AES-256-CBC encryption/decryption w/o using JCE on JRuby

gistfile1.rb

# Java's JCE requires extra JVM config download named Jurisdiction Policy Files where AES keysize > 128bit.
# You can do encrypt/decrypt using BouncyCastle via JRuby's Java integration like this.
# Use this at your own risk.

require 'java'
require 'openssl'

java_import 'org.bouncycastle.crypto.BlockCipher'
java_import 'org.bouncycastle.crypto.engines.AESLightEngine'
java_import 'org.bouncycastle.crypto.modes.CBCBlockCipher'
java_import 'org.bouncycastle.crypto.params.KeyParameter'
java_import 'org.bouncycastle.crypto.params.ParametersWithIV'

bits = 256
message = "Hello World"

# encrypt w/o Jurisdiction policy files using BC.
cipher = CBCBlockCipher.new(AESLightEngine.new)
block_size = cipher.block_size
key = OpenSSL::Random.random_bytes(bits / 8)
iv = OpenSSL::Random.random_bytes(block_size)
param = ParametersWithIV.new(KeyParameter.new(key.to_java_bytes), iv.to_java_bytes)
cipher.init(true, param)

# bogus padding; do PKCS5 padding instead
len = message.bytesize
padded = (message + " " * (((len / block_size) + 1) * block_size - len)).to_java_bytes

buf = ("\0" * padded.length).to_java_bytes
0.upto(padded.length / block_size - 1) do |idx|
  pos = idx * block_size
  cipher.process_block(padded, pos, buf, pos)
end
cipher_text = String.from_java_bytes(buf)

# decrypt
cipher.init(false, param)
padded = cipher_text.to_java_bytes
buf = ("\0" * padded.length).to_java_bytes
0.upto(padded.length / block_size - 1) do |idx|
  pos = idx * block_size
  cipher.process_block(padded, pos, buf, pos)
end
plain_text_bc = String.from_java_bytes(buf)
p "decrypt by BC : " + plain_text_bc

# Following code needs Jurisdiction policy files.
cipher = OpenSSL::Cipher.new("AES-#{bits}-CBC")
cipher.decrypt
cipher.padding = 0
cipher.iv = iv
cipher.key = key
plain_text_jce = cipher.update(cipher_text) + cipher.final
p "decrypt by JCE: " + plain_text_jce

p plain_text_bc == plain_text_jce