Class: RSA_AES_CBC

Inherits:
Object
  • Object
show all
Defined in:
lib/rsa_aes_cbc.rb

Overview

Simple hybrid crypto class using RSA for public key encryption and AES with CBC for bulk data encryption/decryption.

RSA is used to encrypt the AES primitives which are used to encrypt the plaintext.

@author: Tasos “Zapotek” Laskos

<tasos.laskos@gmail.com>
<zapotek@segfault.gr>

@version: 0.1

Instance Method Summary collapse

Constructor Details

#initialize(public_pem, private_pem = nil) ⇒ RSA_AES_CBC

If only encryption is required the private key parameter can be omitted.



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# File 'lib/rsa_aes_cbc.rb', line 47

def initialize(public_pem, private_pem = nil)
  @public_pem = public_pem
  @private_pem = private_pem
end

Instance Method Details

#decrypt(data) ⇒ String

Decrypts data.



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# File 'lib/rsa_aes_cbc.rb', line 92

def decrypt(data)
  rsa = OpenSSL::PKey::RSA.new(@private_pem)

  # decrypt with 256 bit AES with CBC
  aes = OpenSSL::Cipher.new('aes-256-cbc')
  aes.decrypt

  # unencode and unserialize to get the primitives and ciphertext
  primitives = YAML.load(Base64.decode64(data))

  aes.key = rsa.private_decrypt(primitives['key'])
  aes.iv  = rsa.private_decrypt(primitives['iv'])

  plaintext = aes.update(primitives['ciphertext'])
  plaintext << aes.final

  plaintext
end

#encrypt(data) ⇒ String

Encrypts data and returns a Base64 representation of the ciphertext and AES CBC primitives encrypted using the public key.



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# File 'lib/rsa_aes_cbc.rb', line 61

def encrypt(data)
  rsa = OpenSSL::PKey::RSA.new(@public_pem)

  # encrypt with 256 bit AES with CBC
  aes = OpenSSL::Cipher.new('aes-256-cbc')
  aes.encrypt

  # use random key and IV
  aes.key = key = aes.random_key
  aes.iv  = iv  = aes.random_iv

  # this will hold all primitives and ciphertext
  primitives = {}

  primitives['ciphertext'] = aes.update(data)
  primitives['ciphertext'] << aes.final

  primitives['key'] = rsa.public_encrypt(key)
  primitives['iv']  = rsa.public_encrypt(iv)

  # serialize everything and base64 encode it
  Base64.strict_encode64(primitives.to_yaml)
end