SharedPreferences / EncryptedSharedPreferences

SharedPreferences / EncryptedSharedPreferences 의 사용법입니다.

 

 

 

1. SharedPreferences

 

간단하게 아래와 같이 구현해줄 수 있습니다.

 

class MainActivity : AppCompatActivity() {


    override fun onCreate(savedInstanceState: Bundle?) {

        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val sharedPref = this.getPreferences(Context.MODE_PRIVATE) ?: return
        with (sharedPref.edit()) {
            putString("myString", "keyValue")
            apply()
        }


        val highScore = sharedPref.getString("myString", "defaultValue")

        Log.e("a", highScore.toString())

    }


}

 

이 친구를 찾아보면 아래와 같이 평문으로 저장된 것을 볼 수 있습니다.

 

 

 

 

이 친구를 암호화 해보겠습니다.

 

 

2. EncryptedSharedPreferences

 

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {

        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val masterKeyAlias = MasterKeys.getOrCreate(MasterKeys.AES256_GCM_SPEC)

        val sharedPreferences = EncryptedSharedPreferences.create(
            "this_is_file_name",
            masterKeyAlias,
            applicationContext,
            EncryptedSharedPreferences.PrefKeyEncryptionScheme.AES256_SIV,
            EncryptedSharedPreferences.PrefValueEncryptionScheme.AES256_GCM
        )

        val editor = sharedPreferences.edit()

        editor.putString("key", "value")
        editor.apply()

    }

}

 

 

3. EncryptedFile

 

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {

        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        // read 파일 쓰기


//        val keyGenParameterSpec = MasterKeys.AES256_GCM_SPEC
//        val mainKeyAlias = MasterKeys.getOrCreate(keyGenParameterSpec)
//
//        val fileToRead = "my_sensitive_data.txt"
//        val encryptedFile = EncryptedFile.Builder(
//            File(applicationContext.filesDir, fileToRead),
//            applicationContext,
//            mainKeyAlias,
//            EncryptedFile.FileEncryptionScheme.AES256_GCM_HKDF_4KB
//        ).build()
//
//        val inputStream = encryptedFile.openFileInput()
//        val byteArrayOutputStream = ByteArrayOutputStream()
//        var nextByte: Int = inputStream.read()
//        while (nextByte != -1) {
//            byteArrayOutputStream.write(nextByte)
//            nextByte = inputStream.read()
//        }
//
//        val plaintext: ByteArray = byteArrayOutputStream.toByteArray()
//


        // Although you can define your own key generation parameter specification, it's
        // recommended that you use the value specified here.
        val keyGenParameterSpec = MasterKeys.AES256_GCM_SPEC
        val mainKeyAlias = MasterKeys.getOrCreate(keyGenParameterSpec)

// Create a file with this name, or replace an entire existing file
// that has the same name. Note that you cannot append to an existing file,
// and the file name cannot contain path separators.
        val fileToWrite = "my_sensitive_data.txt"
        val encryptedFile = EncryptedFile.Builder(
            File(applicationContext.filesDir, fileToWrite),
            applicationContext,
            mainKeyAlias,
            EncryptedFile.FileEncryptionScheme.AES256_GCM_HKDF_4KB
        ).build()

        val fileContent = "MY SUPER-SECRET INFORMATION".toByteArray(StandardCharsets.UTF_8)

        encryptedFile.openFileOutput().apply {
            write(fileContent)
            flush()
            close()
        }

    }

}

 

 

 

 

- 참조

 

https://developer.android.com/training/data-storage/shared-preferences?hl=ko 

키-값 데이터 저장  |  Android 개발자  |  Android Developers

 

https://developer.android.com/topic/security/data?hl=ko 

Android 개발자  |  Android Developers

 

https://www.youtube.com/watch?v=2uResVLUCNI 

 

https://thdev.tech/android/2019/12/21/Android-Security-Library/

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