I understand that the cache is data that is temporarily stored from a specific app. Opening /data/data/com.blah.blah/cache/ using a root file explorer reveals these cache files to me. I am able to open and view those that are an image, but when opening a non-image cache file - usually with a text editor - I get a bunch of Chinese looking characters... I know that basically the apps cache is only viewable by said app, but is there any way to convert file to a human readable text file?
but is there any way to convert file to a human readable text file?
Contact the developers of the app and ask them.
There are a dizzying roster of possible file formats, even among "standard" types. Any given computer program might use one of those file formats, or invent their own, or use one of those formats but encrypt the file, etc. There is no requirement that all computer files contain human-readable material. For all we know, the developers of this app are storing random numbers in these files, specifically to confuse people who try to reverse-engineer their stored data.
Related
I am writing a small medical app as means of trying out my newly learned Android skills. I want to be able to read a text file from a specific folder on the device (not the SD card) where the user can put some medical information (when the app starts upp) without having the user need to pick the file destination, but I am not sure how to implement it. I may also want to write to the file.
The file may change frequently. The truth is, I need to read from a directory with a variable number of subdirectories, each with 4 files in them. It is those files I need to read and then display, but for the sake of simplicity I limited the question to just reading the file. It seems like this would be a file which would be in "Internal Storage/Android/data/com.me.myapp/medical_information", but I am not sure how convenient that would be for the user to constantly have to find the app among all of the app folders, and then navigate to the folder. Where would be the best place to put this folder/file, and how would go about writing/reading from it?
It is preferrable that answers be written in Kotlin, but not essential.
I have an application that I want to develop. The android application is more or less like a book that will allow the users to select a chapter and it will display the whole text in that chapter and a media file for the chapter. Where do you think I can store the text and the media. Should I use json format or sqlite database or I should store both text and media in a folder and access it there. Am really confused because I still want to be able to perform some query on the text search for the text in my application.
You can use binary files, where you load the data sequencial.
Or you use zip-files, in which format many programs store data. Eg .svgz is a zipped version of .svg used by Inkscape, .odf is an open source format used by eg. OpenOffice or LibreOffice (the specification says it could be either a XML- or ZIP-structure.) You can store the text in a file, where in the text it references to other files like images in the zip, like a html-file references to other files on the server in the directory. This can be a json-file or an xml-document or a binary-serialization of an object-structure. There are many zip-libraries out there,. It is a big security risk, if you do not check in the file for references to other files outside the zip, like '../../Documents/myPasswords.txt' (when you are on Windows for example and you use the %temp% directory, this may reference to 'C:/Users/BOB/Documents/myPasswords.txt' when the directory where you unpack to is '%temp%/randomName/'), when unpacking the data to a temporary directory and load a file (however different operating systems treat this differently, Android is more secure than Windows, but the app can crash if you do not check...).
But if you do not care about filesize and if you store the data directly within the app (and not download them from the internet), you just include it in your data-folders.
I am writing an app for my final year project, so it's more so for proof of concept so it doesn't have to be the best app in the world.
It is like a file locker app that you can add and remove files from the app and when they are stored they will be encrypted. There will be a login of some sort for the user to enter and be verified on a DB.
I am still a novice in android so I still have a way to go, but I am getting there!
I was thinking when the file (which could be a doc, pdf, jpg, video file etc) is added to the app it would be stored in the internal storage (from what I have read it seems to be the best place to store app related content) and a record of the name and file type would be added to the DB and also the encrypted file name. So when the user looks at the app they will see a thumbnail of the pic and the file name, kinda like the My Files app shows up files within a folder.
My question is it best not to store the file directly into the DB but just use the DB as a reference with the file details, if so how could this be done?
Also I was thinking that an AES 128bit encryption method would be best suited for this. I have tried a couple of encryption examples but have only been able to do this with a txt file, when i tried it with a jpg the app just sat there and did nothing. It showed the encrypted and decrypted jpg but this was not viewable.
Would anyone be able to suggest a good way of encrypting any file type that would suit for my app?
Any help would be greatly appreciated!
Cheers,
Owen
If you want to do this properly, here are a few tips:
Don't store files in the database, unless you know in advance that they're going to be really titchy. Store them somewhere else, with a reference to them in the database.
The best place for them if they're smallish is internal storage in the app's private file space. But if you want to be able to store encrypted arbitrary data then you'll need to hit external storage.
Don't store the decryption key!
Ideally, you should find a way not to write the file anywhere when you decrypt it. That might not be possible, though, if you need to open it in another application afterwards. If you write the encrypted files to external storage, you should at the very least write the decrypted version to internal storage where there's some operating system protection against other apps reading it. If you write the decrypted file to external storage, anything will be able to get at it.
AES with a 128-bit key will do you fine.
I'm developing an ebook reader app for Android. The special books for this app are zipped files of some html/css/js/image/... files which are in a server and will be downloaded by the app. Each zipped file may have 1-5 MB and if extracted, a lot more than that.
I was wondering, regarding to android guidelines, where is suitable to
Put the zipped book files?
Put the extracted files when they are being used?
Well, if you actually need to save that data when app finishes, you should use sd-card, since it has more space, but if you only download image one time, just to show it on screen than use internal storage. Also consider your lowest API since that will be phone with least storage, and your app needs to work there as well as on new devices. Either way if you have to make several files while extracting data, use internal storage because it will be faster, and move it later to sd card if you actually need to save it.
I'm making an Android app that generates an Excel file using JExcelApi. The content of the fiel is also available as plain text but it's not stored anywhere (I'm using it for displaying it on a TextView; the content isn't too complex).
To simplify things I store the Excel file on the SD card root directory. I know it's not good practice, but this app is not meant for wide distribution and it's only used for internal purposes in my company, so I'm not too worried about it. When the app generates the file, you can either press a "send XLS" button on the main view which will create a SEND_ACTION intent so you can send the file through email, Dropbox or whatever, or you can just simply plug the phone to a computer, mount it as USB storage and get the file.
However, soon we're going to need to send the app to some of our clients and some changes need to be done. We don't want our clients to access the XLS file, so I need to protect it somehow. Unfortunately, JExcelApi does not support password protected files, so I need to find an alternative way to protect it.
Regarding the "send" button: I was thinking about adding a simple password dialog, so that the user needs to type in a hard-coded password first before the intent is sent. I still haven't taken a look at this, though.
What worries me the most is the XLS file. Ideally, it should still be available on the SD card's root folder, but I realize that this may make things much harder than necessary. Using the app's private storage would be option because the file would be "invisible", but this can be easily beaten by using a rooted phone. I've taken a look around the Cipher class but I'm not sure how I could apply it to my case: the JExcelApi manages the opening and saving of files by itself and I can't use CipherOutputStream to save the file; I also need to be able to decrypt the file on a PC.
What should I do? Is there any way to encrypt the file in Android in a way that would make it possible to decrypt it on a PC? Should I find some other Excel APIs that support password protection (are there even any)?
About the security requirements: the content of the report is not critical and it wouldn't be a big deal if our clients got access to it (I mean, the content itself is displayed on screen!), but I'd like to make it annoying enough that our clients would cease to insist accessing the XLS file, if they ever tried to.
TL;DR: how do I encrypt any kind of file in Android?
I'm not very familiar with encryption on Android, but there's the Bouncycastle library that can be used for encrytion on Android. There might be some pitfalls, but apparently you can also use Android's own Cipher class for en-/decrypting using different algorithms.
If you want to share the encrypted data you'll have to have a shared key in order to let the recipient decrypt it.