Add end-to-end encryption

app/build.gradle

@@ -35,6 +35,7 @@ dependencies {
     implementation 'com.android.support:support-v4:28.0.0'
     implementation 'com.google.android.gms:play-services-vision:17.0.2'
     implementation 'com.android.support:support-vector-drawable:28.0.0'
+    implementation 'com.github.joshjdevl.libsodiumjni:libsodium-jni-aar:2.0.1'
     testImplementation 'junit:junit:4.12'
     androidTestImplementation 'com.android.support.test:runner:1.0.2'
     androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'

app/src/main/AndroidManifest.xml

@@ -1,11 +1,12 @@
 <?xml version="1.0" encoding="utf-8"?>
-<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+<manifest xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools"
           package="com.adityapk.zcash.zqwandroid">
 
     <uses-permission android:name="android.permission.CAMERA"/>
     <uses-permission android:name="android.permission.INTERNET"/>
 
     <application
+            tools:replace="android:allowBackup"
             android:allowBackup="true"
             android:icon="@mipmap/ic_launcher"
             android:label="@string/app_name"

app/src/main/java/com/adityapk/zcash/zqwandroid/DataModel.kt

@@ -7,6 +7,9 @@ import com.beust.klaxon.Klaxon
 import com.beust.klaxon.Parser
 import com.beust.klaxon.json
 import okhttp3.WebSocket
+import org.libsodium.jni.NaCl
+import org.libsodium.jni.Sodium
+import java.math.BigInteger
 
 
 object DataModel {
@@ -24,6 +27,43 @@ object DataModel {
         transactions = null
     }
 
+    var secret : ByteArray? = null
+    var nonce  : ByteArray? = null
+
+    fun ByteArray.toHexString() = joinToString("") { String.format("%02x", it) }
+
+    fun init() {
+        val sodium = NaCl.sodium()
+
+        secret = ByteArray(Sodium.crypto_hash_sha256_bytes())
+        Sodium.crypto_hash_sha256(secret, "secret".toByteArray(), "secret".toByteArray().size)
+
+        nonce = ByteArray(Sodium.crypto_box_noncebytes())
+        Sodium.randombytes_buf(nonce, Sodium.crypto_box_noncebytes())
+
+        val message = "test".toByteArray()
+        val noncelen = Sodium.crypto_secretbox_noncebytes().toLong()
+        val nonce = ByteArray(noncelen.toInt())
+        val ciphertextlen = Sodium.crypto_secretbox_macbytes() + message.size
+        val ciphertext = ByteArray(ciphertextlen)
+        val secret = ByteArray(Sodium.crypto_secretbox_keybytes())
+
+        Sodium.randombytes_buf(nonce, noncelen.toInt())
+        Sodium.randombytes(secret, Sodium.crypto_secretbox_keybytes())
+
+        println("Noncelen = $noncelen" )
+        println(BigInteger(nonce.toHexString(), 16))
+
+        var ret = Sodium.crypto_secretbox_easy(ciphertext, message, message.size, nonce, secret)
+        Log.i(TAG, ret.toString())
+
+        val decrypted = ByteArray(ciphertext.size - Sodium.crypto_secretbox_macbytes())
+        ret = Sodium.crypto_secretbox_open_easy(decrypted, ciphertext, ciphertextlen, nonce, secret)
+
+        Log.i(TAG, ret.toString())
+        println("Recovered message=" + String(decrypted))
+    }
+
     fun parseResponse(response: String) : Boolean {
         val json = Parser.default().parse(StringBuilder(response)) as JsonObject
 
@@ -73,7 +113,7 @@ object DataModel {
     }
 
     fun makeAPICalls() {
-        ws?.send(json { obj("command" to "getInfo") }.toJsonString())
+        ws?.send(encrypt(json { obj("command" to "getInfo") }.toJsonString()))
         ws?.send(json { obj("command" to "getTransactions")}.toJsonString())
     }
 
@@ -85,6 +125,29 @@ object DataModel {
 
     }
 
+    fun encrypt(s : String) : String {
+        // Take the string, encrypt it and send it as the payload with the nonce in a Json string
+        val msg = s.toByteArray()
+
+        check(secret != null)
+        check(nonce != null)
+
+        val encrypted = ByteArray(msg.size + Sodium.crypto_secretbox_macbytes())
+
+        // Increment nonce
+        Sodium.sodium_increment(nonce, nonce?.size ?: 0)
+
+        val ret = Sodium.crypto_secretbox_easy(encrypted, msg, msg.size, nonce, secret)
+        if (ret != 0) {
+            println("Encryption failed")
+        }
+
+        val j = json { obj("nonce" to nonce?.toHexString(),
+                          ("payload" to encrypted.toHexString()))}
+
+        return j.toJsonString()
+    }
+
     private val TAG = "DataModel"
 
 }

app/src/main/java/com/adityapk/zcash/zqwandroid/MainActivity.kt

@@ -38,6 +38,8 @@ class MainActivity : AppCompatActivity(), TransactionItemFragment.OnFragmentInte
         // When creating, clear all the data first
         setMainStatus("")
 
+        DataModel.init()
+
         btnConnect.setOnClickListener {
             val intent = Intent(this, QrReaderActivity::class.java)
             intent.putExtra("REQUEST_CODE", QrReaderActivity.REQUEST_CONNDATA)