Cryptography to the Rescue (cont.)

Public-key cryptography for signatures and spontaneous secure exchanges

: Each user has a keypair: a "public" key and a "private" key
Data encrypted with one key can only be decrypted with the other
It is "computationally infeasible" to deduce the Private Key from the Public Key
Encryption and decryption slower than symmetric cryptography
Most popular public-key system: RSA

: Anton encrypts a document using Beatrice's (well-known) Public Key
Beatrice uses her Private Key to decrypt the document
This works, assuming that only Beatrice knows the Private Key

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