Homework on Public and Private Keys - Questions

Blockchain and Bitcoin 101
#4668

Should you not use another example than the Bob and Alice example or what am I missing? When you send a transaction on the bitcoin network everybody can see it so how can it be private?Not everybody can access to use the funds but everybody can see how much is sent and to which address and from which address?

#4669

No one said tx on Bitcoin are private. All transactions are visible on the network for everyone to see.

#4670

In order for Alice to send a private message to Bob she needs to encrypt the messageā€¦this message becomes unreadable,nobody else can read itā€¦or am I missing the point?Does it just mean that when she sends bitcoin to bob only he can get access to the bitcoin?

#4671

  1. Private key is the mother. With a certain encryption algorithm, the father, you produce a son (public key). This son comes out to the world and is very famous so everyone knows him. However a person canā€™t know who the mother is, because she is hidden in a random place and no one know who she is. The mother wants to send bitcoin to a certain person in a planet. So she creates a special son that is easily recognizable with the other son. The person who receives the bitcoin wants to verify it was the mother who sent it. So he compares this special son (digital signature) with the very famous son and concludes they come from the same mother.

  2. Encryption and Digital Signatures

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#4672
  1. Describe the concept of public and private key with your own words.

A public and private key are both very large numbers. The private key is generated as a random number, then the public key can be derived from the private key. However the private key cannot be derived from the public key so the public key is safe to share.
The keys have a mathematical relationship such that they can be used to safely encrypt communication or to digitally sign data.

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

  1. Encryption - it is possible for different actors to communicate over a public network in secret without sharing any information beforehand. Only the public key needs to be sent and then it can be used to create encrypted messages which only the holder of the private key can decrypt.

  2. Digital signatures - it is possible to sign any content using the private key, such that someone else could verify that the content could only be sent by the holder of the private key. This is how Bitcoin transactions work.

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#4673
  1. Describe the concept of public and private key with your own words.
    if you generate a random number and hold it as your PVK then use PVK to produce a PBK as well as sign a message to someone. Then recipient without knowing the PVK can confirm that the msg was sent by the same PVK that produces the Signature.
  2. What 2 use-cases can public key cryptography be used for?
    Encryption and Digital Signature
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#4674
  1. Private key is your personal number randomly created that only you have access to. A public key is created from the private key and can be seen by all . The private key decrypts the public keys message
  2. Public key cryptography can be used for encryption and digital signatures.
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#4675

1.The public key is for the encryption of a message/transaction and the private key is for the decryption of a message/transaction.

2.Encryption and DigitalSignatures

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#4676

Yes you are right this is called encryption. Encoding some information in a way that you and some trusted person have an access to get that information is called encryption. and for the third party itā€™s just like trash until they get the decryption function.

When Alice sends bitcoin to bob, to do this she uses her private key to sign a message with the transaction-specific details, and this message is then sent to the blockchain and contains an:
input: the source transaction of the coins previously sent to Aliceā€™s address
amount: some amount of BTC to be sent from Alice to Bob
output: Bobā€™s public address.
This transaction is then broadcast to the Bitcoin network where miners verify that Aliceā€™s keys are able to access the inputs she claims to control. And after that gets confirmed then Bob can spend the coins he received. This is the use case of digital signature in the bitcoin protocol.

#4677
  1. Describe the concept of public and private key with your own words.

private key: A randomly generated number by the owner to be kept secret.
public key: A generated number using the private key that can be shared for uses such asā€¦

  1. What 2 use-cases can public key cryptography be used for?
  1. Encryption.
  2. Digital Signatures.
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#4678

Describe the concept of public and private key with your own words.
Private key is a randomly generated sequence of letters and numbers. From the Private key is generated a Public key of letters and numbers. The Private key allows the owner to encrypt and digitally sign a transaction. The Public key allows for verification that the transaction came from the Private key owner. Private keys are to be kept just as their namesake suggests, private to the owner. The Public keys, which also are the address of the owner are to be given out. They allow for transactions to be encrypted by those wanting to send the owner crypto.
What 2 use-cases can public key cryptography be used for?
Can be used for encryption and Identity verification.

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#4679

Thanks a lot for the reply.My main confusion is in the way Ivan mentions the message between Bob and Alice being private and impossible to read though when Bitcoin messages are sent everybody can see the transactions.Am I looking at it in the wrong way?

#4680

A private key is a key known only to the holder. It should not be shared. A public key is a key shown to everyone; there is no need to hide it. Your public key is derived from a private key.

Public and private keys are used in encryption and digital signatures to ensure security.

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#4681

The messages on the blockchain are digitaly signed, nothing is encrypted. At least not on in case of the Bitcoin blockchain.

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#4682

So what does Ivan mean with his Alice and Bob messaging example in the Public and Private key cryptography in blockchain and bitcoin 101?

#4683

  1. The private key is a random generated number and from this number you generate your public key and you digital signature. With your Digital Signature and public key other people can confirm that you (the person who has the private key) is really you. So you are able to confirm transactions with your Digital signature and public key.

  2. Encryption and Digital Signature

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#4684
  1. Public keys are meant for people to see so that they know youā€™re identity and private keys are used for private things such as messages and holding your crypto

2.public key cryptography can be used for encrypting messages and transactions

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#4685
  1. Describe the concept of public and private key with your own words.

Public Key allows you to share your encrypted message on an open network. The private key allows the unlocking of the encryption linked to the specific Public key.

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

1: Encryption
2: Digital signature.

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#4686

  1. A private key is a randomly generated number. The public key is derived from the private key using a one-way calculation such that the private key cannot be derived from the public key.

  2. Two use cases for public key encryption are to a) encrypt the contents of a message or communication itself so that it cannot be read without decryption or b) Providing a digital signature of a message to confirm the identity of the sender.

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#4687

1.) The public key is for everyone to see. Could be a website,blog, etc
The private key is something meant only to the recipient like a private message.
2.) The two use cases are for encryption and a digital signature

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