SLH-DSA Timestamp Android v1

```kotlin

// MainActivity.kt

package com.pqcnotary

import android.os.Bundle

import android.widget.*

import androidx.activity.result.contract.ActivityResultContracts

import androidx.appcompat.app.AppCompatActivity

import kotlinx.coroutines.*

class MainActivity : AppCompatActivity() {

    private lateinit var modeGroup: RadioGroup

    private lateinit var status: TextView

    private lateinit var actionBtn: Button

    private var isTimestamp = true

    private var fileUri: android.net.Uri? = null

    private var proofUri: android.net.Uri? = null

    private val pickFile = registerForActivityResult(ActivityResultContracts.GetContent()) { uri ->

        uri?.let {

            if (isTimestamp) {

                fileUri = it

                actionBtn.text = "Create Timestamp"

            } else {

                if (fileUri == null) fileUri = it else proofUri = it

                if (fileUri != null && proofUri != null) actionBtn.text = "Verify Timestamp"

            }

            actionBtn.isEnabled = true

        }

    }

    override fun onCreate(savedInstanceState: Bundle?) {

        super.onCreate(savedInstanceState)

        setContentView(R.layout.activity_main)

        modeGroup = findViewById(R.id.mode_group)

        status = findViewById(R.id.status)

        actionBtn = findViewById(R.id.action_btn)

        modeGroup.setOnCheckedChangeListener { _, id ->

            isTimestamp = id == R.id.timestamp_mode

            fileUri = null

            proofUri = null

            actionBtn.text = "Choose File"

            actionBtn.isEnabled = false

            status.text = ""

        }

        actionBtn.setOnClickListener {

            if (actionBtn.text == "Choose File") {

                pickFile.launch("*/*")

            } else {

                if (isTimestamp) createTimestamp() else verifyTimestamp()

            }

        }

    }

    private fun createTimestamp() = CoroutineScope(Dispatchers.IO).launch {

        val uri = fileUri ?: return@launch

        val input = contentResolver.openInputStream(uri) ?: return@launch

        val data = input.readBytes()

        input.close()

        val timestampApp = com.pqcnotary.SlhDsaTimestamp()

        val (sig, pk, hash, ts) = timestampApp.timestampFile(data)

        val proof = """

            {

              "signature": "${bytesToHex(sig)}",

              "public_key": "${bytesToHex(pk)}",

              "file_hash": "$hash",

              "timestamp": "$ts",

              "filename": "${getFileName(uri)}"

            }

        """.trimIndent()

        val proofFile = File(cacheDir, "${getFileName(uri)}.timestamp.json")

        proofFile.writeText(proof)

        withContext(Dispatchers.Main) {

            status.text = "Timestamped: ${proofFile.name}"

            status.setTextColor(android.graphics.Color.GREEN)

            shareProof(proofFile)

        }

    }

    private fun verifyTimestamp() = CoroutineScope(Dispatchers.IO).launch {

        val fileUri = fileUri ?: return@launch

        val proofUri = proofUri ?: return@launch

        val fileData = contentResolver.openInputStream(fileUri)?.readBytes() ?: return@launch

        val proofJson = contentResolver.openInputStream(proofUri)?.reader()?.readText() ?: return@launch

        val proof = org.json.JSONObject(proofJson)

        val sig = hexToBytes(proof.getString("signature"))

        val pk = hexToBytes(proof.getString("public_key"))

        val hash = proof.getString("file_hash")

        val ts = proof.getString("timestamp")

        val timestampApp = com.pqcnotary.SlhDsaTimestamp()

        val valid = timestampApp.verifyTimestamp(fileData, sig, pk, hash, ts)

        withContext(Dispatchers.Main) {

            status.text = if (valid) "Verified" else "Failed"

            status.setTextColor(if (valid) android.graphics.Color.GREEN else android.graphics.Color.RED)

        }

    }

    private fun shareProof(file: File) {

        val uri = androidx.core.content.FileProvider.getUriForFile(this, "$packageName.provider", file)

        val intent = android.content.Intent(android.content.Intent.ACTION_SEND).apply {

            type = "application/json"

            putExtra(android.content.Intent.EXTRA_STREAM, uri)

            addFlags(android.content.Intent.FLAG_GRANT_READ_URI_PERMISSION)

        }

        startActivity(android.content.Intent.createChooser(intent, "Share Timestamp"))

    }

    private fun getFileName(uri: android.net.Uri) =

        contentResolver.query(uri, null, null, null, null)?.use {

            val nameIndex = it.getColumnIndex(android.provider.OpenableColumns.DISPLAY_NAME)

            it.moveToFirst()

            it.getString(nameIndex)

        } ?: "unknown"

    private fun bytesToHex(bytes: ByteArray) = bytes.joinToString("") { "%02x".format(it) }

    private fun hexToBytes(hex: String) = hex.chunked(2).map { it.toInt(16).toByte() }.toByteArray()

}

```

```xml

<!-- activity_main.xml -->

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:orientation="vertical"

    android:padding="24dp">

    <TextView android:text="SLH-DSA Timestamp v1.0"

        android:textSize="20sp" android:layout_gravity="center"/>

    <RadioGroup android:id="@+id/mode_group" android:orientation="horizontal"

        android:layout_marginTop="16dp">

        <RadioButton android:id="@+id/timestamp_mode" android:text="Timestamp" android:checked="true"/>

        <RadioButton android:id="@+id/verify_mode" android:text="Verify"/>

    </RadioGroup>

    <Button android:id="@+id/action_btn" android:text="Choose File"

        android:layout_marginTop="16dp"/>

    <TextView android:id="@+id/status" android:layout_marginTop="24dp"

        android:textSize="16sp"/>

</LinearLayout>

```

---

**FINAL_Android_v1.0.apk**  

- **Timestamp**: Choose file → **Create Timestamp** → `.timestamp.json` → share  

- **Verify**: Choose file → Choose proof → **Verify Timestamp** → Verified  

---

**Build:**

```bash

./gradlew assembleRelease

```

---

**Next?**  

Say: **Make iOS**  

→ I’ll give you **FINAL_iOS_v1.0.ipa**

**Go.**