1. 在Android Studio中创建新的C++文件，命名为"Crypto.cpp"。

2. 在"Crypto.cpp"文件中，添加以下代码：

#include 
#include 
#include 
#include 
#include 

#define ALOGE(...) __android_log_print(ANDROID_LOG_ERROR, "Crypto", __VA_ARGS__)

extern "C" {
    JNIEXPORT jstring JNICALL Java_com_example_myapp_MainActivity_getSecretKey(JNIEnv* env, jobject instance);
};

JNIEXPORT jstring JNICALL Java_com_example_myapp_MainActivity_getSecretKey(JNIEnv* env, jobject instance) {
    std::string key = "my_secret_key";
    std::string encryptedKey = "";
    
    // Perform your encryption algorithm here
    
    return env->NewStringUTF(encryptedKey.c_str());
}

3. 在AndroidManifest.xml文件中，在"application"标签内添加以下代码：

4. 在build.gradle文件中，添加以下代码：

android {
    ...
  
    defaultConfig {
        ...
        externalNativeBuild {
            cmake {
                cppFlags "-std=c++11 -O0 -Wall -Werror"
                arguments "-DANDROID_TOOLCHAIN=clang", "-DANDROID_STL=c++_shared"
            }
        }
    }

    externalNativeBuild {
        cmake {
            path "CMakeLists.txt"
        }
    }
}

dependencies {
    ...
    implementation 'com.android.support:support-annotations:28.0.0'
}

5. 在"CMakeLists.txt"文件中，添加以下代码：

# Sets the minimum version of CMake required to build the native library.

cmake_minimum_required(VERSION 3.4.1)

# Creates and names a library, sets it as either STATIC or SHARED,
# and provides the relative paths to its source code.

include_directories(src/main/cpp)

add_library(
    native-lib
    SHARED
    src/main/cpp/Crypto.cpp)

find_library(
    log-lib
    log)

# Links your native library against one or more other native libraries.
target_link_libraries(native