Homework on Public and Private Keys - Questions

[santalittlehelper1]

1 public keys are used for anyone sending messages to you (to your public key)
it is an address to reach you and encrypts the message sent
the private key is the key that unlocks the messages if anyone gets access to this key they have access to whatever crypto, messages etc… you have
2 2 uses for public cryptography
a- a digital signature which is an identifier of the owner
b- verification of sender so i i send email and a digital signature to verify there is no virus or not tampered with or changed i.e. a will or contract

[Mauro]

No problem. Understanding the actual math behind public and private keys can be tricky. The important part is that you learn what is possible and what isn’t. If you are interested in the math behind it, feel free to check the elliptic curve digital signature algorithm. It is well covered in the book called “Mastering Bitcoin” by Andreas Antonopoulos.

[Mauro]

@ArielVB

1.- If I want to send a message to someone and I want to keep that message private then the concept of public and private key it is quite useful.
The software that I’m going to use to send or receive a message, will create a large random number, that number will be my private key. This time I will take literally the meaning of the words “private key” so, I will keep those random numbers in a safe place and I won’t show them to anyone. However, If I want to communicate with the external world, I need a way to do it. That is the job of the public key, to keep me connected to the external world in case someone wants to communicate with me. So, my private key creates my public key to make it easy to people to send me messages. Since my private key creates my public key, there is a direct link between those. So as long as I keep safe my private key I will be able to access to the message that was sent to me through my public key.

Great answer. Feel free to explain how digital signatures work as well. They are really important when it comes to proving that you are the actual owner of a certain address/public key.

[Mauro]

@dbeelow0323

1. Private Key: a randomly selected string to uniquely identify my Wallet . A public key is a secondary way of identifying my wallet (created from my private key) for public transactions. Offers the receiver of my transaction a way to verify my Bitcoin Address to make sure it’s me.
2. Verifying identity of sender and where to send the coins. Where it came from and where it’s going.

In order for you to verify your bitcoin address, you must sign a message with your private key. This digital signature has enough information to determine that you are the owner of a particular public address without every revealing your private key.

What about encryption? Can public and private keys be used in order to send secret messages across a public network?

[Mauro]

@santalittlehelper1

2 2 uses for public cryptography
a- a digital signature which is an identifier of the owner
b- verification of sender so i i send email and a digital signature to verify there is no virus or not tampered with or changed i.e. a will or contract

The second use case is encryption. You explained it in the first question.

[ArielVB]

Thank you Mauro!

So, if someone is reading the whole thread, here are the precisions that Mauro asked me and that I forgot to include.

Taking in consideration the explanation I did of the concept of private key and public key and following the context of Mauro’s comment, the way digital signatures works and the way someone can prove that is the actual owner of a certain address/public key is by transforming that large random number into a 256 bit alphanumeric size. We will use that alphanumeric data as a unique digital signature that will prove that we are the owners of a certain address/public key.

How do we do that? Is not by magic, it’s by pure mathematics, the entire Bitcoin power and security relies on this algorithm call SHA256 that serves among other things as a digital signature. The beauty of this algorithm is that from an input you use in its formula the output is a precise and unique 256 alphanumeric bit piece of data. Remember the large random private key that your computer had created? well, we can use that random number and put it into the SHA256 algorithm and then the output will be your unique signature. Why is it unique? because if you change a single dot of that number the output will be complete different. This is how you can prove that you are the owner of the public address/public key and this is considered as a unique digital signature.

[MisterOgge]

1. you computer genarets a random number, and that is the privet key. and from that privet key it genarates a publik key

2. encryption and digital signature

[LongTermSmoothie]

1. Describe the concept of public and private key with your own words.
   A private key is a number you can randomly generate and keep it private. With cryptography you can then generate a public key, which in turn is also a number. The public key you can show to everyone.
2. What 2 use-cases can public key cryptography be used for?
   Encryption of a message
   Someone who knows your public key can encrypt a message for you and send it to you though unsecure connection. The encrypted message will not make any sense to someone reading this message. Only the owner of the private key will be able to decrypt the message.
   Signing of a document/data/program
   I can sign a document with my private key. From the private key generated public key can then be used by anyone to confirm my ownership (that i have signed this document)

[Mauro]

@ArielVB

How do we do that? Is not by magic, it’s by pure mathematics, the entire Bitcoin power and security relies on this algorithm call SHA256 that serves among other things as a digital signature. The beauty of this algorithm is that from an input you use in its formula the output is a precise and unique 256 alphanumeric bit piece of data. Remember the large random private key that your computer had created? well, we can use that random number and put it into the SHA256 algorithm and then the output will be your unique signature. Why is it unique? because if you change a single dot of that number the output will be complete different. This is how you can prove that you are the owner of the public address/public key and this is considered as a unique digital signature.

It also relies on the public and private key cryptography. Your explanation is almost correct. Let me explain:

In order to make a digital signature we do the following. We take the message we want to sing and hash it. With that hash, we then use our private key to encrypt that data in order to make the digital signature. After that we can use the corresponding public key to decrypt it, and if the hash matches with the message we provided, we can be sure that the data hasn’t been tampered with in some way

With the help of this, miners can be sure that only the owner of the private key can authorize the transactions from an address.

This is all thanks to the Elliptic Curve Digital Signature Algorithm. The function is: y^{2}=x^{3}+ax+b Even I don’t know how fully this works.

[LucianIonescu]

1. the computer generate a random numbers, called private key.
   following certain function public key is generated through private key.

Private key is secret, only the owner has it. is of who own the assets.
Public key can be kn own by everyone in the entire network.

2. the public key can be used in encryption: sender combine the public key of receiver with a secret message, encrypt it in the public network;
   and in digital signature: sender’s digital signature(is generated by private key of sender) and senders’s public key work together, in order to verify the transaction.

[AB-MANDO222]

1.Public keys are available for both you and the party you share with, with public keys the user is able to receive transactions.Private keys are strictly for the user to keep private in order to be able to sign the transactions for receiving crypto coins.
2.one use case for a public key is to sign digital documents; another use case for public key is to receive transactions and sign them digitally.

[Eskild]

Homework on Public and Private Keys - Questions

1. Describe the concept of public and private key with your own words.

One can generate a random number. Say that it is “the private key”. This key is to be kept private, and not shared with anyone. From this number, one can generate a public key, that cannot be used to derive to the private key. This unique key is public and can be shared everywhere.

In bitcoin, a wallet is created in this way:

1. Private key

2. -> Public key

3. -> bitcoin addresses (multiple)

4. What 2 use-cases can public key cryptography be used for?

Use case 1: to encrypt and decrypt messages that are sent and received on public communications networks.

The public key of the recipient of an encrypted message, can be used by senders (combined with their message) so it can only be decrypted by the owner of the public key.

Use case 2: digital signatures for the integrity of a message.

The recipient of a message wants to be able to verify who the message is sent from. If the sender can generate a private and public key, and share their own public key in the message, the recipient can verify that the transaction is “signed” by the sender.

You can not spend bitcoin without signing the transaction with the private key that generated the public key for the addresses in which the bitcoin is “unspent”.

[BISKITBLOKCHOP]

1. Describe the concept of public and private key with your own words.
   Public keys are used to encrypt sensitive information.
   Private key decrypts the information that was encrypted with the use of the public key and acts as your ‘acc number’.

2. What 2 use-cases can public key cryptography be used for?
   Encryption and
   Digital signatures.

[marcetech]

1. The public key is used to encrypt sensitive information and the private key decrypts the information that was encrypted with the use of the public key.
2. The two use cases are: encryption and digital signatures

[ackebom]

1. The core of what makes blockchain possible. There are two main use cases - encryption and Digital signature. Basically private and public keys are tools to make sure we can send secret messages, identify ourselves and ensure the integrity of particular message.
2. Encryption and digital signatures.

[James007]

1. A private key is a random string generated using a particular function, which is kept private; and from which, using a mathematical formula (function) one can generate an associated public key (which is made public), because of a certain mathematical relationship between the public key and private key, and while the public key can be derived from the private key because of this relationship (in addition to other possible manifestations of this relationship), the private key is not derivable from the public key.

2. The two use cases of public and private key technology include:

• Encryption: where a message can be encrypted with the public key the message is being sent to, so the receiver of the message can use their private key to decrypt the message, because of the relationship that exists between the public key and the private key; and

• Digital Signatures: where the integrity of a message and identity of its sender can be verified from the digital signing of the message by the sender and the comparison of the digital signature and the sender’s public key by the receiver using a particular function to determine they are associated.

[Mauro]

Great answers James. Keep up the great work.

[James007]

Thanks Mauro!

[Mauro]

No problem James.

[OhD.Crypto]

1. So the private key is the key no one sees only you. It exists in order to open the public key to which some other derivative can send or transport information. The public key itself generates from your private key. So that if somebody placed info on your public key only you can open it with your private one.
2. Signature, BTC transactions receiving and sending, can be used to encrypt messages