与其他应用程序android共享加密的图像

Question

I'm developing an application on android platform to encrypt images and i'm using bouncy castle library and I'm doing fine with the encryption part but now when i get the encrypted image I can't send it through other applications like whatsapp and others because the encrypted image file is not recognized as an image file anymore so i cant send it. so can i add anything to the encrypted image so other applications can recognize it as an image and transmitted through it or do somthing else ... thanks

Answer 1

In order to transmit a ciphered message as an image, you need to define a custom protocol to wrap the ciphertext in some image exchange container format, for example PNG.

I wrote a simple program that encrypts an image (the message) and stores the ciphertext along side some meta information in a PNG-encoded container. The sources are on GitHub and the idea is:

1. generate the secret key
2. write headers to file
3. encrypt the message (an image) and write to file