Homework on Public and Private Keys - Questions

[Beasley23]

1. The public key is derived from the private key. So you can send a message that is encrypted using a public key on an open forum and you have to use the private key to see the message.

2. The public key in cryptography works with the digital signature and verifies that the sender is who they are by correlating that the digital signature and public key match which means it is backed by the private key of the sender. This can work with sending and receiving money.

[Wevlin]

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

• a public key is like an address for a person to receive payments that is formulaicly linked to the priv key only known (hopefully) by owner.

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

• secure payments and messaging

[matren]

@ivan

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

The key concept of private key is that there are always two keys that are “magically” tight together and each of those keys can only perform one specific operation. So one key is able to close/lock/encrypt something and only the other key is able to open/un-lock/decrypt something.

@ivan

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

There are 2 basic functionalities: encryption and signing:
In an encryption scenario the key that encrypts is the public one, meaning that anybody knows it and can encrypt the message but not decrypt it with the same key (anyway the sender knows the content already). The only key that can decrypt is the private key. So only the sender and the recipient know the content in the message finally.

Another possible use is to use the private key to sign messages. In this case the message is still readable to anybody but contains your signature (basically a hash created with the private key and the message content). It is possible to use the public key to verify the signature. If the verification succeeds it is even sure to assume that the content has not been changed.

There are 2 pre-requisites involved here to know who signed the message:
a) the senders private key must still be secret to the sender (otherwise somebdy else can sign)
b) the private key you use to verify is really provided by the known sender (otherwise some third-party could exchange the private key with his own one, making you think a specific signature belongs to a specific sender where in this case the sender is someone else).

Both functionalities can be combined together depending on the use case.

[tk115]

1. Your computer will generate a private key, which is a random number. No one but you will know this, you must keep it safe and a secret. From the private key, the public key is generated. This is public and can be shared and seen by others. The public key is used to encrypt information and the private key is what de-crypts the information.

2. Encryption and digital signatures.

[EefjeMuller]

1. Describe the concept of public and private key with your own words.
The public key is derived from your private key and can be shared with others so they can send you a transaction or encrypt a message that only you can decrypt using your private key. You should guard your private key(s) with your life as anyone who knows them can access and steal your money.

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

[sherlock]

1. You create a private key (random number) and from it a public key is created then. Anyone can use it to encrypt and send you a message. But only you have the access to the private key to decrypt respectively verify the message.

2a. Encryption: of messages by using the public key. The recipient can decrypt it by using his private key.
2b.Digital signature: using of a private key as a signature to show that something belongs to you

[Acme-Coyote]

1. You have a key that’s exclusive to you. You can use that key to generate another key, and this key is available to everyone. However, the key that is exclusive to you is cannot be figured out from the key you give everyone.
2. Two use-cases are encryption and digital signatures.

[Mauro]

@iamchaoticcoder

Describe the concept of public and private key with your own words.
Private keys are enormous randomly generated numbers from which the public key is derived. The keys can be used to secure encrypt and decrypt messages.

@PesaCZ

Private key is randomly generated number of a really high value.

@iamchaoticcoder @PesaCZ

There are enormous amounts of private keys. The actual size of one is very small.

A private key is 256 bits long, which takes up 32 bytes. Bits to bytes is (256/8=32)

Here is an interesting website: https://keys.lol/

“This website doesn’t actually have a database of all private keys, that would take an impossible amount of disk space. Instead, keys are procedurally generated on the fly when a page is opened. The page number is used to calculate which keys should be on that page.”

[Mauro]

I am glad you are interested. I changed my goals in these past few years because of crypto. This space is amazing and it gives us many opportunities. Thanks tot his academy its easy to start learning and eventually to become an expert before everyone else.

[Mauro]

That’s alright. The process of getting a public key from the private key is pretty technical. Even I don’t understand it fully. If you really want to go in depth, “Mastering Bitcoin” by Andreas Antonopoulos is a way to start. Keep up the great work.

[Mauro]

@Royy

1. Describe the concept of public and private key with your own words.
   A private key is a random generated number that unlocks everything.

I assume you meant to say that it unlocks your address.

[Mauro]

@gamo7

You share your public key with others, which allows them to send you secret messages.

We actually share public addresses, which are hashed versions of a public key. But all in all, keep up the good work.

[Mauro]

@LAVATOR

! understand this this way : everyone has their own BOX and a KEY to that BOX
BOX-public key
KEY - private key
If I want to send you @ivan a message/money I need to take your BOX, put my content into it and send it to you. You only can open it because you have the KEY to open your BOX.

Good physical example.

[Mauro]

@Yan

You encrypt message with private key and receiver decrypts with your public key.

Its the opposite. There is no point in encrypting a message with a private if everyone can decrypt it with the public key. However you can sign a message with a private key, which would confirm that you own a private key to an certain address without actually reveling it.

[Mauro]

@sherlock

2b.Digital signature: using of a private key as a signature to show that something belongs to you

Very nice set of words used to explain digital signature.

[sherlock]

Thanks buddy

[Rob_McCourt]

1. Private key is the computer generated Key for youre eyes only. Public Key can be seen by everyone on the network.

2. Signatures which can verify that i send the Bitcoin. and Encryption would be the other.

[Royy]

Yes, that’s exactly what I meant. Thanks

[Ciaran]

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

Your computer generates a private key by choosing a random number. The number of different possibilities is so large that it is almost impossible for any 2 computers to randomly generate the same private key. From this private key your computer can derive a public key, which can be shared with other users. It is impossible to take the public and work out the private key.

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

• To encrypt messages - the sender uses the receiver’s public key to encrypt the message. The message can only be read after the receiver’s private key has removed the encryption, so only the receiver can read it.
• To confirm identity - the sender uses their private key to create a digital signature. The receiver can then compare the digital signature to the sender’s public key to see if they were both derived from the same private key. If yes, then it’s the same person.

[rodz]

@ivan

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

1. Public and private keys are used to send confidential information over an open and unsecured network privately using a public key or address with a private key or password.

@ivan

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

2. 2 use-cases for public key cryptography are Encryption and Digital Signatures.