Homework on Public and Private Keys - Questions

Blockchain and Bitcoin 101
#1451

Signatures are made using the private key so there can be only one valid sender :slight_smile:

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#1452

A private key is a random number generated by a wallet which is then in turn used to generate a public key. Without knowing the private key, there is no way to go “backwards” from a public key. Public keys are freely given while private keys are safeguarded so that no one else can impersonate someone else with it.

Public keys can be used for encrypting a message and also for digital signatures.

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#1453
  1. A private key is a long number randomly generated for the purpose of encryption, which is used to prove the right to access to a transation. Its maximum value may not exceed the maximum number of bits available for the type of encryption. The number must be kept confidential to prevent others from using it to access the transaction. The maximum value of a private key for the SHA-256 encryption is 2 ^ 256.
    A public key is a number derived from its corresponding private key by putting it through an elliptic curve function. The type of elliptic curve that is used in the bitcoin is secp256k1 which has the formula y^2 = x^3 +7. The starting coordinate used is G which is a constant. In order to derive a public key, elliptic curve multiplication must be performed private key times.
    The elliptic curve function is a trap-door function, meaning that it is infeasible to get the value of a private key knowing its corresponding public key. Nevertheless, the idea is that both public and private keys are mathematically linked, and it is the public key that is sent to the other side of a transaction, while the private key is kept confidential to be used for the creation of a signature in order to prove the right to a transaction. Therefore, any unlocking of a transaction does not involve sharing the same key.
  2. Public key cryptography is used for secure messaging and digital signatures.
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#1454

Homework: Public & Private Keys

  1. Private keys are random numbers generated by a specific mathematical formula that generate’s unique public keys are that only linked to your specific private key. Private keys are singular and only owned by you and should be kept secret, while public keys can be shared with the public, but no one can ever reverse engineer your public key to know your private key. It’s impossible.
  2. Public and private keys are used for encrypting messages / information and to sign transactions to verify the message and the sender.
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#1455
  1. First your computer generates a private key. On the basis of that private key applying some math formulas the public key is created.

Private key is the secret key that needs to be kept confidential. Public is seen by everybody that is acting as part of the network communication or a transaction of some sort. It is impossible to get to the private key knowing the public key (only one way directions is possible - to get to the public key knowing the private key). However, if private key is lost than there is no way to restore it and the transaction or access to the information is lost as well. If somebody gets the hold/steals the private key, this person gets the access to the information or a transaction.

  1. The two practical use of cryptography are a) Encryption of the data b) for digital signature.

The use of a digital signature is becoming crucial principle for Bitcoin transactions using a a BTC wallet. The same principal as described above are used to enable a Bitcoin transaction: 1) first the private key is generated, then on its basis the public key, and finally a Bitcoin address (that is used as yet another layer of security protection).

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#1456

  1. A public key is widely disseminated and allows others to send you securely encrypted messages and other information that you can decode with your closely held secret private key. A private key allows you to authenticate that you are the sender of any electronic transmission, the recipient verifies with your public key.

  2. Encryption and verification.

https://www.cs.uri.edu/cryptography/pgp.html

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#1457

  1. Private keys are randomly generated values that can be used to decrypt data that was encrypted from a public key that derived from the private key. However, a public key can never decrypt a private key.

  2. The two use-cases of public key cryptography are encryption and digital signatures. Digital signatures are more commonly used in blockchain technology.

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#1458

  1. A public key is used to encrypt data to share with another party. A randomly generated private key creates this public key and also receives information sent from another public key and decrypts it, as well as providing a unique signature to verify the transaction.

  2. Public key cryptography can be used for encryption and digital signatures.

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#1459
  1. Describe the concept of public and private key with your own words.
  2. What 2 use-cases can public key cryptography be used for?
  1. Having public key and private key on blockchain enables you to privately communicate with another person, and also to ensure the message is genuinely from the person you are communicating with.
  2. It can be used for A to send a message to B, and it can be used for B to check if the message is from A.
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#1460

  1. A private key is a large random number generated by a users computer, a public key is another number that is generated using the user’s private key. Together this pair is used to either encrypt messages/transactions or to digitally sign messages/transactions so that they can pass through the network and go to the recipient and the recipient uses this pair to either decrypt the message or verify the identity of the user who sent it.

  2. Public key cryptography can be used for Encryption or for Digital Signatures

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#1461
  1. Public key is accessible to everyone and it is used to encrypt a message a message that can only decrypted by private key.You can go from private key to public key but not vice versa.
    2.Sending a message and transactions.
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#1462

Public key cryptography is composed of two keys: a public key and a private key. Each key plays a role in encrypting and decrypting a message. The public key encrypts or transforms the data into a long string of alphanumeric characters and the private key decrypts or unscrambles that string into a legible message for the recipient. For example, to send a message to another person, I would need their public key. I would then encrypt the message with their public key and send it to them. When the recipient receives the message they can decrypt it with their private key. The recipient is able to decrypt the message because their public key is derived from their private key.

The two uses cases for public key cryptography are encryption and digital signatures. Encryption is used to transform data to make it uninterpretable and useless for unintended recipients. A digital signature is used to guarantee the authenticity of information.

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#1463

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

Your computer generates a large string of numbers which becomes your private key.
Based from these numbers a public key is generated. This public key is then used to generate your bitcoin address. The bitcoin address is normally used for day to day transaction but both the public key and the address can be broadcasted through the internet for everyone to see.
The public key and the address can only receive a transaction however it cannot spend.
The only authority to send or spend from these addresses is the private key.
Without the private key no one can take from this wallets.

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

a) Encryption- used to conceal information sent through the internet which could be decrypted using a private key.
b) Digital signatures- Used in digital key pairs known as wallets.

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#1464

1.a A private key is a personal random number that one should keep it safe and secret.

1.b A public key is a derrivated number taken from your private key, which it’s shown to everyone.

  1. It can be used for both Encryption, it’s useful but not used often with bitcoin, and Digital Signatures that provides identity integrity.
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#1465

+1 for knowing the function :smiley:

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#1466
  1. The concept of public and private keys is that the private key creates a public key which people can use to send encrypted messages and payments that can only be decrypted by the private key that created the public key.
  2. Use cases for public key cryptography, sending data and money.
#1467

It is also used for encryption and digital signatures, which is how money is sent on the blockchain :slight_smile:

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#1468

Thanks for the inputEmoji

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#1469
  1. Private key is just a random number. Analog to a email password.
    Public key is generated from the private key. If someone knows your public key then can send you an encrypted message and you can open it with your private key. Bitcoin address is generated from the public key. Bitcoin address is analog to an email address.
  2. Public key can be used for encrypting messages or the verify digital signatures.
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#1470

The private key is a random produced number which is used to generate the public key. In bitcoin, the private is key is used to send bitcoin and the public key is used to receive bitcoin.

Public key can be used for encryption to encrypt information and for digital signatures in bitcoin to identify transactions signed with private keys.

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