Public Key Cryptography
This is much than other approaches and was first published in 1975As we have discussed this has key feature of only requiring one key per individual/organization requiring encrypted authenticated messaging
It has nontrivial infrastructure to distribute the N public keys for N organizations but this is better than N2 keys for secret key cryptography
Roughly the public key is a very large number that is the product of two primes. The private key is (related to) one of these primes.
It is used differently in two cases
- Transmission over insecure network where one encodes with public key of receiver (and receiver decodes with their private key)
- Authentication where you encode signature with private key and check the signature with public key