creazione classe per gestione qr code

src/puntocassa/utils/QrCryptoService.java

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+/*
+ * Click nbfs://nbhost/SystemFileSystem/Templates/Licenses/license-default.txt to change this license
+ * Click nbfs://nbhost/SystemFileSystem/Templates/Classes/Class.java to edit this template
+ */
+package puntocassa.utils;
+
+/**
+ *
+ * @author assis
+ */
+import javax.crypto.Cipher;
+import javax.crypto.spec.GCMParameterSpec;
+import javax.crypto.spec.SecretKeySpec;
+import java.nio.charset.StandardCharsets;
+import java.security.SecureRandom;
+import java.time.OffsetDateTime;
+import java.util.Base64;
+import org.json.JSONObject;
+
+public class QrCryptoService {
+
+    // Chiave AES 256-bit (32 byte) - hardcoded per test
+    private static final byte[] AES_KEY = "0123456789ABCDEF0123456789ABCDEF".getBytes(StandardCharsets.UTF_8);
+
+    // Crea il JSON cifrato da inserire nel QR
+    public static String createEncryptedQr(String uid, OffsetDateTime issuedAt, OffsetDateTime expiresAt) throws Exception {
+        // Crea il payload JSON con i dati utente
+        String payloadJson = new JSONObject()
+                .put("uid", uid)
+                .put("issued_at", issuedAt.toString())
+                .put("expires_at", expiresAt.toString())
+                .toString();
+
+        // Genera un Initialization Vector (IV) da 96 bit
+        byte[] iv = new byte[12];
+        new SecureRandom().nextBytes(iv);
+
+        // Cifra il payload con AES-GCM
+        Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");
+        SecretKeySpec keySpec = new SecretKeySpec(AES_KEY, "AES");
+        GCMParameterSpec gcmSpec = new GCMParameterSpec(128, iv);
+        cipher.init(Cipher.ENCRYPT_MODE, keySpec, gcmSpec);
+        byte[] encrypted = cipher.doFinal(payloadJson.getBytes(StandardCharsets.UTF_8));
+
+        // Codifica IV e dati cifrati in Base64
+        String ivBase64 = Base64.getEncoder().encodeToString(iv);
+        String encryptedBase64 = Base64.getEncoder().encodeToString(encrypted);
+
+        // Costruisce il JSON finale con iv e data
+        JSONObject qrJson = new JSONObject()
+                .put("iv", ivBase64)
+                .put("data", encryptedBase64);
+
+        return qrJson.toString(2); // con indentazione
+    }
+
+    // Decifra il JSON e verifica se è ancora valido
+    public static String decryptAndValidate(String qrJson) throws Exception {
+        JSONObject obj = new JSONObject(qrJson);
+        byte[] iv = Base64.getDecoder().decode(obj.getString("iv"));
+        byte[] encryptedData = Base64.getDecoder().decode(obj.getString("data"));
+
+        // Decrittazione con AES-GCM
+        Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");
+        SecretKeySpec keySpec = new SecretKeySpec(AES_KEY, "AES");
+        GCMParameterSpec gcmSpec = new GCMParameterSpec(128, iv);
+        cipher.init(Cipher.DECRYPT_MODE, keySpec, gcmSpec);
+        byte[] decryptedBytes = cipher.doFinal(encryptedData);
+
+        // Parsing del payload decifrato
+        JSONObject payload = new JSONObject(new String(decryptedBytes, StandardCharsets.UTF_8));
+        String uid = payload.getString("uid");
+        OffsetDateTime issuedAt = OffsetDateTime.parse(payload.getString("issued_at"));
+        OffsetDateTime expiresAt = OffsetDateTime.parse(payload.getString("expires_at"));
+        boolean isExpired = OffsetDateTime.now(expiresAt.getOffset()).isAfter(expiresAt);
+
+        return String.format(
+                "Dati decifrati:\n" +
+                "- UID: %s\n" +
+                "- Emesso: %s\n" +
+                "- Scadenza: %s\n" +
+                "- Stato: %s\n",
+                uid,
+                issuedAt,
+                expiresAt,
+                isExpired ? "SCADUTO" : "VALIDO"
+        );
+    }
+
+    // Test completo della generazione e verifica
+    public static void main(String[] args) throws Exception {
+        //data valida
+        OffsetDateTime issuedAt = OffsetDateTime.now().withNano(0);
+        //data scaduta
+        //OffsetDateTime issuedAt = OffsetDateTime.now().minusMinutes(5).withNano(0);
+        OffsetDateTime expiresAt = issuedAt.plusSeconds(60);
+        String qrJson = createEncryptedQr("TSTTST91A48A271O", issuedAt, expiresAt);
+
+        System.out.println("QR JSON simulato:");
+        System.out.println(qrJson);
+
+        System.out.println("\nVerifica decifratura:");
+        System.out.println(decryptAndValidate(qrJson));
+    }
+}