To enhance security of the bitplane decomposition based image encryption methods, this paper introduces a novel image encryption algorithm using a bitplane of a source image as the security key bitplane to encrypt images. Users have the flexibility to choose (1) any existing or newly generated image as the source image; (2) any decomposition method for generating the bitplane; (3) any decomposed bitplane as the security key bitplane; (4) any scrambling method for the bit-level permutation. As an example, this paper also proposes a bit-level scrambling algorithm to change bit positions. Simulations and security analysis are provided to demonstrate an excellent encryption performance of the proposed algorithm. © 2014 Elsevier B.V. All rights reserved.