AndroidX의 Android Security를 활용한 SharedPreferences 암호화

build.gradle(app)에 아래와 같은 dependency 추가

dependencies {
	...
	implementation 'androidx.security:security-crypto:1.1.0-alpha01'
	...
}

 

import android.content.Context
import android.content.SharedPreferences
import android.security.keystore.KeyGenParameterSpec
import android.security.keystore.KeyProperties
import android.util.Log
import androidx.security.crypto.EncryptedSharedPreferences
import androidx.security.crypto.MasterKey

class SharedUtil(private val context: Context) {
    companion object{
        private const val TAG = "SharedUtil"
        private const val MASTER_KEY_ALIAS = "_androidx_security_master_key_"
        private const val KEY_SIZE = 256
        private const val PREFERENCE_FILE_KEY = "_preferences"
    }

    private val sharedPreferences: SharedPreferences by lazy {
        val spec = KeyGenParameterSpec
            .Builder(MASTER_KEY_ALIAS, KeyProperties.PURPOSE_ENCRYPT or KeyProperties.PURPOSE_DECRYPT)
            .setBlockModes(KeyProperties.BLOCK_MODE_GCM)
            .setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_NONE)
            .setKeySize(KEY_SIZE)
            .build()

        val masterKey = MasterKey
            .Builder(context)
            .setKeyGenParameterSpec(spec)
            .build()

        EncryptedSharedPreferences.create(
            context,
            context.packageName + PREFERENCE_FILE_KEY,
            masterKey,
            EncryptedSharedPreferences.PrefKeyEncryptionScheme.AES256_SIV,
            EncryptedSharedPreferences.PrefValueEncryptionScheme.AES256_GCM
        )
    }

    fun putAny(key: String, value: Any){
        val editor = sharedPreferences.edit()

        with(editor) {
            when (value) {
                is Int -> {
                    Log.d(TAG, "Input Key is $key, Int Value is $value ")
                    putInt(key, value)
                }
                is String -> {
                    Log.d(TAG, "Input Key is $key, String Value is $value ")
                    putString(key, value)
                }
                is Boolean -> {
                    Log.d(TAG, "Input Key is $key, Boolean Value is $value ")
                    putBoolean(key, value)
                }
                else -> throw IllegalArgumentException("잘못된 인자입니다.")
            }
            apply()
        }
    }

    fun getString(key: String) = sharedPreferences.getString(key, "")

    fun getNumber(key: String) = sharedPreferences.getInt(key, 0)

    fun getBoolean(key: String) = sharedPreferences.getBoolean(key, false)
}

 

암호화된 SharedPreferences의 파일 내용을 보고싶다면

View > Tool Windows > Device File Explorer 창을 열고

data > data > 패키지 네임 > 위에서 지정한 이름의 파일을 열면

아래와 같이 암호화가 되어있는 걸 확인할 수 있다.