Question

我们要解密AES-128加密的m3u8 TS文件。这是我们的.m3u8文件

#EXTM3U
#EXT-X-TARGETDURATION:12
#EXT-X-ALLOW-CACHE:YES
#EXT-X-PLAYLIST-TYPE:VOD
#EXT-X-KEY:METHOD=AES-128,URI="enc.key?wmsAuthSign=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ0b2tlbiI6IjdjY2I5ZTAxZGI1YzVkM2IzMWUzMzc1NzQ3MjZjNjYwIiwiZXhwIjoxNTEzMTU4ODM5LCJpc3MiOiJTYWJhIElkZWEgR1NJRyJ9.vvYKPY9tyBnhGGnNtY-XLy_Hz5cyJx5Ma2APVv0g5dk"
#EXT-X-VERSION:3
#EXT-X-MEDIA-SEQUENCE:1
#EXTINF:6.000,
s-1-v1-a1.ts?wmsAuthSign=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ0b2tlbiI6IjdjY2I5ZTAxZGI1YzVkM2IzMWUzMzc1NzQ3MjZjNjYwIiwiZXhwIjoxNTEzMTU4ODM5LCJpc3MiOiJTYWJhIElkZWEgR1NJRyJ9.vvYKPY9tyBnhGGnNtY-XLy_Hz5cyJx5Ma2APVv0g5dk
#EXTINF:6.000,
s-2-v1-a1.ts?wmsAuthSign=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ0b2tlbiI6IjdjY2I5ZTAxZGI1YzVkM2IzMWUzMzc1NzQ3MjZjNjYwIiwiZXhwIjoxNTEzMTU4ODM5LCJpc3MiOiJTYWJhIElkZWEgR1NJRyJ9.vvYKPY9tyBnhGGnNtY-XLy_Hz5cyJx5Ma2APVv0g5dk
#EXTINF:6.000,
s-3-v1-a1.ts?wmsAuthSign=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ0b2tlbiI6IjdjY2I5ZTAxZGI1YzVkM2IzMWUzMzc1NzQ3MjZjNjYwIiwiZXhwIjoxNTEzMTU4ODM5LCJpc3MiOiJTYWJhIElkZWEgR1NJRyJ9.vvYKPY9tyBnhGGnNtY-XLy_Hz5cyJx5Ma2APVv0g5dk
#EXTINF:12.000,
s-4-v1-a1.ts?wmsAuthSign=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ0b2tlbiI6IjdjY2I5ZTAxZGI1YzVkM2IzMWUzMzc1NzQ3MjZjNjYwIiwiZXhwIjoxNTEzMTU4ODM5LCJpc3MiOiJTYWJhIElkZWEgR1NJRyJ9.vvYKPY9tyBnhGGnNtY-XLy_Hz5cyJx5Ma2APVv0g5dk

我们有enc.key个文件和'enc.key' DVQpuWrxZLd2nCTTxAysIg==的服务器响应

我们正在使用这些C＃函数进行解密，但我们不知道如何查找salt或块大小？或者基本上我们是以正确的方式做到的？

 public static void  DecryptFile(string inputFile, string output,string password)
        {

            byte[] bytesToBeDecrypted = File.ReadAllBytes(inputFile);
            byte[] passwordBytes = Encoding.UTF8.GetBytes(password);
            passwordBytes = SHA256.Create().ComputeHash(passwordBytes);
            byte[] bytesDecrypted = AES_Decrypt(bytesToBeDecrypted, passwordBytes);


            File.Delete(inputFile);


            File.WriteAllBytes(output, bytesDecrypted);
        }


        public static byte[] AES_Decrypt(byte[] bytesToBeDecrypted, byte[] passwordBytes)
        {
            byte[] decryptedBytes = null;

            // Set your salt here, change it to meet your flavor:
            // The salt bytes must be at least 8 bytes.
            byte[] saltBytes = new byte[] { 1, 2, 3, 4, 5, 6, 7, 8 };

            using (MemoryStream ms = new MemoryStream())
            {
                using (RijndaelManaged AES = new RijndaelManaged())
                {
                    AES.KeySize = 128;
                    AES.BlockSize = 128;

                    var key = new Rfc2898DeriveBytes(passwordBytes, saltBytes, 1000);
                    AES.Key = key.GetBytes(AES.KeySize / 8);
                    AES.IV = key.GetBytes(AES.BlockSize / 8);

                    AES.Mode = CipherMode.CBC;
                    AES.Padding = PaddingMode.PKCS7;
                    using (var cs = new CryptoStream(ms, AES.CreateDecryptor(), CryptoStreamMode.Write))
                    {
                        cs.Write(bytesToBeDecrypted, 0, bytesToBeDecrypted.Length);
                        cs.Close();
                    }
                    decryptedBytes = ms.ToArray();
                }
            }

            return decryptedBytes;
        }

Answer 1

这里已经存在类似的问题（无法找回）

如何找到盐或块大小

查看您的EXT-X-KEY标题。它指出AES-128，因此您必须使用AES-128（它的密钥大小，块大小始终为128位）。

根据RFC默认情况下，使用带有Pkcs7填充的CBC模式。

4.3.2.4. EXT-X-KEY部分进一步指出：the Initialization Vector (IV) attribute value or the Media Sequence Number as the IV

所以IV应该出现在EXT-X-KEY标题中。如果没有，则使用序列号（这对于CBC来说是个糟糕的想法，但事实就是如此）。

或基本上我们正在以正确的方式进行

基本上它看起来不错（盐和钥匙除外）。我不确定加密密钥是什么。来自服务器的编码响应有16个比特（128比特），所以我认为这可能是关键（你必须自己找出）

如何解密AES-128加密的m3u8 TS文件

1 个答案: