Homework on Public and Private Keys - Questions

Blockchain and Bitcoin 101
#1852

  1. Describe the concept of public and private key with your own words.
    At it’s heart public and private keys are just pairs of numbers from a random number generator, the public key being derived from the private. In the case of email the sender and the receiver both have a pair of keys that each party uses to either encrypt of decrypt their messages. The sender and receiver exchange public keys and encrypt each others respective messages with the opposite public key (sender encrypts with receivers and vice versa). The only way to decrypt the message is by having your own private key.

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

Public key cryptography can be used to encrypt and decrypt messages and to digitally sign messages.

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#1853

You can’t really receive messages you need a transfer medium to do that, but you can encrypt them to send them safely :wink: and you sigh transactions so you can send them.

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#1854

  1. Private key is a randomly generated number. This randomly generated number corresponds to a one-way public key.

  2. Encryption and Digital Signatures are the 2 use cases. Encryption uses the receivers public key with the senders secret message and encrypt it. Digital Signatures use the senders signature which is generated by the senders private key, and uses this with the public key in order to verify transactions.

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#1855

  1. A public key is derived from your private key which is kept secret. A public key and private key pair is automatically a bitcoin address. Your private key is randomly generated but impossible to trace.

  2. Encryption and digital signatures are the two use cases for public key cryptography. Digital signatures are used in BTC transactions.

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#1856
  1. Describe the concept of public and private key with your own words.
    A public key is your personal identity whereas your private key is the way to access what is stored within that public key address.
  2. What 2 use-cases can public key cryptography be used for?
    Public key cryptography can be used to verify that what was sent is correct as well as verify who you gave the consent to is the correct person or identity.
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#1857
  1. Describe the concept of public and private key with your own words.

Just like a padlock, a public key can be seen and attempted by any third party or spectator. The complex innerworkings of the padlock can be thought of as the encryption which match a private key with the unlocking mechanism being the digital signature. Anyone can see the padlock on the outside and know that there is a secret combination on the inside. Only the bearer of the key can know the unique grooves of the key, whereas the encryption makes up the notches or grooves of the key, or digital signature.

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

Public key cryptography can be used for both encryption and digital signatures. Encryption is useful any time you don’t mind a third party viewing a dataset or address while attaching a private value to the said address. This is especially valuable when thinking of Bitcoin or Blockchain when the Blockchain or distributed ledger is available for all to see. When encryption is coupled with the veracity of digital signatures, UTXO’s able to remain unique and private. We commonly think of Bitcoin as separate transactions when it is really, one large ledger made up of smaller blocks. As it relates to public keys or public addresses, anyone can view the transaction(s) but only those with the private key can de-crypt or deride the message. The message is made up of information such as input + output data including UTXO’s. Digital signatures are very complex hashes by the private key to sign a message. When a TX is sent, it is “signed” or appended with the digital signature.

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#1858
  1. A public key is the address for receiving funds and can be shared publicly. The private key is the signature to verify payments from that public key. The public key is the hash of the initial private key.
  2. Two key public key cryptography applications are message encryption and on chain traceability.
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#1859

  1. A private key is a random number that is known only by it’s owner. The public key is generated from the private key and is known by everyone who wants to communicate with the owner of the private key.

  2. There a 2 use cases for public/private key cryptography.
    Case #1 (encrypt a message): The public key is used to encrypt messages by the public and only the owner of the matching private key can decrypt the message.
    Case #2 (sign a message): The private key is used to sign a message and anyone using the public key can verify that the message was signed by the owner of the private key.

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#1860
  1. Describe the concept of public and private key with your own words.

public key is accessible to everyone private key only me. when i send a message i will encrypt with private key and public key

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

digital signatures
encryption

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#1861

Public and Private keys are used to encrypt data so that it may be sent back and forth between two parties to very specific addresses without anyone being able to intercept it.
The two use cases of public key cryptography are:
1.) Public key encryption: using someone’s public key to encrypt your data and send to them privately.
2.) Digital Signatures: a derivation of one’s private key, using this and a person’s public key allows you to verify that whatever was sent actually came from the person who digitally signed it.

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#1862

Technically nowadays the bitcoin address is a hash of the public key, historically this was not the case and public keys were used as the address, but was later changed to reduce the size of transactions :slight_smile:

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#1863

These are actually both examples of digital signatures, the second use case would be encryption :slight_smile:

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#1864

Encryption is not used on the Bitcoin blockchain. Everything is public for everyone to see. We use digital signatures to sign transactions to unlock the funds, but the locked funds can be seen by anyone :slight_smile:

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#1865

What do you mean by that? One can view the addresses without signing them, so you use the signature only for sending really :slight_smile:

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#1866

a private key in cryptocurrencies is build out of an seedphrase and you need it to unlock the wallet which is locked with the public key

#1867

The seedphrase is just a set of predetermined words that can be used to easily remember the private key and this “master key” is then used to derive multiple private keys from it. This is described in bit 32 and is also called a hierarchical deterministic wallet (or HD Wallet). From these set of keys you can derive public keys, but you can never get the private key from the public key, that would break security :slight_smile:

Do you know how these keys can be used for?

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#1868
  1. Private key is a random number generated by a computer to encrypt the message. Then the public key can be derived from the private key and shared publicly. The public key is linked to the private key of the owner of private key, but it is not possible to recognize your private key using public key available to public’s view.
  2. We use public key to encrypt the message (e-mail) or for digital signature (to sign BTC transaction that we spend)
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#1869

Public key is a random string that can be viewed by the public without risking your privatekey, also your bitcoin adress is derived from the public key.
Private key is the random string that you need to have to be able to authorize transactions from your public key.

  1. sending and receiving transaction
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#1870

Private key is the key that is used as a signature for transactions as well as to decrypt what is sent to the public key. The public key is the face of a bitcoin wallet, something can be sent but cannot be taken from it. Key’s themselves exist to decrypt and encrypt messages or transactions.

Encryption and as a digital signature.

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#1871

  1. Private key are actually a set of random numbers. Public key are generated from private key. There is no way to derive your private key from Public key.

  2. message encryption and transaction signing.
    Msg encryption is done when you encrypt with public key of receiver. Receiver decrypts it with his private key.
    Transaction signing is done by sender encrypt with his private key. Receiver decrypt with senders public key.

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