Abstract
This paper proposes to cryptanalyze a partial image encryption scheme. Security weaknesses were found in the cryptosystem consisting in the generation of the keystream. We then propose a modified version of the partial encryption scheme to enhance its security together with keeping the benefit of encrypting a reduced amount of data. Our contributions can be resumed in two points : we will first show the insecurity of the cryptosystem under study then we will propose a remedy to resist the described attacks.