I am building a Monotouch application which downloads data from the server encrypted using AES. I then need to decrypt this data when the file is accessed.
What is the best way for doing this using MonoTouch? iOS AES decryption is apparently hardware accelerated and so I would ideally like to call into CCCrypt. I am a bit of a n00b to MonoTouch so does anyone know how to do this?
Or alternatively is there a better approach to doing AES decryption in MonoTouch?
MonoTouch provides AES support inside it's class library, e.g. the RijndaelManaged class.
However you need to know a bit more about how it was encrypted (cipher mode, padding mode, key size) to be able to decrypt a file. Also depending on the file size you might want to decrypt it in memory (safer) if it's small or to a temporary file (if large).
Notes:
Rijndael is the original name of the algorithm that got selected to be AES;
AES is a subset of Rijndael (only one block size, 128 bits) so you can do everything AES supports using RijndaelManaged;
At the moment MonoTouch does not use CommonCrypto (it uses the managed implementation from Mono) so you won't get hardware acceleration. This will likely change in future releases (and will be compatible, i.e. simply re-compile, for people who used RijndaelManaged in their applications).
EDIT
MonoTouch 5.3.3 (alpha) now default to use CommonCrypto implementations, including hardware acceleration (when available) for AES and SHA1.
If you are interested in encrypting data at rest (i.e. a database) under MonoTouch SQLCipher might be a good option (http://sqlcipher.net). The MonoTouch provider for SQLCipher provides SQLite full database encryption using AES-256 (http://sqlcipher.net/sqlcipher-for-monotouch). There is also a companion library for Mono on Android, which provides the same API and features for android (http://sqlcipher.net/sqlcipher-on-mono-for-android)
Disclosure: I work for Zetetic, the author of SQLCipher.
Related
I need to implement jcryption in IOS. I have gone through the library it uses Rijndael encryption internally to encrypt the data.
I have tried AES256EncryptWithKey but it is not giving me expected encryption key.
Any help on this would be nice. Thanks
Rijndael with a 128-bit block size is AES. Use Common Crypto on iOS, it uses the hardware encryption engine. There are several ObjC AES answers here on SO, see iOS AES Encryption.
For a detailed answer you will need to provide your usage information on jCryption.
Also notice that jCryption has been discontinued. If you are trying to use jCryption in place of HTTPS the correct solution is to use HTTPS, see jCryption.
I am developing an app that stores PDF files. These files should be stored secure, i. e. encrypted. I also found some libraries that extend NSData with AES en/decryption. But then I read, that iOS supports hardware encryption via AES. Is the NSData library really necessary if they both provide AES256 encryption?
If there are differences, which way is more secure? Also.. how do I activate the hardware encryption? Or is this a global setting that applies to all apps? I guess that the files become decrypted after the device is unlocked? So if someone cracks my phone he has also access to the decrypted files? But if I do the encryption by myself and connect the decryption with a SHA hashed password that is stored in the keychain the files might still be inaccessible?
Edit:
Did I get it all wrong and my library (AQToolkit) is just some kind of API for the built-in hardware encryption and I am basically talking about the same thing?
I heartily recommend RNCryptor, which uses Apple's own Security.framework guaranteeing hardware encryption/decryption if possible. It's incredibly easy to use in the default case (AES-256 with 10k iterations of PBKDF2). It's not an encryption library per se, but rather an Obj-C packaging of the open source Common Crypto C library. Check it out.
I've worked with Java cryptography for many years. Now, we have a requirement to write an iOS application that will send encrypted payloads from the mobile device to a Java service. I've begun working with the iOS crypto support (CommonCrypto, etc.) and have found it a bit more difficult. The JCE has a very clean, concise API, so I've clearly gotten spoiled. In contrast, iOS cryptography is a far more difficult API to work with.
Are there any simplified crypto libraries or wrappers around CommonCrypto that provide a more concise API? In particular, we need:
Key generation (both symmetric and asymmetric)
Encryption/decryption of data
Digital signatures (SHA1withRSA, for example)
Hashing
RSA, 3DES, and AES support
I know I've seen a sample class or two that wraps AES encryption, for example. I'm looking for something a bit richer and more full-featured. Anyone have any suggestions?
You can use openSSL inside your iOS app, for ease of use you can use the SSCrypto library by septicus.
From the septicus site:
SSCrypto.framework provides a simple wrapper around OpenSSL library
functions for encryption, decryption (both symmetric and RSA) and
checksums. It also encodes and decodes base64 data and can generate
both private and public RSA keys. A test tool is included in the
project. Click here to see the main.m file that comes with SSCrypto
for examples of it's use.
A colleague provided me two text files he encrypted using GNUPG, AES128/AES256 with no salt.
Using the following example, https://stackoverflow.com/a/1400596/300972, I tried to decrypt both files in an iOS application, one using the AES256 example, the second by modifying the algo to kCCAlgorithmAES128 and keysize to kCCKeySizeAES128.
Loading the files to an NSData object proved successful; I am able to output the NSData. However, on decrypt they always fail with kCCDecodeError (-4304). I thought it may be the padding, so we tried different variations, the original being kCCOptionPKCS7Padding, still the same error. I tried a padding of 0, which provides a truncated NSData object which I cannot create an NSString from. (UTF8 encoded).
Has anyone been successfully able to decrypt a file encrypted using GNUPG in an iOS environment? Can you provide us with lessons learned?
GnuPG writes in the OpenPGP file format (RFC-4880). This is a fairly complicated format and you would need to parse it before you can even begin to decrypt the data. GnuPG also compresses the data before it encrypts it. And it uses "OpenPGP's variant of Cipher Feedback (CFB) mode." While iOS 5 supports CFB, this isn't quite the same as RFC-4880. For instance, they don't use a normal IV, and they synchronize in a novel way to provide a "quick check" that is incompatible with standard CFB. Then there's their String-to-Key (S2K) algorithms, which are not the same as PBKDF2.
In short, CommonCryptor is the last in a long series of steps of tearing this down to something to hand to AES. You could look at libgcrypt, but its LGPL license is generally incompatible with iOS development. You should probably investigate other OpenPGP implementations. I know there are some in JavaScript (which is crazy, but could still work without creating licensing headaches). Maybe Cryptlib (which has a commercial license).
Personally, I'd go with some other encryptor if you can. OpenSSL, while not particularly secure, is very portable, and as easy to use as a commandline app. RNCryptor can read and write it on iOS.
You can check ObjectivePGP framework.
I am building an application which is talking to my .Net WebService. Application is transmitting some sensitive client information to my WebService which I want to encrypt before I wrap it in the SOAP Envelop. And web service will decrypt it on the other side before using it.
Can someone suggest me how to achieve this. I know .Net has some security which allow you to do some authentication and encryption but I dont want to go to that path at this stage, as I want to make data secure going to and from the iOS device to my webservice.
If any tutorial or example exists please let me know as this is first time I am using encryption decryption.
AES is available on pretty much every platform. What you have to do is to make sure that everything else is the same on both platforms:
1.The same mode; use either CBC or CTR mode.
2.The same IV; set it explicitly, don't use the default because it will often be different on different systems.
3.The same key; obvious, but they need to be the same at the byte level because text can be encoded differently on different systems. Explicitly state the encoding you are using.
4.The same padding; for AES use PKCS7, again don't rely on the default which may be different on different systems.
Whatever you chose do set things explicitly and don't rely on defaults. Defaults can differ between systems and any difference will cause decryption to fail.
Use an HTTPS connection. This will encrypt your entire connection, and it's trivial to use and built in to both the iPhone and .NET.