Linux openssl

Description

The way public/private keys work, is a public key is used to encrypt data and only a private key is capable of decrypting it.

Public Key -> Encrypt.

Private Key -> Decrypt.

Example

This is a real example of public private key.

Create a public & private key.

Create a private key.

 openssl genrsa -out mykey.pem 1024

Create a public key.

 openssl rsa -in key.pem -pubout -out pubkey.pem

or

 openssl rsa -in mykey.pem -pubout > mykey.pub

This will calculate the public key from the private key.

Encrypt a file with a public key

 cat plain.txt | openssl rsautl -encrypt -pubin -inkey ./is_rsa.pub.pem > cipher.txt

Decrypt a file with a private key

 cat cipher.txt | openssl rsautl -decrypt -inkey ~/id_rsa.private.pem