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encryption util added
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CraZyLegenD committed Apr 2, 2019
1 parent 8d309f8 commit f5659ef
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12 changes: 12 additions & 0 deletions app/src/main/java/com/crazylegend/setofusefulkotlinextensions/MainActivity.kt
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Expand Up @@ -4,8 +4,11 @@ package com.crazylegend.setofusefulkotlinextensions



import android.app.Notification
import android.os.Bundle
import com.crazylegend.kotlinextensions.codestyle.BaseActivity
import com.crazylegend.kotlinextensions.dataStructuresAndAlgorithms.cryptography.EncriptionUtil
import com.crazylegend.kotlinextensions.log.debug


class MainActivity : BaseActivity() {
Expand All @@ -19,9 +22,18 @@ class MainActivity : BaseActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)

EncriptionUtil.generateKey(this)
val textEncrypted = EncriptionUtil.encrypt("asdfasdfasdf")
val textDecrypted = EncriptionUtil.decrypt(textEncrypted)


textEncrypted.debug("Encrypting $textEncrypted")
textDecrypted.debug("Decrypting $textDecrypted")


}




}
227 changes: 227 additions & 0 deletions ...m/crazylegend/kotlinextensions/dataStructuresAndAlgorithms/cryptography/EncriptionUtil.kt
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@@ -0,0 +1,227 @@
package com.crazylegend.kotlinextensions.dataStructuresAndAlgorithms.cryptography

import android.content.Context
import android.os.Build
import android.security.KeyPairGeneratorSpec
import android.security.keystore.KeyProperties
import android.security.keystore.KeyGenParameterSpec
import android.util.Base64
import android.util.Log
import androidx.annotation.RequiresApi
import java.io.ByteArrayInputStream
import java.io.ByteArrayOutputStream
import java.io.IOException
import java.math.BigInteger
import java.security.*
import java.util.*
import javax.crypto.*
import javax.crypto.spec.GCMParameterSpec
import javax.security.auth.x500.X500Principal
import javax.security.cert.CertificateException


/**
* Created by hristijan on 4/2/19 to long live and prosper !
*/

object EncriptionUtil {
private val AndroidKeyStore = "AndroidKeyStore"
private val AES_MODE = "AES/GCM/NoPadding"
private val FIXED_IV = "randomizemsg" // to randomize the encrypted data( give any values to randomize)
private val KEY_ALIAS =
"samplekeyalias" //give any key alias based on your application. It is different from the key alias used to sign the app.
private val RSA_MODE = "RSA/ECB/PKCS1Padding" // RSA algorithm which has to be used for OS version less than M
private var keyStore: KeyStore? = null

fun generateKey(context: Context) {

try {
keyStore = KeyStore.getInstance(AndroidKeyStore)
keyStore!!.load(null)

if (!keyStore!!.containsAlias(KEY_ALIAS)) {

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
val keyGenerator = KeyGenerator.getInstance(KeyProperties.KEY_ALGORITHM_AES, AndroidKeyStore)
keyGenerator.init(
KeyGenParameterSpec.Builder(
KEY_ALIAS,
KeyProperties.PURPOSE_ENCRYPT or KeyProperties.PURPOSE_DECRYPT
)
.setBlockModes(KeyProperties.BLOCK_MODE_GCM).setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_NONE)
.setRandomizedEncryptionRequired(false)
.build()
)
keyGenerator.generateKey()
} else {

// Generate a key pair for encryption
val start = Calendar.getInstance()
val end = Calendar.getInstance()
end.add(Calendar.YEAR, 30)
val spec: KeyPairGeneratorSpec? =
KeyPairGeneratorSpec.Builder(context)
.setAlias(KEY_ALIAS)
.setSubject(X500Principal("CN=$KEY_ALIAS"))
.setSerialNumber(BigInteger.TEN)
.setStartDate(start.time)
.setEndDate(end.time)
.build()
val kpg = KeyPairGenerator.getInstance(KeyProperties.KEY_ALGORITHM_RSA, AndroidKeyStore)
kpg.initialize(spec)
kpg.generateKeyPair()
}
} else {
Log.d("keyStore", "key already available")
}
} catch (e: KeyStoreException) {
e.printStackTrace()
} catch (e: IOException) {
e.printStackTrace()
} catch (e: CertificateException) {
e.printStackTrace()
} catch (e: NoSuchAlgorithmException) {
e.printStackTrace()
} catch (e: InvalidAlgorithmParameterException) {
e.printStackTrace()
} catch (e: NoSuchProviderException) {
e.printStackTrace()
}

}

@Throws(Exception::class)
private fun getSecretKey(): java.security.Key {
return keyStore!!.getKey(KEY_ALIAS, null)
}

@RequiresApi(api = Build.VERSION_CODES.KITKAT)
private fun encryptM(input: String?): String {
val c: Cipher?
try {
c = Cipher.getInstance(AES_MODE)
c!!.init(Cipher.ENCRYPT_MODE, getSecretKey(), GCMParameterSpec(128, FIXED_IV.toByteArray()))
val encodedBytes = c.doFinal(input!!.toByteArray())
return Base64.encodeToString(encodedBytes, Base64.DEFAULT)
} catch (e: NoSuchAlgorithmException) {
e.printStackTrace()
} catch (e: NoSuchPaddingException) {
e.printStackTrace()
} catch (e: InvalidKeyException) {
e.printStackTrace()
} catch (e: InvalidAlgorithmParameterException) {
e.printStackTrace()
} catch (e: IllegalBlockSizeException) {
e.printStackTrace()
} catch (e: BadPaddingException) {
e.printStackTrace()
} catch (e: Exception) {
e.printStackTrace()
}

return ""
}

@RequiresApi(api = Build.VERSION_CODES.KITKAT)
private fun decryptM(encrypted: String): ByteArray? {
val c: Cipher?
try {
c = Cipher.getInstance(AES_MODE)
c!!.init(Cipher.DECRYPT_MODE, getSecretKey(), GCMParameterSpec(128, FIXED_IV.toByteArray()))
val barr = Base64.decode(encrypted, Base64.DEFAULT)
return c.doFinal(barr)
} catch (e: NoSuchAlgorithmException) {
e.printStackTrace()
} catch (e: NoSuchPaddingException) {
e.printStackTrace()
} catch (e: InvalidKeyException) {
e.printStackTrace()
} catch (e: InvalidAlgorithmParameterException) {
e.printStackTrace()
} catch (e: IllegalBlockSizeException) {
e.printStackTrace()
} catch (e: BadPaddingException) {
e.printStackTrace()
} catch (e: Exception) {
e.printStackTrace()
}

return null
}

@Throws(Exception::class)
private fun rsaEncrypt(secret: ByteArray): String {
val privateKeyEntry = keyStore!!.getEntry(KEY_ALIAS, null) as KeyStore.PrivateKeyEntry
// Encrypt the text
val inputCipher = Cipher.getInstance(RSA_MODE, "AndroidOpenSSL")
inputCipher.init(Cipher.ENCRYPT_MODE, privateKeyEntry.certificate.publicKey)

val outputStream = ByteArrayOutputStream()
val cipherOutputStream = CipherOutputStream(outputStream, inputCipher)
cipherOutputStream.write(secret)
cipherOutputStream.close()

val vals = outputStream.toByteArray()
return Base64.encodeToString(vals, Base64.DEFAULT)
}

@Throws(Exception::class)
private fun rsaDecrypt(encrypted: String): ByteArray {
val privateKeyEntry = keyStore!!.getEntry(KEY_ALIAS, null) as KeyStore.PrivateKeyEntry
val output = Cipher.getInstance(RSA_MODE, "AndroidOpenSSL")
output.init(Cipher.DECRYPT_MODE, privateKeyEntry.privateKey)
val barr = Base64.decode(encrypted, Base64.DEFAULT)
val cipherInputStream = CipherInputStream(
ByteArrayInputStream(barr), output
)
val values = ArrayList<Byte>()
cipherInputStream.reader().forEachLine {
values.add(it.toByte())
}

val bytes = ByteArray(values.size)
for (i in bytes.indices) {
bytes[i] = values[i]
}
return bytes
}

fun decrypt(text: String): String {
try {
var d: ByteArray? = ByteArray(0)
if (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
d = EncriptionUtil.decryptM(text)
} else {
try {
d = EncriptionUtil.rsaDecrypt(text)
} catch (e: Exception) {
e.printStackTrace()
}

}
assert(d != null)
return d?.let { String(it, Charsets.UTF_8) }.toString()
} catch (e: Exception) {
e.printStackTrace()
}

return ""
}

fun encrypt(text: String?): String {
var input = text
try {
val d = ByteArray(0)
input = if (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
EncriptionUtil.encryptM(input)
} else {
input?.toByteArray()?.let { EncriptionUtil.rsaEncrypt(it) }
}
return input.toString()
} catch (e: Exception) {
e.printStackTrace()
}

return ""
}
}

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