Text Watermarking using Sinusoidal Greyscale Variations of Font based on Alphabet Count

In this paper, an imperceptible, fragile text watermarking algorithm has been proposed. The font color of each alphabet in the text document is varied in the greyscale in accordance with a sine function. The amplitude for the same is generated using a hash function. The authenticity of the received document can be verified by comparing the actual color values of the letters in the document with the expected values generated by the sine function. This scheme is highly sensitive to various malicious text related tampering attacks hence preserving the integrity of the document. Unlike earlier methods, the proposed algorithm provides tamper detection while maintaining watermark invisibility. The attack analysis illustrates that the scheme is efficient and secure.