G7KRBChc

1class Encryptor(private val sharedPreferences: SharedPreferences) {
2    private val ANDROID_KEY_STORE = "AndroidKeyStore"
3
4    private var initVector: ByteArray? = null
5    private var encryption: ByteArray? = null
6    private val TRANSFORMATION = "AES/GCM/NoPadding"
7
8    @Throws(Exception::class)
9    fun encryptTextWithAES(alias: String, textToEncrypt: String): ByteArray? {
10        var alias = alias
11
12        alias = alias + "_AES"
13
14        val cipher = Cipher.getInstance(TRANSFORMATION)
15        cipher.init(Cipher.ENCRYPT_MODE, getSecretKey(alias, KeyProperties.KEY_ALGORITHM_AES))
16
17        initVector = cipher.iv
18        encryption = cipher.doFinal(textToEncrypt.toByteArray(StandardCharsets.UTF_8))
19        val base64InitVector = Base64.encodeToString(initVector, Base64.NO_WRAP)
20        val base64Encryption = Base64.encodeToString(encryption, Base64.NO_WRAP)
21        sharedPreferences.edit().putString(alias + "_initVector", base64InitVector).apply()
22        sharedPreferences.edit().putString(alias + "_encryption", base64Encryption).apply()
23
24        Log.d("AndroidKeyStore", "aliases: " + getAllAliasesInTheKeystore())
25        return encryption
26    }
27
28    @Throws(Exception::class)
29    private fun getAllAliasesInTheKeystore(): ArrayList<String> {
30        val keyStore = KeyStore.getInstance("AndroidKeyStore")
31        keyStore.load(null)
32        return Collections.list(keyStore.aliases())
33    }
34
35    @Throws(Exception::class)
36    private fun getSecretKey(alias: String, algorithm: String): SecretKey {
37
38        val keyGenerator: KeyGenerator
39
40        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
41            keyGenerator = KeyGenerator.getInstance(algorithm, ANDROID_KEY_STORE)
42            keyGenerator.init(KeyGenParameterSpec.Builder(alias, KeyProperties.PURPOSE_ENCRYPT or KeyProperties.PURPOSE_DECRYPT)
43                    .setBlockModes(KeyProperties.BLOCK_MODE_GCM)
44                    .setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_NONE)
45                    .build())
46        } else {
47            keyGenerator = KeyGenerator.getInstance(KeyProperties.KEY_ALGORITHM_AES, ANDROID_KEY_STORE)
48            keyGenerator.init(SecureRandom.getInstance(KeyProperties.KEY_ALGORITHM_AES))
49        }
50        return keyGenerator.generateKey()
51    }
52
53    fun encryptTextWithRSA(alias: String, textToEncrypt: String): ByteArray? {
54        var alias = alias
55        alias = alias + "_RSA"
56        var publicKey: Key? = null
57        var privateKey: Key? = null
58        try {
59            getAllAliasesInTheKeystore()
60            val kpg = KeyPairGenerator.getInstance(KeyProperties.KEY_ALGORITHM_RSA, ANDROID_KEY_STORE)
61            kpg.initialize(1024)
62            val kp = kpg.genKeyPair()
63            publicKey = kp.public
64            privateKey = kp.private
65        } catch (e: Exception) {
66            e.printStackTrace()
67        }
68
69        // Encode the original data with RSA private key
70        var encodedBytes: ByteArray? = null
71        try {
72            val c = Cipher.getInstance("RSA")
73            c.init(Cipher.ENCRYPT_MODE, privateKey)
74            encodedBytes = c.doFinal(textToEncrypt.toByteArray())
75            val base64PublicKey = Base64.encodeToString(publicKey!!.encoded, Base64.NO_WRAP)
76            val base64Encrypted = Base64.encodeToString(encodedBytes, Base64.NO_WRAP)
77
78            sharedPreferences.edit().putString(alias + "_publicKey", base64PublicKey).apply()
79            sharedPreferences.edit().putString(alias + "_encryption", base64Encrypted).apply()
80        } catch (e: Exception) {
81            e.printStackTrace()
82        }
83        return encodedBytes
84    }
85}