问题描述
在试图建立一个可互操作的加密系统，我光时认识的一个奇怪的局面：证明的概念。
While trying to setup an interoperable encryption system, I met a weird situation during a light "proof-of-concept".
我写了下面code在Ruby中：
I wrote the following code in Ruby to:
- 我的文件系统上创建一个从虚拟文本文件的加密文件
- 解密加密文件
- 与原始文件进行比较，并检查它们是否相同
下面是code：
require 'openssl'
require 'base64'
# Read the dummy file
data = File.read("test.txt")
# Create an encrypter
cipher = OpenSSL::Cipher::AES.new(256, :CBC)
cipher.encrypt
key = "somethingreallyreallycomplicated"
cipher.key = key
# Encrypt and save to a file
encrypted = cipher.update(data) + cipher.final
open "encrypted.txt", "w" do |io| io.write Base64.encode64(encrypted) end
# Create a decrypter
decipher = OpenSSL::Cipher::AES.new(256, :CBC)
decipher.decrypt
decipher.key = key
# Decrypt and save to a file
encrypted_data = Base64.decode64(File.read("encrypted.txt"))
plain = decipher.update(encrypted_data) + decipher.final
open "decrypted.txt", "w" do |io| io.write plain end
# Compare original message and decrypted message
puts data == plain #=> true
一切正常，这个脚本输出真
Everything works fine, this script outputs "true"
然后我试图使用OpenSSL命令行解密文件我用下面的命令：
Then I tried to use the openssl command-line to decrypt my file with the following command:
openssl aes-256-cbc -d -a -in encrypted.txt -k somethingreallyreallycomplicated
但我得到：坏的幻数
为什么？
推荐答案
您需要使用 -K （大写）和 -IV在命令行上选项来指定密钥和IV明确为十六进制数字的字符串。如果你使用 -k （小写），OpenSSL的派生将使用一个密钥导出函数的口令密钥和IV。当OpenSSL的派生一个键，它也将使用一个咸鱼密文格式，它是与你所期望的普通列块CBC是不相容的。
You need to use the -K (upper case) and -iv options on the command line to specify key and IV explicitly as a string of hex digits. If you use -k (lower case), OpenSSL will derive key and IV from the password using a key derivation function. When OpenSSL derives a key, it will also use a "salted" ciphertext format which is incompatible with the plain blockwise CBC you are expecting.
请注意，在你的Ruby code，您使用的是ASCII字符串的第一个256位（32字节）直接作为重点，这是几乎可以肯定不是你想要的一个现实世界的应用程序，其中安全性是一个问题。你应该用一个（随机生成）的二进制键，或从派生密码的密钥使用密钥导出函数，如 ，或 scrypt
Note that in your Ruby code, you are using the first 256 bits (32 bytes) of an ASCII string directly as a key, which is almost certainly not what you want for a real world application where security is an issue. You should use a (randomly generated) binary key, or derive a key from a password using a key derivation function such as PBKDF2, bcrypt or scrypt.
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