A Commutative Encryption and Reversible Watermarking for Fingerprint Image

In this work, authors propose a novel scheme with commutative encryption and reversible watermarking for a fingerprint image. Due to commutative property one can embed and extract watermark in either plain or encrypted fingerprint image, irrespective of order in which encryption or watermarking is applied. The encryption and the watermarking keys are shared using secret key sharing mechanism. The biometric database consists of encrypted and watermarked fingerprint images. After successful authentication, watermarking is inverted to get back the plain fingerprint. The proposed scheme protects many of the vulnerable points of a biometric authentication system. Also native biometric authentication accuracy remains unaffected due to reversible watermarking. As per best of our knowledge, this is the first scheme to include homomorphism between encryption and reversible watermarking. Advantages of the proposed method compared to existing techniques are; 1) higher embedding capacity; 2) better peak signal to noise ratio for the decrypted marked image; 3) use of an optimal key length to preserve security while lowering computational cost; 4) simpler cryptographic key management; 5) smaller side information.