With the exponential advancement in networking technologies and multimedia tools, image authentication has become a major challenge. This paper presents a new fragile watermarking method for tampering detection and content recovery. Using 2 x 2 sized image blocks, eight bit watermark is derived by encoding the low frequency component of the discrete cosine transform (DCT) coefficients of the block. The watermark is embedded in the two least significant bit planes of the cover image. A non-linear chaotic sequence based on Arnold cat map is used for block mapping. Experimental results indicate that the proposed algorithm performs better as compared to the existing state of the art methods