# 無聲浪
## Original Description> 像密碼 若無線索 只好留下困惑
_IEEE Transactions on Signal Processing, Vol.51, (no.4), pp.1020–33, 2003._
How to:1. Google the description2. Find the GitHub repository written by Microsoft and meet the description3. Download the tool and extract the Hex from audio4.Decode the Hex into ASCII characters5. Profit
## Description (Updated)
> 像密碼 若無線索> 只好留下困惑
_IEEE Transactions on Signal Processing, Vol.51, (no.4), pp.1020–33, 2003._
Walkthrough:
1. Google the description2. Find the [GitHub repository](https://github.com/toots/microsoft-audio-watermarking) written by Microsoft 3. Download the tool (repository) in zip4. Extract the zip, for example, you extract the zip under `D:\Downloads`5. Copy the audio file (`waterwave.wav`) to `D:\Download\microsoft-audio-watermarking-master\build\`6. Open the command prompt and execute the following:```D:\Download\microsoft-audio-watermarking-master\build\detect2003.exe D:\Download\microsoft-audio-watermarking-master\build\watermark.wav```7. Record ass Hex decoded7. Convert all Hex it into ASCII characters, there are many [online tools](https://www.binaryhexconverter.com/hex-to-ascii-text-converter) that can be used8. Profit
有部分參賽者反應 Github 上的工具未能正常執行。請使用命令提示字元(cmd.exe)打開該程式。There is some contester mentioned that the tool on Github cannot be executed normally. Please use command prompt (cmd.exe) to execute the program.
## WriteupWhen we submit the flag, the updated description aren't there yet (yes damn challenge writer aka Byron should update it earlier right...)
We googled the description directly and find the [repository](https://github.com/toots/microsoft-audio-watermarking), downloaded and unzipped the file and when we find there are two exe file for us to use. `watermark2003.exe` is for watermarking the audio file, while `detect2003.exe` is to detect watermarks. Therefore we run the `detect2003.exe` in command promopt (cmd) with the following command:```(Location of file)\microsoft-audio-watermarking-master\build\detect2003.exe (Location of file)\watermark.wav```
It returns the output (only relavent part is listed below, information are neglected) listed in `output.txt` where total of 36 watermarks are detected. Copying the `WM` value of the watermarks, convert them to ASCII by the [ASCII Table](https://www.asciitable.com/) watermark by watermark and log them down in a spreadsheet as listed in `ascii.xlsx`. Finally, it returns us the flag.
## Flag`hkcert21{w0rds_fr0m_3mpt1n3ss}`