Edit the secret message in encrypt.rb, run it, tell me what it prints

1.generate.rb

# I used this to generate the public / private keypair and sign them
require 'base64'
require 'openssl'

private_key = OpenSSL::PKey::RSA.generate 1024
public_key  = private_key.public_key
signature   = private_key.sign
  OpenSSL::Digest::SHA256.new,
  public_key.to_pem
)

File.write 'josh.sig',  Base64.strict_encode64(signature)
File.write 'josh.pub',  public_key.to_pem
File.write 'josh.priv', private_key.to_pem

2.encrypt.rb

# The only thing you need to edit is what's in this heredoc:
secret_message = <<SECRET
write your
secret message
in here
SECRET

# These are in the standard library, you shouldn't need to install anything
require 'openssl'
require 'base64'

# Verify my public key: I signed it with my private key
josh_pub_key = OpenSSL::PKey.read <<PEM
-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDOI0DWR7hdRlho4lNu5ymHOVzw
M1uHGHmfEpt2N6givU2ty0j1+/NYYLGf6pSi3KwBSBShqPe4mZ5DFByzCl3K5kDx
eDmKN9B8qGjzftbo+IMSimNGyP6POdvpr9p+1lBsWCSzX5joxSrmSkKVHhMWXMVd
ogG5vFyuRmTfqlegKQIDAQAB
-----END PUBLIC KEY-----
PEM

josh_sig = Base64.strict_decode64 'Yga8FwuplMTskFEJrFOMeOegVikBIbMdySq0VXsnmB2wjOxG2YI8+pzeibOLmvdU3j8GVpUJZSkfkKeCR7GYO0X14MCVt175qr7Is8L/+qlg/qbRjo0rXup0sUOcM/ohgb9L5Yk9FrWY24uavkplL7ceuC8hQoEBtUIFGYIVz40='
verified = josh_pub_key.verify(
  OpenSSL::Digest::SHA256.new,
  josh_sig,
  josh_pub_key.to_pem
)
unless verified
  $stderr.puts 'Invalid signature, DO NOT TRUST!'
  exit 1
end

# Generate a Cipher to encrypt the data
cipher = OpenSSL::Cipher::AES.new(256, :CBC)
cipher.encrypt
key = cipher.random_key
iv  = cipher.random_iv

# encrypt / encode / print all the data
puts Base64.strict_encode64(josh_pub_key.public_encrypt(key))
puts
puts Base64.strict_encode64(josh_pub_key.public_encrypt(iv))
puts
puts Base64.encode64 cipher.update(secret_message) + cipher.final

3.decrypt.rb

encrypted_key = "FIXME"
encrypted_iv  = "FIXME"
encrypted_msg = <<MSG
FIXME
MSG

require 'openssl'
require 'base64'
josh_priv_key = OpenSSL::PKey.read File.read 'josh.priv'
decipher = OpenSSL::Cipher::AES.new(256, :CBC)
decipher.decrypt
decipher.key = key = josh_priv_key.private_decrypt Base64.strict_decode64 encrypted_key
decipher.iv  = iv  = josh_priv_key.private_decrypt Base64.strict_decode64 encrypted_iv
puts decipher.update(Base64.decode64 encrypted_msg) + decipher.final