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Public key cryptography (aka asymmetric encryption) is a method of encrypting data using two keys:
1. Public key: known to two or more parties
2. Private key: known only to the owner

With an asymmetric key encryption anyone can encrypt messages using a known public key, but only the holder of the private key can decrypt it.

The basis of cryptography is the science of secure communications in the presence of untrusted parties. (R1) Public key cryptography provides non-repudiation of data communication and storage making its ‘use universal among-st Internet security protocols and standards.

Examples: It is widely used for HTTPS via TLS/SSL and for Bitcoin transactions and their wallets. In Bitcoin the sender generates a private key and public key. The sender signs the message and sends:

    1. the public key
    2. the signature and
    3. the message

These go to the network where the receiver checks that the message has been signed by the sender, which can only be done by the holder of the private key to the public key that is sent.

R2

References:
R1: https://en.wikipedia.org/wiki/Public-key_cryptography
R2: https://www.cryptocompare.com/wallets/guides/how-do-digital-signatures-in-bitcoin-work/
https://medium.com/@blairlmarshall/how-do-miners-validate-transactions-c01b05f36231

https://www.pluralsight.com/guides/the-cryptography-of-bitcoin

Pic: Photo by Marci Angeles on Unsplash

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