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Reach high security with libsodium on Android

I have no longer supported AES algorithms. Still need it, you can check out tag: v2.2.

• Use CHACHA20 instead of AES. I have to mention that TLS1.3 use CHACHA20 on mobile devices too. It is high-performance for the ARM architecture.

• Hide native function in JniOnload

• Use signature verification to avoid second-packaged. (It prevents hackers call your JNI method directly.)

• key exists in the symbol table, and hides the character table. This approach has been deprecated due to discard reason issues5

• Obtain the key from a complex function, to hide the key, currently, the function is a simple solution. (Complex solution: divide the Key into several pieces, store them in different C files, and finally splice them together. This function should be complicated to write and increase the decompiling difficulty.)

• Use "obfuscator" to confuse C code, how to deobfuscate it?

• Supporting x86 of obfuscation. A link at the bottom is a tutorial for configuring obfuscation.

• Anti-debugging. Currently, I put a simple solution into code, but there are complicated and sophisticated solutions. I recommend determining whether it is traced in every encryption and decryption. You can add other complicated algorithms to your fork.

• Detecting device is an emulator during runtime. This feature comes from my another repo Check_Emulator_In_NDK

• TODO: Prevent SO file injecting from hackers.

build & run it.

click to expand.

1. preparation：

run the shell : ./build_libsodium_for_all_android_abi.sh When you run the shell, some error you may got some error like this: env: python: No such file or directory , `See "config.log" for more details or others.

Please, take time to solve them.

If the shell runs well, many files, such as .a & .so, will be copied into aesjni/src/main/jni/sodium_include/. Also, you would see All of static libs has been moved into ...... at terminal.

1. click run app from ADB to look at logcat， some result of execution will be there

how to integrate it into my project?

click to expand.

a. generating a chacha20 key:

run test_in_exexutaing.sh, and look at logcat. It will generate key and nonce. You can paste it into JNIEntry.c.

b. Set ndk.dir in local.properties. Some NDK versions have not been tested you may encounter build errors from them.

c. As you integrate it into the project, please modify class names and method names, don't expose the name of the encryption algorithm, modify the C function of key storage from my code.

d. Generate and modify signatures.

d.1. Generate Keystore file(You should jump this step in case you already have Keystore.)

# my generate record:
mkdir keystore
cd keystore/
keytool -genkey -alias client1 -keypass 123456 -keyalg RSA -keysize 1024 -validity 365 -storetype PKCS12 -keystore ./androidyuan.keystore

d.2. Modify hash of your keystore and pkg-name in check_signature.h.

As you obtain the hash, you should use this method: getSignature(), to get.

Please copy the keystore hashcode and package name into check_signature.h.

Remind: SO file will become bigger

The size of the confused SO file may be three times the size of the original SO file. If the size bothers you, you can disable obfuscator-lvvm. It is unnecessary.

In addition, what I have to tell you:

Because you need to do signature verification, I can't provide jcenter dependencies, pls forgive me!

Even though this code is very safe, I am still against storing keys in code. The key that shouldn't be constant should be temporary and generated. If you know how SSL works, you may think that asymmetric encryption transferring the key is the safest in the world. If you don’t know how SSL works, I recommend a blog from Cloudflare: what-is-asymmetric-encryption

To confuse native code, you need to modify the externalNativeBuild in the aesjni/build.gradle and configure the Obfuscator-LLVM under the NDK.

This is my NDK configuration obfuscator tutorial: Obfuscator-LLVM-4.0-BUILD-NDK.

In another way, you can build it on docker. Maybe you think configuring Obfuscator-LLVM is really difficult. I recommend using docker : github.com/nickdiego/docker-ollvm.

How do other languages ​​work together with encryption and decryption?

If you got a crash, you can look into FigureOutJNICrash.md to find where this code crashed at.

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Legal

If you live in China, you should take care of checking apk signature. In this code, I use PackageManger which may be misunderstood to collect a list of apps installed. You should look at 工信部整治八项违规.

Contributing

In case you would like to add information to this repository or suggest some ideas, please use one of the following options:

• Create an Issue.
• Send me Pull Requests

Contributor

https://github.com/larry19840909

https://github.com/zxp0505

https://github.com/baoyongzhang

Thanks

Libsodium Algorithm from: https://github.com/jedisct1/libsodium

Native code obfuscator: obfuscation-o-llvm-ndk