Hi,
I'm trying to encrypt image files on Android with password based
encryption. To save the encrypted image I just do this:
FileOutputStream fos = new FileOutputStream(thumbnailFile);
CipherOutputStream cos = new CipherOutputStream(fos, encryptCipher);
Bitmap thumbnail = Bitmap.createScaledBitmap(bm2, 140, 140, true);
thumbnail.compress(Bitmap.CompressFormat.JPEG, 80, cos);
and to read it, this:
FileInputStream fis = new FileInputStream(f);
CipherInputStream cis = new CipherInputStream(fis, decryptCipher);
Bitmap b = BitmapFactory.decodeStream(cis);
but the Bitmap ends up as null. The code works when I bypass the
encryption; that is when I use the File(Input|Output)Streams rather
than the Cipher(Input|Output)streams.
My Ciphers are created as follows:
public void initCiphers(char password[]) {
PBEKeySpec pbeKeySpec;
PBEParameterSpec pbeParamSpec;
SecretKeyFactory keyFac;
byte[] salt = {
(byte)0xc7, (byte)0x73, (byte)0x21, (byte)0x8c,
(byte)0x7e, (byte)0xc8, (byte)0xee, (byte)0x99
};
int count = 20;
pbeParamSpec = new PBEParameterSpec(salt, count);
pbeKeySpec = new PBEKeySpec(password);
try {
keyFac = SecretKeyFactory.getInstance("PBEWithMD5AndDES");
SecretKey pbeKey = keyFac.generateSecret(pbeKeySpec);
encryptCipher = Cipher.getInstance("PBEWithMD5AndDES");
decryptCipher = Cipher.getInstance("PBEWithMD5AndDES");
encryptCipher.init(Cipher.ENCRYPT_MODE, pbeKey, pbeParamSpec);
decryptCipher.init(Cipher.DECRYPT_MODE, pbeKey,
pbeParamSpec);
}
catch (Exception e) { Log.v("tag", e.toString()); }
}
I don't get any exceptions.
There is obviously some problem with using Cipher(Output|Input)Streams
with the android functions for encoding and/or decoding images, but
since those functions are opaque and there are no exceptions, its hard
to know what it is. I suspect it has to do with padding or flushing.
Any assistance would be gratefully appreciated.
Matthew Fleming, MD
DermVision, LLC
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