AES - symmetric algorithms for encryption and decryption

AES-256-CBC-sample.rb

require 'openssl'
require 'digest/sha2'

# Config
alg = "AES-256-CBC"

# Key
key = OpenSSL::Cipher::Cipher.new(alg).random_key

# Init Digest
digest = Digest::SHA256.new
digest.update(key)
# initialization vector is not used, because key is random
# iv = OpenSSL::Cipher::Cipher.new(alg).random_iv
# digest.update(iv)

# key64 = [key].pack('m')  # Base64 and store the key
# key64.unpack('m')[0]     # retrieve key from Base64
# raise 'Key Error' if(key.nil? or key.size != 32)

# Init encryption Cipher
aes = OpenSSL::Cipher::Cipher.new(alg)
aes.encrypt
aes.key = key
# aes.iv = iv  # iv is not used

# Encode plain text.
cipher = aes.update <<PLAIN
  Classified!!
  This is a list of all my private data:
    Item 1
    Item 2
    Item 3
    Item 4
    ...
PLAIN
cipher << aes.final

# Transmit or store Base64 cipher text
cipher64 = [cipher].pack('m')

##################################################################

# cipher64 and key retrieved
# Init decryption Cipher
decode_cipher = OpenSSL::Cipher::Cipher.new(alg)
decode_cipher.decrypt
decode_cipher.key = key
# decode_cipher.iv = iv  # iv is not used

# Decode cipher text
plain = decode_cipher.update(cipher64.unpack('m')[0])
plain << decode_cipher.final