in public key cryptography there should be two key called private key and public key

private key kept in secret and public key put in public

in public key cryptography the its should be easy to encrypt and decrypt the files using keys

either of these keys can used to encrypt the file and other key can be used to decrypt the file

generation of these keys should be easy

it should be unfeasible to decrypt the cipher text using same key which is used to encrypt the file .

by knowing the public key the opponent cant determine the private key and it should be unfeasible

but computing power needed for public key cryptography is higher than private key cryptography