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diff --git a/jni/ruby/lib/securerandom.rb b/jni/ruby/lib/securerandom.rb
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+# -*- coding: us-ascii -*-
+begin
+  require 'openssl'
+rescue LoadError
+end
+
+# == Secure random number generator interface.
+#
+# This library is an interface for secure random number generator which is
+# suitable for generating session key in HTTP cookies, etc.
+#
+# You can use this library in your application by requiring it:
+#
+#   require 'securerandom'
+#
+# It supports following secure random number generators.
+#
+# * openssl
+# * /dev/urandom
+# * Win32
+#
+# === Examples
+#
+# Hexadecimal string.
+#
+#   require 'securerandom'
+#
+#   p SecureRandom.hex(10) #=> "52750b30ffbc7de3b362"
+#   p SecureRandom.hex(10) #=> "92b15d6c8dc4beb5f559"
+#   p SecureRandom.hex(13) #=> "39b290146bea6ce975c37cfc23"
+#
+# Base64 string.
+#
+#   p SecureRandom.base64(10) #=> "EcmTPZwWRAozdA=="
+#   p SecureRandom.base64(10) #=> "KO1nIU+p9DKxGg=="
+#   p SecureRandom.base64(12) #=> "7kJSM/MzBJI+75j8"
+#
+# Binary string.
+#
+#   p SecureRandom.random_bytes(10) #=> "\016\t{\370g\310pbr\301"
+#   p SecureRandom.random_bytes(10) #=> "\323U\030TO\234\357\020\a\337"
+module SecureRandom
+  if !defined?(OpenSSL::Random) && /mswin|mingw/ =~ RUBY_PLATFORM
+    require "fiddle/import"
+
+    module AdvApi32 # :nodoc:
+      extend Fiddle::Importer
+      dlload "advapi32"
+      extern "int CryptAcquireContext(void*, void*, void*, unsigned long, unsigned long)"
+      extern "int CryptGenRandom(void*, unsigned long, void*)"
+
+      def self.get_provider
+        hProvStr = " " * Fiddle::SIZEOF_VOIDP
+        prov_rsa_full = 1
+        crypt_verifycontext = 0xF0000000
+
+        if CryptAcquireContext(hProvStr, nil, nil, prov_rsa_full, crypt_verifycontext) == 0
+          raise SystemCallError, "CryptAcquireContext failed: #{lastWin32ErrorMessage}"
+        end
+        type = Fiddle::SIZEOF_VOIDP == Fiddle::SIZEOF_LONG_LONG ? 'q' : 'l'
+        hProv, = hProvStr.unpack(type)
+        hProv
+      end
+
+      def self.gen_random(n)
+        @hProv ||= get_provider
+        bytes = " ".force_encoding("ASCII-8BIT") * n
+        if CryptGenRandom(@hProv, bytes.size, bytes) == 0
+          raise SystemCallError, "CryptGenRandom failed: #{Kernel32.last_error_message}"
+        end
+        bytes
+      end
+    end
+
+    module Kernel32 # :nodoc:
+      extend Fiddle::Importer
+      dlload "kernel32"
+      extern "unsigned long GetLastError()"
+      extern "unsigned long FormatMessageA(unsigned long, void*, unsigned long, unsigned long, void*, unsigned long, void*)"
+
+      # Following code is based on David Garamond's GUID library for Ruby.
+      def self.last_error_message
+        format_message_ignore_inserts = 0x00000200
+        format_message_from_system    = 0x00001000
+
+        code = GetLastError()
+        msg = "\0" * 1024
+        len = FormatMessageA(format_message_ignore_inserts + format_message_from_system, 0, code, 0, msg, 1024, nil)
+        msg[0, len].force_encoding("filesystem").tr("\r", '').chomp
+      end
+    end
+  end
+
+  # SecureRandom.random_bytes generates a random binary string.
+  #
+  # The argument _n_ specifies the length of the result string.
+  #
+  # If _n_ is not specified or is nil, 16 is assumed.
+  # It may be larger in future.
+  #
+  # The result may contain any byte: "\x00" - "\xff".
+  #
+  #   p SecureRandom.random_bytes #=> "\xD8\\\xE0\xF4\r\xB2\xFC*WM\xFF\x83\x18\xF45\xB6"
+  #   p SecureRandom.random_bytes #=> "m\xDC\xFC/\a\x00Uf\xB2\xB2P\xBD\xFF6S\x97"
+  #
+  # If secure random number generator is not available,
+  # NotImplementedError is raised.
+  def self.random_bytes(n=nil)
+    n = n ? n.to_int : 16
+    gen_random(n)
+  end
+
+  if defined? OpenSSL::Random
+    def self.gen_random(n)
+      @pid = 0 unless defined?(@pid)
+      pid = $$
+      unless @pid == pid
+        now = Process.clock_gettime(Process::CLOCK_REALTIME, :nanosecond)
+        ary = [now, @pid, pid]
+        OpenSSL::Random.random_add(ary.join("").to_s, 0.0)
+        @pid = pid
+      end
+      return OpenSSL::Random.random_bytes(n)
+    end
+  elsif defined?(AdvApi32)
+    def self.gen_random(n)
+      return AdvApi32.gen_random(n)
+    end
+
+    def self.lastWin32ErrorMessage # :nodoc:
+      # for compatibility
+      return Kernel32.last_error_message
+    end
+  else
+    def self.gen_random(n)
+      flags = File::RDONLY
+      flags |= File::NONBLOCK if defined? File::NONBLOCK
+      flags |= File::NOCTTY if defined? File::NOCTTY
+      begin
+        File.open("/dev/urandom", flags) {|f|
+          unless f.stat.chardev?
+            break
+          end
+          ret = f.read(n)
+          unless ret.length == n
+            raise NotImplementedError, "Unexpected partial read from random device: only #{ret.length} for #{n} bytes"
+          end
+          return ret
+        }
+      rescue Errno::ENOENT
+      end
+
+      raise NotImplementedError, "No random device"
+    end
+  end
+
+  # SecureRandom.hex generates a random hexadecimal string.
+  #
+  # The argument _n_ specifies the length, in bytes, of the random number to be generated.
+  # The length of the resulting hexadecimal string is twice _n_.
+  #
+  # If _n_ is not specified or is nil, 16 is assumed.
+  # It may be larger in future.
+  #
+  # The result may contain 0-9 and a-f.
+  #
+  #   p SecureRandom.hex #=> "eb693ec8252cd630102fd0d0fb7c3485"
+  #   p SecureRandom.hex #=> "91dc3bfb4de5b11d029d376634589b61"
+  #
+  # If secure random number generator is not available,
+  # NotImplementedError is raised.
+  def self.hex(n=nil)
+    random_bytes(n).unpack("H*")[0]
+  end
+
+  # SecureRandom.base64 generates a random base64 string.
+  #
+  # The argument _n_ specifies the length, in bytes, of the random number
+  # to be generated. The length of the result string is about 4/3 of _n_.
+  #
+  # If _n_ is not specified or is nil, 16 is assumed.
+  # It may be larger in future.
+  #
+  # The result may contain A-Z, a-z, 0-9, "+", "/" and "=".
+  #
+  #   p SecureRandom.base64 #=> "/2BuBuLf3+WfSKyQbRcc/A=="
+  #   p SecureRandom.base64 #=> "6BbW0pxO0YENxn38HMUbcQ=="
+  #
+  # If secure random number generator is not available,
+  # NotImplementedError is raised.
+  #
+  # See RFC 3548 for the definition of base64.
+  def self.base64(n=nil)
+    [random_bytes(n)].pack("m*").delete("\n")
+  end
+
+  # SecureRandom.urlsafe_base64 generates a random URL-safe base64 string.
+  #
+  # The argument _n_ specifies the length, in bytes, of the random number
+  # to be generated. The length of the result string is about 4/3 of _n_.
+  #
+  # If _n_ is not specified or is nil, 16 is assumed.
+  # It may be larger in future.
+  #
+  # The boolean argument _padding_ specifies the padding.
+  # If it is false or nil, padding is not generated.
+  # Otherwise padding is generated.
+  # By default, padding is not generated because "=" may be used as a URL delimiter.
+  #
+  # The result may contain A-Z, a-z, 0-9, "-" and "_".
+  # "=" is also used if _padding_ is true.
+  #
+  #   p SecureRandom.urlsafe_base64 #=> "b4GOKm4pOYU_-BOXcrUGDg"
+  #   p SecureRandom.urlsafe_base64 #=> "UZLdOkzop70Ddx-IJR0ABg"
+  #
+  #   p SecureRandom.urlsafe_base64(nil, true) #=> "i0XQ-7gglIsHGV2_BNPrdQ=="
+  #   p SecureRandom.urlsafe_base64(nil, true) #=> "-M8rLhr7JEpJlqFGUMmOxg=="
+  #
+  # If secure random number generator is not available,
+  # NotImplementedError is raised.
+  #
+  # See RFC 3548 for the definition of URL-safe base64.
+  def self.urlsafe_base64(n=nil, padding=false)
+    s = [random_bytes(n)].pack("m*")
+    s.delete!("\n")
+    s.tr!("+/", "-_")
+    s.delete!("=") unless padding
+    s
+  end
+
+  # SecureRandom.random_number generates a random number.
+  #
+  # If a positive integer is given as _n_,
+  # SecureRandom.random_number returns an integer:
+  # 0 <= SecureRandom.random_number(n) < n.
+  #
+  #   p SecureRandom.random_number(100) #=> 15
+  #   p SecureRandom.random_number(100) #=> 88
+  #
+  # If 0 is given or an argument is not given,
+  # SecureRandom.random_number returns a float:
+  # 0.0 <= SecureRandom.random_number() < 1.0.
+  #
+  #   p SecureRandom.random_number #=> 0.596506046187744
+  #   p SecureRandom.random_number #=> 0.350621695741409
+  #
+  def self.random_number(n=0)
+    if 0 < n
+      if defined? OpenSSL::BN
+        OpenSSL::BN.rand_range(n).to_i
+      else
+        hex = n.to_s(16)
+        hex = '0' + hex if (hex.length & 1) == 1
+        bin = [hex].pack("H*")
+        mask = bin[0].ord
+        mask |= mask >> 1
+        mask |= mask >> 2
+        mask |= mask >> 4
+        begin
+          rnd = SecureRandom.random_bytes(bin.length)
+          rnd[0] = (rnd[0].ord & mask).chr
+        end until rnd < bin
+        rnd.unpack("H*")[0].hex
+      end
+    else
+      # assumption: Float::MANT_DIG <= 64
+      if defined? OpenSSL::BN
+        i64 = OpenSSL::BN.rand(64, -1).to_i
+      else
+        i64 = SecureRandom.random_bytes(8).unpack("Q")[0]
+      end
+      Math.ldexp(i64 >> (64-Float::MANT_DIG), -Float::MANT_DIG)
+    end
+  end
+
+  # SecureRandom.uuid generates a v4 random UUID (Universally Unique IDentifier).
+  #
+  #   p SecureRandom.uuid #=> "2d931510-d99f-494a-8c67-87feb05e1594"
+  #   p SecureRandom.uuid #=> "bad85eb9-0713-4da7-8d36-07a8e4b00eab"
+  #   p SecureRandom.uuid #=> "62936e70-1815-439b-bf89-8492855a7e6b"
+  #
+  # The version 4 UUID is purely random (except the version).
+  # It doesn't contain meaningful information such as MAC address, time, etc.
+  #
+  # See RFC 4122 for details of UUID.
+  #
+  def self.uuid
+    ary = self.random_bytes(16).unpack("NnnnnN")
+    ary[2] = (ary[2] & 0x0fff) | 0x4000
+    ary[3] = (ary[3] & 0x3fff) | 0x8000
+    "%08x-%04x-%04x-%04x-%04x%08x" % ary
+  end
+end