# How do I do public-key encryption with `openssl`

?

OpenSSL is a public-key crypto library (plus some other random stuff). Here’s how to do the basics: key generation, encryption and decryption. We’ll use RSA keys, which means the relevant `openssl`

commands are `genrsa`

, `rsa`

, and `rsautl`

.

```
# Alice generates her private key `priv_key.pem`
openssl genrsa -out priv_key.pem 2048
# Alice extracts the public key `pub_key.pem` and sends it to Bob
openssl rsa -pubout -in priv_key.pem -out pub_key.pem
# Bob encrypts a message and sends `encrypted_with_pub_key` to Alice
openssl rsautl -encrypt -in cleartext -out encrypted_with_pub_key -inkey pub_key.pem -pubin
# Alice decrypts Bob's message
openssl rsautl -decrypt -in encrypted_with_pub_key -inkey priv_key.pem
```

Tagged . All content copyright James Fisher 2017. This post is not associated with my employer.