The document summarizes a research paper on embedding a secret watermark image into a QR code image using wavelet transform. It discusses converting a binary logo image into a watermark and inserting it into a selected sub-band of the QR code after decomposing the image using two-level two-dimensional wavelet transform. The watermark can then be extracted from the watermarked QR code without needing the original image by using the predicted values and secret key to determine the embedded bit. Previous digital watermarking techniques are also briefly reviewed, including spatial and frequency domain methods.