explodes.rb

require 'openssl'
require 'rubygems'
require 'mechanize'

agent = WWW::Mechanize.new()
page = agent.get(:url => "https://www.gmail.com")

#use OpenSSL between mechanize requests.
public_key = OpenSSL::PKey::RSA.new(File.read(File.dirname(__FILE__) + "/mykeypublic.pem"))
private_key = OpenSSL::PKey::RSA.new(File.read(File.dirname(__FILE__) + "/mykey.pem"))
data = "hello world"
puts "Data Before Encryption: #{data}"
encrypted_data = public_key.public_encrypt(data)
dencrypted_data = private_key.private_decrypt(encrypted_data)
puts "Data After Decryption: #{dencrypted_data}"

response = agent.submit(page.forms.first)
#will raise: OpenSSL::SSL::SSLError: SSL_read:: no start line

mykey.pem

-----BEGIN RSA PRIVATE KEY-----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-----END RSA PRIVATE KEY-----

mykeypublic.pem

-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDBLXT5EwIrLvdyTGc3hcjAFj7y
BngLarwwm6jtWLHtEXm1ehKVnd4rNUF6Et1kFbk4h4fOsj2vS0bpcGDGPg8X120w
/nAsx+MWB069vHi4qHhQ27MoWSqti4xd0QNxl5TerlGo8IlibikXdaGykhElocWB
/NL1HjL8z+ww1YkyewIDAQAB
-----END PUBLIC KEY-----

works_fine.rb

require 'openssl'
require 'rubygems'
require 'mechanize'

agent = WWW::Mechanize.new()
page = agent.get(:url => "https://www.gmail.com")
response = agent.submit(page.forms.first)