├── README.md ├── ddlcpcydec.php └── LICENSE /README.md: -------------------------------------------------------------------------------- 1 | # DDLC Plus Asset Decrypter 2 | ![Version: 1.1](https://img.shields.io/badge/Version-1.1-brightgreen?style=for-the-badge) 3 | 4 | Doki Doki Literature Club Plus Asset Decrypter 5 | 6 | Used to decrypt encrypted Streaming Asset Bundle files (*.cy) in DDLC-Plus. 7 | 8 | ## How to use 9 | 1. Download and install PHP for your system from the [official website](https://www.php.net/downloads). 10 | 2. Open the terminal and use PHP interpreter to execute the [script](ddlcpcydec.php) with the usage. 11 | 3. Wait for the script to run. 12 | 4. Use [Perfare/AssetStudio](https://github.com/Perfare/AssetStudio/) or other tools to unpack the decrypted asset file. 13 | 14 | ## Changelog 15 | - v1.1: 16 | - Split file into 10M cache to speed up the decryption process 17 | - v1.0: 18 | - First ver 19 | 20 | ## TO-DOs 21 | - v1.3: 22 | - Use multiple threads to speed up the decryption process (Requires pthread extension) 23 | - v1.2: 24 | - Iterate through paths to decrypt all files 25 | 26 | ## Workaround 27 | The game has been cleared and I want to get its wallpaper and new music. 28 | 29 | When I got the file, I found that its header is the same, but in an unknown format. By consulting the C# code, the game calls the regular AssetBundles load method. Nothing related to decryption was found in the C# code. I started to disassemble the native PE program and also found no code for decryption. 30 | 31 | So I seemed to be stuck in a conundrum. I started to guess the encryption method, and the common ones are AES and XOR. But I didn't find any AES decryption method needed, so I ruled it out. Then I turned to XOR, starting by first guessing the key in a loop from 0 to 100. 32 | 33 | Fortunately, the UnityFS file header and the Unity3D engine version were successfully decrypted when the XOR key was 40. By comparing it with StreamingAssets from other Unity3D powered games, I was convinced that this was the normally file. 34 | 35 | Unpacked it using AssetStudio, everything worked fine and I got the wallpaper and music I wanted. 36 | 37 | There is a saying in Chinese called "暴力出奇迹". Great discoveries require bold guesses, and often they work. :) 38 | 39 | ## Why do I use PHP 40 | Simply, I hate Python syntax. 41 | 42 | As an interpretive language, PHP has a friendly syntax similar to that of other languages and is easy to use. 43 | 44 | In addition, ~~PHP is the best language in the world and does not accept any refutation~~. LMAO 45 | 46 | ## License 47 | The project is open source under [Apache License v2.0](LICENSE). All rights reserved for script author [MlgmXyysd](https://github.com/MlgmXyysd/). 48 | -------------------------------------------------------------------------------- /ddlcpcydec.php: -------------------------------------------------------------------------------- 1 | = 2) { 48 | $argument_file_in = $argv[1]; 49 | if (substr($argument_file_in, -3) !== ".cy") { 50 | exit("! \033[31mOnly supports files with .cy extension.\033[0m\n"); 51 | } 52 | if ($argc >= 3) { 53 | $argument_file_out = $argv[2]; 54 | } else { 55 | $argument_file_out = substr($argument_file_in, 0, -2) . "assets"; 56 | } 57 | } else { 58 | exit("- \033[33mUsage: ddlcpcydec.php [output file]\033[0m\n"); 59 | } 60 | 61 | /** 62 | * XOR for string 63 | * 64 | * @access public 65 | * @param string $str String to be processed 66 | * @param int $key XOR Key 67 | * @return string Processed string 68 | */ 69 | function xor_string($str, $key = 40) { 70 | $result = ""; 71 | for ($i = 0; $i < strlen($str); $i++) { 72 | $result .= chr(ord($str[$i]) ^ $key); 73 | } 74 | return $result; 75 | } 76 | 77 | $file_in = fopen($argument_file_in, "r") or exit("! \033[31mUnable to open in file!\033[0m\n"); 78 | $file_out = fopen($argument_file_out, "a") or exit("! \033[31mUnable to open out file!\033[0m\n"); 79 | 80 | print("- Loading encrypted file " . $argument_file_in . "...\n"); 81 | print("- File size: " . filesize($argument_file_in) . " Bytes.\n"); 82 | print("- Cache size: " . $cache_capacity . " Bytes.\n"); 83 | 84 | $cache = ""; 85 | 86 | while (!feof($file_in)){ 87 | $cache .= fgetc($file_in); 88 | if (strlen($cache) >= $cache_capacity) { 89 | print("- Decrypting cached data...\n"); 90 | fwrite($file_out, xor_string($cache)); 91 | $cache = ""; 92 | } 93 | } 94 | if ($cache !== "") { 95 | print("- Decrypting cached data...\n"); 96 | fwrite($file_out, xor_string($cache)); 97 | } 98 | 99 | fclose($file_in); 100 | fclose($file_out); 101 | 102 | exit("- \033[32mDone!\033[0m Decrypted file is output to " . $argument_file_out . ".\n"); 103 | ?> 104 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | Apache License 2 | Version 2.0, January 2004 3 | http://www.apache.org/licenses/ 4 | 5 | TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 6 | 7 | 1. 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