm is created using the hash function
• Hash value is created based on data
• Sender uses a private key to sign digitally in the feed of hash value
• Message is signed and attached with data and this is sent to the receiver.
• For signature verification, the public key is used.
• Person who verifies the data use it to generate a hash value.
• Now Hash value is needed to compare with the output value after verification. This outcome will determine whether the signature is valid or invalid.

5-Explain what is Symmetric and Asymmetric cryptography?

Symmetric cryptography

With Symmetric cryptography encryption, only one key is used for encryption and decryption. It is a type of encryption where we use only one key ( secret key) to encrypt and decrypt electronic information. There is a differentiation between a private or public key and a single key is the only secret code that is used with this method.

Symmetric cryptography
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As shown in the above snapshot that plain text is converted to ciphertext using encryption and a secret key is used for this. After the encryption plain text is not in a readable format and it must get decrypted using the same key to get it converted back to plain text. Using the same key makes it easy to perform no need to use multiple keys for this encryption method.

Its a method that can be used between two people who share sensitive or confidential data every day. This way only these people get to know the data and third person would not be able to access it since the decrypted value will not be in a readable format. This can also be used with 2 or more groups of people who are authorized to get the information.

This is useful but again everything comes with advantages and disadvantages so let's go through to understand both sides of it.

Symmetric Cryptography Advantage-
Symmetric Cryptography encryption is highly secure and one of the most used systems. When we use it with the 256-bit key then its extremely secure and not possible to guess it and its almost impossible to crack. This is also easy to do and works faster because its algorithm produces small size files and can be stored internally.

Symmetric Cryptography Disadvantage-

One of the biggest disadvantages of this is sharing data. Encryption keys are not so simple as passwords instead its a tough combination of text and numbers. with this method, we need to have a way to share data with another party.
There is another aspect that if the key is compromised then it can cause bigger damage since only one key is used for encryption and decryption and whoever gets the key can decryption the entire information

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Asymmetric cryptography

This is also known as Public-key cryptography and this system uses pair of keys. Its completely the opposite of what we have seen above. In the previous system we use only 1 key for both the action and here we use pairs of keys to perform decryption and encryption. Hre we use the public and private keys to decrypt the data.

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Let's understand more about it through the diagram. As its is shown we use private and public keys in this method and this is also one of the safest ways to share the data. In this method its necessary to share the public key with another person and its completely secure because the public key doesn't give access to the wallet. If we need to send data to someone then we will ask his public and this key will be attached with data during encryption. Now since the public key is connected with the receiver's private key so the combination of the same private and public key is required to decrypt and if it does not match then it will not be decrypted.

Even the sender can not decrypt it because with a public key only decryption is not possible so its the safest way and only the key holder/receiver can decryption and access the information. Sharing our public key is not a problem but we must not share our private key because its like access that we give to someone if the private key is disclosed.

Asymmetric Cryptography Advantage-
This solves the problem of distributing keys for encryption only public keys are shared and the private key kept secret. Since public key allows to use digital signature then recipients can verify if its from the same send he is expecting from. Here its also possible to check for tampering because for the digital signature public key is used for encryption then the receiver has the option to check message was altered before it is delivered.

Asymmetric Cryptography Disadvantage-

This works slowly as compared with symmetric encryption so if we send bulk messages then it will take quite a long time. With this method, we also have a risk of losing the key and if the key is lost then we won't be able to decrypt the message and even the sender can't help in this case. If a hacker manages to get access to a private key then he can access all messages.

6-How Blockchain Wallets CryptoGraphy works and explains the available types of Crypto Wallets.

How Blockchain Wallets CryptoGraphy works

We know that in the traditional way wallet is something where we keep our funds and our most important reason is to keep our funds. We use the key to make it happen and some people call it locker as well. Now in a digital world where technology has made revolutionary changes so things have become much more smarter and convenient.

A cryptocurrency wallet is a type of software where we can keep our cryptos and get keys to protect the holding. The only way to prove our identity is key so if its lost then we have no access it funds and there is no way to recover it. Every wallet has a unique address and any depositing happening to the wallet address will be received. This wallet address works the same way as a bank account number where we use passwords and pins to keep our funds safe and we share our bank account number to receive the money in the account. Here also we need to share the wallet address to receive the deposit and its completely safe because no one can get access to funds through the wallet address.

We get two types of keys with the wallets-

1-Private Key- This is the secret code that we must not share with anyone and its used to sign the transaction. This is the key to prove wallet ownership.

2-Public Key- Its a key that we can share with the person who is sending data and there is no problem with its sharing. Its used to receive the funds and based on the public key account can be identified.

As I mentioned that wallet address is unique and its impossible to have two wallets with the same address. Its the same like we can't have two bank account with the same number. We require the password to operate a bank account to transfer funds etc and in the same way, we just need a key to send the coin to another wallet. There is no way to send crypto without a key since we would not be able to sign the transaction. Safety of wallet is also the same way life if someone gets our bank account password then it has a risk of losing funds so if we lose our wallet key then here also we have the risk of losing funds.

Bank accounts are controlled by the centralized authority so if we lose the password then it can be recovered by the bank but in crypto its not possible since there is no centralized authority. So if you lost your key then you also lost your access to funds and there is no way to recover it.

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Types of Crypto Wallets

As of now, there are 3 types of crypto wallets-

• Software Wallet
• Hardware wallets
• Paper wallets

Software Wallet

• Desktop Wallet- This type of wallet we can install in a PC or in a browser to perform transactions. These wallets are easy to use and work faster.
• Mobile Wallet- Mobile wallets are much easier to use like PC because more people use a mobile phone and these wallets also work much faster than PC wallets. These are small in size and we can access them on the go and this is the good thing about mobile wallets.
• Online Wallet Now since most of the things are moving to could so crypto wallets are not behind and now we have online wallets that run on the cloud. We need not install anything and it will work the same way. If internet speed is fast then such wallets work much faster. The wax wallet is one such example that I use online without any installation.

Hardware wallets

After software wallets, hardware wallets are safer as we own all the keys and it works offline. This looks like a USB drive by design and is easy to carry. In fact, people prefer to use a hardware wallet if there is a good holding of crypto and keeping all money on an exchange wallet is not safe. Its compatible with various web interfaces and supports all leading crypto coins. This wallet operation is easy and does not require any complex setup and works like a plug-and-play device. ledger is a well-known brand that manufactures hardware wallets.

Paper wallets

This is the safest wallet ever and I have never come across any new or incident where hackers got access to a paper wallet. This is basically a print of keys on the paper and since these keys are not accessible to anyone so its is practically impossible to get access to funds. here we have the print of public and private keys so we can get the receipt of funds using the address printed on paper and private keys are never shared so funds are safe.

7-What are the Merkle trees and What its importance in blockchain?

What is Merkle Trees

It is a data structure that has been used in computer science applications. It was introduced by Ralph Merkle in the year 1979 and it was intended as well. Ralph was a scientist and he was the creator of public cryptography so the name of this data structure is also put on his name. This is the way that made the data verification faster and it contributed to time-saving and made the blockchain data more efficient and secure.

Now its an integral part of the blockchain and its also known as a hash tree. Merkle Trees has helped the blockchain system to get the functionality to have efficient and secure verification of the large data structures. We know that blockchain can now perform fast data verification on vast data this process does not take too long so this credit goes to Ralph Merkle for this innovation.

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Importance of Merkle trees in blockchain?

Its an important part of any blockchain because this method had provided the blockchain to process the data verification faster and reduce the size of the blockchain space. Speed and space both are important parts in any data processing platform because of this innovation blockchain is capable of handling data in scale.

Merkle Trees have four sizable benefits: They provide a way to prove both the integrity and validity of data. They significantly reduce the amount of memory needed to do the above. The required proof and management only needs small amounts of information to be transmitted across networks

Data Verification- It has contributed to make the data processing much faster that is created a bigger impact on the overall functionality of blockchain.

Security- Security is another aspect that has been health Merkle and it ensures that if there is any change in the block then the entire block will be marked as invalid. With this method, we can reply on the blockchain data that whatever is recorded and added to the block is validated.

8-Practical + Theory, do some practical research, study on Blockchain Demo: Public / Private Keys & Signing and then explain the functionality of Key, Signature, Transaction, Blockchain with proper screenshots of yours practical. (Do study well for this topic)

Visit the site provided and I did some research for keys, Signature, Transaction, and Blockchain

Keys-

We discussed asymmetric cryptography that there are two keys including public and private keys. So here we can see both showing on the below snapshot-

Private key- 8458202246180316982724569067530881707272674716355953028063790266736771012388

Public Key- 04f19546238e171dc6ab1963bc85d5a59ba5d2c161b356cf86184ed65a2648600b7d5b0f4ce8a1fc2fa9ed87df79043e2d5989d0e59a056dc9d448312741c6db19

so now we have this and I have clicked on the random button to generate another key-

now I have another public key with different private as shown above.

Private- 90890618047868507990720311789601491251047044559880228830172734071220444526798
Public- 04447d471412379302542a29de9fa92219126985f45499e7b99ab2af5f40d341b6527585ae3a1235b63af1d2cc893ed85358f00e522cc941fa1bc5584a9270f0a0

It means with any different private key there will be different public keys.

Now I have tried manually and entered 987654321 as a private key this is what it is showing-

SO with any change in the private key, the public key will get changed.
private- 987654321
Public- 045ad2703f5b4f4b9dea4c28fa30d86d3781d28e09dd51aae1208de80bb6155beebf9e1170f0849dc49abdcc4ef7b9392bf416a6ea7a316443763829226115a9a7

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Signatures-

I entered the message as "Steem is Awesome" used private key- 987654321 so after a sign, I can see this outcome as message signature-

Message signature- 3045022100d8ccff4072b39cd28ca73504e5ca1235b5f1aafbec84ed56f96648d6c6eb3e4202202dafd6428186d65aab5f1a3cdefd2878fea89214a75daefe9d29fe1f9c6105ee

Now I am trying to verify the transaction with a public key that was generated with private key- 987654321 and it has been verified as the window is in gree color.

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Transactions-

Now let's demonstrate a transfer of $25 and I am using the same private key which I had created before.

From wallet- 045ad2703f5b4f4b9dea4c28fa30d86d3781d28e09dd51aae1208de80bb6155beebf9e1170f0849dc49abdcc4ef7b9392bf416a6ea7a316443763829226115a9a7

To Wallet- 04cc955bf8e359cc7ebbb66f4c2dc616a93e8ba08e93d27996e20299ba92cba9cbd73c2ff46ed27a3727ba09486ba32b5ac35dd20c0adec020536996ca4d9f3d74

Private key- 987654321

Signature- 3046022100b38a70acdd31a8755e07f78f7a4afa1b665bc8500381174ff9ce70ef4dd506990221008bf96f0f7bb5f6203fd3ea23bf8c93635a69c5247290b748d4390a847492fff7

Now, let's verify the transaction-

I went to verify tab and enter the same signature message and clicked on verify. Now its showing in green color that means the transaction is verified.

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Blockchain-

Now will demonstrate some changes in blockchain to see how it behaves if we make changes in the block. here is what I can see now and I will be making changes in block 2. There are 3 blocks visible and connect one after another so the window is showing in green color and its running smoothly.

I have changed the amount and then this has become red and the block is showing invalid and after this block, all are marked invalid as well and in red color.

Now I need to click on mine to validate it and then it will connect with other blocks-

After clicking on mine it will few seconds and now its in green color and the blocks are connected.

9-Conclusion

Blockchain is gaining popularity but without Cryptography, we can imagine a safe, secure and efficient blockchain platform. Cryptography is one of the integral parts of the blockchain and it contributes to making blockchain a sustainable and scalable model that can handle data efficiently.

In this lesson, we learned about symmetric and asymmetric whereas Symmetric use only private key and asymmetric require both private and public keys both. The digital signature is important in crypto transactions and without cryptography, we can sign it.

It is a lesson that is connected with the previous topic which was about blockchain and with each session, I get to know things about blockchain and now with cryptography, I can enhance my knowledge.

It was such a great experience to learn about Cryptography and thanks to the amazing professor for giving us this opportunity and I enjoyed it thoroughly.

Thanks again to professor @stream4u for this great lesson