Encrypt/Decrypt a file

cncncn · May 15, 2013

So, there is my problem. I need to encrypt files (pdf, jpg, zip) and to decrypt it in the initial format. I read Encryption and RandomAccessFile library but it seems like it can only be used for data.
Is there a way to convert file to data and vice versa ?
Or is there another library who can do endrypt/decrypt?

I hope I was clear.
Thanks in advance.

Erel · May 15, 2013

You will need to first read the file into a bytes array, encrypt the array and write it back to a file.

Code for reading a file into a bytes array: http://www.b4x.com/forum/basic4andr...ile-dirassets-solution-wanted.html#post154939

cncncn · May 16, 2013

Thank you

but I have another problem when I want to decrypt the byte array, the app crashes and display that. (My initial file sizes around 11 MB)

B4X:

java.lang.OutOfMemoryError
   at java.io.ByteArrayOutputStream.expand(ByteArrayOutputStream.java:91)
   at java.io.ByteArrayOutputStream.write(ByteArrayOutputStream.java:201)
   at java.util.zip.DeflaterOutputStream.finish(DeflaterOutputStream.java:176)
   at java.util.zip.DeflaterOutputStream.close(DeflaterOutputStream.java:156)
   at anywheresoftware.b4a.randomaccessfile.CompressedStreams.CompressBytes(CompressedStreams.java:122)
   at b4a.example.main._button2_click(main.java:401)
   at java.lang.reflect.Method.invokeNative(Native Method)
   at java.lang.reflect.Method.invoke(Method.java:511)
   at anywheresoftware.b4a.BA.raiseEvent2(BA.java:169)
   at anywheresoftware.b4a.BA.raiseEvent2(BA.java:157)
   at anywheresoftware.b4a.BA.raiseEvent(BA.java:153)
   at anywheresoftware.b4a.objects.ViewWrapper$1.onClick(ViewWrapper.java:63)
   at android.view.View.performClick(View.java:4232)
   at android.view.View$PerformClick.run(View.java:17298)
   at android.os.Handler.handleCallback(Handler.java:615)
   at android.os.Handler.dispatchMessage(Handler.java:92)
   at android.os.Looper.loop(Looper.java:137)
   at android.app.ActivityThread.main(ActivityThread.java:4921)
   at java.lang.reflect.Method.invokeNative(Native Method)
   at java.lang.reflect.Method.invoke(Method.java:511)
   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1038)
   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:805)
   at dalvik.system.NativeStart.main(Native Method)

Is it possible to allow more memory for the decryption or something like that ?

agraham · May 16, 2013

No, it seems that your file is too big to read into memory in its entirety. You will have to do it incrementally reading from the encrypted file and writing the decrypted data to another file.

Encrypt/Decrypt a file

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