Homework on Public and Private Keys - Questions

Blockchain and Bitcoin 101
#243

  1. Describe the concept of public and private key with your own words.
    They work together. The public key is derived from the private key, but cannot be reversed. This enables privacy & security in transfering data.

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

#244
  1. Describe the concept of public and private key with your own words.

Private and public keys are used to safe guard sharing of private information on a public network via cryptographic encryption. A private key is a randomly generated large number that once hashed forms the public key. This process is unidirectional that prevents a random private key from being compromised via the publicly key. This creates a secure way to sign, send, and decrypt information contained within the encryption.

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

Public keys can be used to both encrypt private messages and digitally sign transactions.

:slight_smile:

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#245

Describe the concept of public and private key with your own words:
The private key is generated by a random number and from that a public key is generated. The public key is used to encrypt sensitive information. And the private key is used to decrypt information that is encrypted by the public key, or to sign transactions with bitcoin for example.

What 2 use-cases can public key cryptography be used for?
Sending information and transferring funds.

#246

  1. Describe the concept of public and private key with your own words.
    A private key is a randomly generated string. This is only known to you. From this private key a public key is generated to use to encrypt the data exchanged between users.

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

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#247
  1. A public key is derived from a private key but cannot be reversed.
  2. Encryption and digital signatures
#248

1.the puclic key is for the world to use to send massage bitcoin whatever you want keep secret from snooping eyes and the private key is the value to one self in terms ofsending reciving bitcoin for ex
2.it can be used for encrypting a simpel massage aswell as you can generate your bitcoin addres from it

#249

Homework on Public and Private Keys - Questions

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

The private key is generated by the computer/wallet of the receiver. The private key on his turn will generate the public key that is accessible to everyone. If the sender wants to send a message to the receiver he will use the public key of the receiver to encrypt the message. Only with the private key of the receiver the message can be decrypted.

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

Encryption and digital signatures

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#250

1- A public key is derived from a private key and is made available for everyone so see and use if they want to send me an encrypted message. I still don’t see/understand how they combine their message and the public key to actually encrypt the message. I also don’t understand how the decrypting works and how the message is extracted (since it needs to be decoupled from the the public key when it arrives)

2- Cryptography and Digital signature

#251
  1. Encryption: Private key is generated privately by the receiver. This key is used to generate a public key which the sender uses to encrypt the message. The receiver then uses their private key to decrypt this message.
    Digital signatures: The sender digitally signs a message with their private key. The receiver then uses this signature to verify the identity of the sender by comparing it to the sender’s public key.
  2. Encrypting and digital sign.
#252

Your unique private keys are used to generate public keys which can be used on an open source network without anyone obtaining your private key and gaining access to your assets.

Public key cryptography is used for encryption and for digital signatures.

#253
  1. Private key only known to myself. Public key derived from private key and known to all. Message encrypted with public key can be decrypted with private key only. Encrypted message that can be decrypted with public key, could only have been decrypted with my private key.
  2. Encrypting a message intended only for the holder of the private key. Signing a message with private key, which verifies with public key that it could only have been encrypted by the holder of the private key.
#254

  1. Public and private keys work in pairs.
    A public key is generated from the private key. Private key is your private signature that only you should know, as opposite to a public key which can be shared with others. Noone can find your private key (input) from your public key (output).

  2. a) For encrypting and

b) to digitaly sign messages so the receiving party can be 100% sure that you were the sender of the msg.

#255

A public key is the btc address that receives money.
A private key is the nonce or random integer generated by my computer that is a unique signature and unseen by anyone else ever as long as I keep it private that enables me to send and receive btc. Digital signatures and encryption are two use cases for public key cryptography.

#256
  1. Public is for the world to see and Private is shhh.
    2.signature from recipient and generated by private keys.
#257
  1. A private key is only for you to see and a public key can be made public. Your computer will generate a random private key and from that you can create a public key.
  2. Encryption and Digital signature. For encryption it can be for sending an encrypted message across a open network so only the person intended to receive the message can decrypt it and know what it says. Digital signature is so the person can verify who sent the message. This is used for bitcoin. Your digital signature is signed by your private key so everyone knows you sent the bitcoin. If you lose your private key you lose your coins. If someone steals your private key, they steal your coins.
#258
  1. To use Bitcoin via the blockchain for transactions, you need an address to receive and send. But this unique address should be kept private - think of it as a special receiving account PIN number, being much longer at 64 characters. In order to share this address safely, a public version of it is created. This public key is derived from the private key. It is, however, created using a different form of encryption, and is therefore not as secure. A new public key should be created each time you spend bitcoin, as information could be derived from the public key once it has been used.
  • From Wikipedia
    :black_small_square: In Bitcoin, a private key is a 256-bit number, which can be represented one of several ways. Here is a private key in hexadecimal - 256 bits in hexadecimal is 32 bytes, or 64 characters in the range 0-9 or A-F.

E9873D79C6D87DC0FB6A5778633389_SAMPLE_PRIVATE_KEY_DO_NOT_IMPORT_F4453213303DA61F20BD67FC233AA33262

secp256k1 refers to the parameters of the elliptic curve used in Bitcoin’s public-key cryptography, and is defined in Standards for Efficient Cryptography (SEC)
https://en.bitcoin.it/wiki/Secp256k1

  1. The level of probability to duplicate or guess a 64 character private key is such that the ‘universe will collapse’ before that happens. ‘Public Key’ secp256k1 cryptography is used: to send or receive by generating a Bitcoin address as a safely shareable key, thus keeping the actual sensitive key private as well as allowing verification - ability to sign via this digital signature.
#259

Bitcoin addresses are not the same as public keys. A bitcoin address is derived from the public key with some algorithm. (double hashed and some additional steps and information like version number and checksum)

#260

Thank you for noticing the mistake and correcting. Wondering why it must be a derivative and what the purpose of the double hash and version number are?

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#261

That’s for adittional security reasons. For example if quantum computers can break ECDSA, they still need to break Sha256 to ‘hack’ you. But when you spend your bitcoins, you do reveil your public key. That’s also a reason why you never should reuse the same address.
Version numbers are for knowing wich way you gonna lock the coins to an address. today on the bitcoin mainnet we have addresses starting with 1, 3 or bc1
checksum is to throw an error if you mistyped 1 character or something.

#262

A public key is a random number generated using a secret private key that has also been randomly generated. A public key can be known the world as you can never derive the public key from the private key. The private key is used to decrypt a set of data that has been encrypted by a private key.

Public key cryptography can be used as encryption to open a message or it can be used as a digital signature signed by the private key to verify a sender