ruby 中的错误解密错误

在执行时cipher.final， 它说bad decrypt错误。我试图找出问题所在。但是，我找不到。你能告诉我我的代码有什么问题吗？

这是我的代码：

require 'openssl'
require 'base64'
require 'hex_string'

 result_h ="4fcd6b1ac843a2f8bf13f2e53dd5c1544fcd6b1ac843a2f8"
 key = result_h.to_byte_string

encrypt_str="79994A6EF73DA76C";
cipher = OpenSSL::Cipher.new("DES-EDE3-CBC")
cipher.decrypt
cipher.key = key
data = encrypt_str.to_byte_string
res = cipher.update( data )
res << cipher.final
result_h= res.unpack("H*")[0]
puts result_h.inspect;

错误是：

in `final': bad decrypt (OpenSSL::Cipher::CipherError)

我有类似的问题。在具体的例子中：

require 'openssl'
require 'base64'
require 'hex_string'

 result_h ="4fcd6b1ac843a2f8bf13f2e53dd5c1544fcd6b1ac843a2f8"
 key = result_h.to_byte_string

encrypt_str="79994A6EF73DA76C";
cipher = OpenSSL::Cipher.new("DES-EDE3-CBC")
cipher.decrypt
cipher.padding = 0
cipher.key = key
data = encrypt_str.to_byte_string
res = cipher.update( data )
res << cipher.final
result_h= res.unpack("H*")[0]
puts result_h.inspect;

=> "0befe932733d76e6"

如果添加 cipher.padding = 0 它会给你一个结果。