Encryption issue in windows phone 8 - c#

I'm designing a Windows Phone 8 app where I need to save certain credentials and message backups as a Parse object. So, while I'm taking data from the user end I want to preserve privacy of the clients. So, why not encrypt it. But then again I need to decrypt it back on client side. Say, there's a message "I'll be late". So, I want it to be encrypted to say "###%&**))^^^__673asdh" and saved in backend which makes absolute no sense to me. Again this encrypted message is read back to the front end client as and when required as the original message that he stored. Please suggest a good library. is AES a good option? Sorry for the question. I'm basically a noob in cryptography! Thanks.

If you are noob in cryptography - do not use encrytion/decryption primitives. Encryption/decryption method is only a part where proper use of the method is very important too. Try to find some crypto library that will do the work for you. At start you can read about Crypto++ library and BounceCastle, inspect the exmaples in this libraries.

Related

Save Key or String securely in app - Xamarin Form

I’ve been following various articles and answers regarding saving
API keys / password / strings still havent gotten specifically that i have been searching.
The idea is to save KEY in a form of string in Xamarin.Form
where the KEY can be accessed while debugging
but should not be exposed if reversed engineered an APK or IPA file.
Stated by one of my colleague ‘Gradle’ used to do similar in android native
yet am unsure on it and where do i get it working in Xamarin.Forms with respect to iOS and Android
Any information related would be much helpful
Your best bet is to make use of SecureStorage this will use the platform specific secure stores to store the data you provide.
As pointed out in comments you should always operate under the assumption that someone will be able to gain access to your code and reverse engineer it. Using the secure stores per platform will require that anyone accessing the device will be able to unlock it via PIN or biometrics, depending on the device.

How can I encrypt files stored in Application.persistentDataPath in Unity?

So I have made a game app using Unity and it stores a lot of information and data in the mobile's data path in this case Android. Now the user can definitely go there and alter the data i.e delete a file and that can lead to my app not working properly. So is there a way to maybe encrypt them so that the user cannot tamper with the data?
Files are of sound, pictures, etc.
You can encrypt files on the disk, but ultimately a player with malicious intentions would be able to slerp the keys used for encryption from the built version of the game. Because of this, I like to call it "Obscufication" rather than "Encryption", but please do try not to store sensitive information in there!
I recommend checking out this StackOverflow answer on how to perform encryption in C#.
If you want more security then you will need a server to store data on. Good luck!

There is a way to make my program send a SMS to a cellphone?

So, I want to implement a function om my C# program, basically what I want to do is find a way to make the program identify the computer which its being accessed so if a not authorize computer try to access it the program will not open.
The way that I want to implement this is at the login screen the person that want to login will need to put their cellphone number and their password but if for some reason a person discover a functionary password and cellphone number and try to access the program with a computer that is not authorized to use the program the program will send a SMS to the functionary cellphone which they put and the person will need to put the aleatory code that will appear in the functionary cellphone, so basically I want to know how and if there is a way to do it, I am a noob with coding,but I appreciate any help.
(sorry for any grammar errors or bad English)
As far as I'm aware, C# does not have a built in way to send SMS. But fear not, there is an online API you can use that is used by a good deal of big businesses. It's called Twilio, and they have a C# library you can access. The only issue that one might have with it is that it does cost money to use their services.
Hope this helps!
Does it need to be an SMS? If not, you can use the Time-Based One-Time Password Algorithm to have one-time codes. There are several .NET libraries available that provide this functionality.
Depending on the cell provider, you can have your c# application send an email to a phone # and the recipient will see that message in their text conversations. I've done this with AT&T sending an email to phonenumber#mms.att.net. Of course you will have to deal with different providers and how/if they accommodate this feature.

is File.Encrypt Method safe? Encrypt File Windows Phone

I have a Windows Phone application which create and has access to personal data in a txt file. I want something like:
The application asks the user to insert his password , and if it is correct , it decrypts runtime the data and makes the data accessible.
What's the right way to encrypt this data?
I search something that is simple to use and is very safe. I've tried to search in the web and i've found this:
http://msdn.microsoft.com/en-us/library/system.io.file.encrypt%28v=vs.110%29.aspx
But is it safe? There's anybody that have used it? How it works?
Sorry for my poor english. Thank you.
There is a whole article about encrypting data on MSDN: http://msdn.microsoft.com/en-us/library/windows/apps/hh487164%28v=vs.105%29.aspx
Just use ProtectedData.Protect and ProtectedData.Unprotect. Both methods take the data and salt as paremeters, so use the user`s password as salt.

Using agsXMPP , can it send images?

I found this lib here
http://www.ag-software.de/agsxmpp-sdk/
hacked on this example here:
http://www.dotnetcurry.com/ShowArticle.aspx?ID=346
It works pretty well actually but I am wondering if one could rig up a message thats an image that would show up in the others (google talk client) or some other client for display? I poked around on the web, couldn't figure out definitively if this is possible...their site says the api supports XML-RPC, could that do it?
Just want to know im not going down a dead end for this functionality...if XMPP jabber even supports it.
This library seems not to support XEP 0231, the specification that "defines an XMPP protocol extension for including or referring to small bits of binary data in an XML stanza."

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