Homework on Public and Private Keys - Questions

Blockchain and Bitcoin 101
#3283
  1. Describe the concept of public and private key with your own words.

Public and private keys are means to encrypt and digitally sign data. One uses a public key to encrypt data that can only be decrypted with the corresponding private key or one signs data with their private key which can only be verified by using the corresponding public key.

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

To encrypt private messages being sent over a public network, or in the case of bitcoin to digitally sign transactions to verify who is initiating the transaction and if they have the funds to enact such a transaction

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#3284

Love the work, way beyond me right now.

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#3285
  1. A private key is personalized to a single person and is hidden from everyone else. That private key can be used to generate a public key that is displayed to the world. This public key can then be used to verify that a message was sent from its originator (digital Signature) but without decrypting the message. Then the private key is used to decrypt the message for the receiver.
    Similar to a Hash, it is one way, where you can use the private key to get a public one. You canā€™t use the public key to determine the private one.
  2. Sending encrypted/private messages between parties and digital signatures.
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#3287

Thank you so much for pointing it out. I actually went back and rewatch this lecture. It feels good to know someone is really reading and watching over. I do get in now
:slight_smile:

#3288

  1. Describe the concept of public and private key with your own words.
    Public and private keys are both random numbers. A unique public key can be generated from a private key, but the reverse is not true. The public and private keys have different functionality depending on the use.

  2. What 2 use-cases can public key cryptography be used for?
    The first use-case described in the lecture is encryption. Apparently, it is possible to encrypt a message using a public key that is only possible to decrypt using the private key. That means any person can send a secret message to someone using his public key, but only he can read it using his secret private key.
    The second use-case discussed in the lecture is electronic signatures. Somehow it is possible to show than an electronic signature and a certain public key were both generated using the same private key without knowing what that private key is.
    It is important in both cases that the private key is secret, because otherwise the message would not be secret or the signature could be forged.

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#3289

The private key is a digital signature that encrypts the identity of its owner. The public key, which is generated from the private key, is used to verify its correspondence with the private key and thus verify that both belong to the same wallet.

The two use cases for public keys are encryption (the need to encrypt sensitive information) and digital signatures (identifying the origin of an encrypted message and ensuring the integrity of the message).

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#3290
  1. The private key is a random number created once you made a new wallet. The private key have to be secret and only the owner of the wallet have to know that number.

The public key is a number derivate of your one private key. The public key can be shared whit others so they can send you messages or data.

  1. To do your digital signature and to decrypt massages encrypted whit your public key.
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#3291

1 private key is random number and public key is derived from the private key. Public key can be used publicly and private key is only used privately
2 to encrypt messages in emails or transactions

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#3292
  1. Private key is my secret randomly genereted number that can create from itself public key. Reverse process is considered impossible :wink:
  2. a) Encryption - eg encrypting messages and allowing reciver to read it with shared senders public key through some kind of calculation.
    b) Unique signiture - eg to veryfi ownership of BTC adress via public key generated from private key
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#3293

  1. A public key is derived from a private key. However a private key canā€™t be derived from its public key.

  • A receiverā€™s public key can be used to encrypt a message that only the receiver could dercrypt with its private key.
  • Private keys are used to sign transactions, so that with that signature and the senderā€™s public key, the receiver can verify that a transaction was sent by the private key holder.
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#3294

Ahhā€¦ I see. So SHA256 is only for cryptocurrency encryption, not for the public/private keys? That is another function all together?

#3295

Yes. Hash functions like SHA256 are used to generate fingerprints of data and canā€™t be reversed, while PK cryptography is used to encrypt data that can be decrypted with the right private key for example. :slight_smile:

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#3296

Right. Makes senseā€¦ Thanks for your help!

#3297

  1. With the private key you sign messages, encrypt messages and decrypt messages, which comes to you. It is like your fingerprint, unique and just for you. Public key is the key, which everyone can see. To this public key can everyone send messages.

  2. Cryptocurrency and sending messages

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#3298

  1. Private keys are Public keys are used together to encrypt and decrypt information. The public key is generated from the private key. Example - When Alice and Bob want to communicate privately with one other, Alice gives her public key to Bob and Bob gives his public key to Alice. Then, Alice encrypts her message for Bob using Bobā€™s public key. Likewise, Bob encrypts his message for Alice using Aliceā€™s public key. Afterward, both Alice and Bob decrypt their respective messages using their private keys.

  2. Encryption and digital signatures.

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#3299
  1. Public key is derived from private key, which is large random number. Public key can be used only to encrypt messages and private key can decrypt messages.
  2. Public key cryptography can be used for encrypting data or for digital signatures.
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#3300

1.- Public and private key is a cryptography system which consists in a pair of related keys; the private, which is a random number and the public key that is derived from the first but calculation of the private key from the public key is not possible. The public key is the one that is shared and used to encrypt and the private key is only known by the owner and used for decryption.

2.- Digital signatures and encryption for secure communication.

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#3301
  1. Public and private keys can be used in tandem so that two individuals can share information across an open network without others being able to see the included information. Only the individual with the correct private key is able to de-code the information when it is received.
  2. Two uses for public key cryptography are sending covert and private messages, and sending and securing financial transactions.
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#3302
  1. the private key is a random number generated from your p.c and is yours and should be always kept secret and from your private key we can also generate a public key which can be shown to anyone as they cannot get your private key from your public key.
  2. The public key can be sent to others to send you crypto, you can use it for digital signatures and you can encrypt your messages and only the one with the private key can decrypt.
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#3303

1.Private key is my secret key,public is open for everyone.
2,encription &digital signatures.

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