From 6ac5fd3e048a69fd6af6022a0ef416f8b379c85a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Flesch=20Tam=C3=A1s?= <tamas.flesch@gmail.com>
Date: Thu, 2 May 2024 11:09:06 +0200
Subject: [PATCH] encrypt and decrypt a message with the java cipher class

---
 .../hu/saborsoft/blockchain/TestChipher1.java | 46 +++++++++++++++++++
 1 file changed, 46 insertions(+)
 create mode 100644 src/main/java/hu/saborsoft/blockchain/TestChipher1.java

diff --git a/src/main/java/hu/saborsoft/blockchain/TestChipher1.java b/src/main/java/hu/saborsoft/blockchain/TestChipher1.java
new file mode 100644
index 0000000..8174f1b
--- /dev/null
+++ b/src/main/java/hu/saborsoft/blockchain/TestChipher1.java
@@ -0,0 +1,46 @@
+package hu.saborsoft.blockchain;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.crypto.Cipher;
+import javax.crypto.KeyGenerator;
+import javax.crypto.SecretKey;
+import java.security.SecureRandom;
+
+public class TestChipher1 {
+
+    public static final String MESSAGE = "If you were a drop of tear in my eyes";
+
+    private static final Logger LOG = LoggerFactory.getLogger(TestChipher1.class);
+
+    public static void main(String[] args) throws Exception {
+        LOG.debug("Original message: {}", MESSAGE);
+        SecretKey key = createSecretKey();
+
+        // encrypt the original message
+        Cipher encrypter = initCipher(Cipher.ENCRYPT_MODE, key);
+        byte[] cipherText = encrypter.doFinal(MESSAGE.getBytes());
+        LOG.debug("Encrypted text: {}", new String(cipherText));
+
+        // it is not mandatory, we can modify the type of the first cipher object but in the real world
+        // this would be the case, a new cipher object for decryption
+        Cipher decrypter = initCipher(Cipher.DECRYPT_MODE, key);
+        byte[] decoded = decrypter.doFinal(cipherText);
+        LOG.debug("Decoded string: {}", new String(decoded));
+    }
+
+    private static SecretKey createSecretKey() throws Exception {
+        KeyGenerator keyGenerator = KeyGenerator.getInstance("AES");
+        SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
+        keyGenerator.init(sr);
+        return keyGenerator.generateKey();
+    }
+
+    private static Cipher initCipher(int cipherMode, SecretKey key) throws Exception {
+        Cipher cipher = Cipher.getInstance("AES");
+        cipher.init(cipherMode, key);
+        return cipher;
+    }
+
+}