Raspberry Pi using letsencrypt:

`gpg --recv-key 7638D0442B90D010`
`gpg --recv-keys 8B48AD6246925553`
`gpg -a --export 7638D0442B90D010 | sudo apt-key add -`
`gpg -a --export 8B48AD6246925553 | sudo apt-key add -`

`git clone https://github.com/letsencrypt/letsencrypt`

`cd letsencrypt`

`time ./letsencrypt-auto`