BAEL-1371 - Guide to Cipher class (#3150)

* Bean Injection Types

* Bean Injection Types

* Bean Injection Types

* Bean Injection Types -  Added / Fixed tests

* BAEL-1371 Encryptor class

* BAEL-1371 Modified Encryptor class, added encryptor test

* BAEL-1371 Modified Encryptor class, added encryptor test

* BAEL-1371 removed spring core files

* BAEL-1371 Update test, new line for "when" and "then" logic

* BAEL-1371 Fixed tests

* BAEL-1371 cleanup and assertj assertions

core-java/src/main/java/com/baeldung/cipher/Encryptor.java

@@ -0,0 +1,35 @@
+package com.baeldung.cipher;
+
+import javax.crypto.*;
+import javax.crypto.spec.SecretKeySpec;
+import java.security.InvalidKeyException;
+import java.security.NoSuchAlgorithmException;
+import java.security.cert.Certificate;
+
+public class Encryptor {
+
+    public byte[] encryptMessage(byte[] message, byte[] keyBytes) throws InvalidKeyException, NoSuchPaddingException, NoSuchAlgorithmException, BadPaddingException, IllegalBlockSizeException {
+        Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
+        SecretKey secretKey = new SecretKeySpec(keyBytes, "AES");
+        cipher.init(Cipher.ENCRYPT_MODE, secretKey);
+        byte[] encryptedMessage = cipher.doFinal(message);
+        return encryptedMessage;
+    }
+
+    public byte[] encryptMessage(byte[] message, Certificate publicKeyCertificate) throws InvalidKeyException, NoSuchPaddingException, NoSuchAlgorithmException, BadPaddingException, IllegalBlockSizeException {
+        Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
+        cipher.init(Cipher.ENCRYPT_MODE, publicKeyCertificate);
+        byte[] encryptedMessage = cipher.doFinal(message);
+        return encryptedMessage;
+    }
+
+    public byte[] decryptMessage(byte[] encryptedMessage, byte[] keyBytes) throws NoSuchPaddingException, NoSuchAlgorithmException, InvalidKeyException, BadPaddingException, IllegalBlockSizeException {
+        Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
+        SecretKey secretKey = new SecretKeySpec(keyBytes, "AES");
+        cipher.init(Cipher.DECRYPT_MODE, secretKey);
+        byte[] clearMessage = cipher.doFinal(encryptedMessage);
+        return clearMessage;
+    }
+
+
+}

core-java/src/test/java/com/baeldung/cipher/EncryptorUnitTest.java

@@ -0,0 +1,70 @@
+package com.baeldung.cipher;
+
+
+import org.junit.Before;
+import org.junit.Test;
+
+import java.io.ByteArrayInputStream;
+import java.io.InputStream;
+import java.security.cert.CertificateFactory;
+import java.security.cert.X509Certificate;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class EncryptorUnitTest {
+    private String encKeyString;
+    private String message;
+    private String  certificateString;
+    private Encryptor encryptor;
+
+    @Before
+    public void init(){
+        encKeyString =  "1234567890123456";
+        message = "This is a secret message";
+        encryptor =  new Encryptor();
+        certificateString = "-----BEGIN CERTIFICATE-----\n" +
+                "MIICVjCCAb8CAg37MA0GCSqGSIb3DQEBBQUAMIGbMQswCQYDVQQGEwJKUDEOMAwG\n" +
+                "A1UECBMFVG9reW8xEDAOBgNVBAcTB0NodW8ta3UxETAPBgNVBAoTCEZyYW5rNERE\n" +
+                "MRgwFgYDVQQLEw9XZWJDZXJ0IFN1cHBvcnQxGDAWBgNVBAMTD0ZyYW5rNEREIFdl\n" +
+                "YiBDQTEjMCEGCSqGSIb3DQEJARYUc3VwcG9ydEBmcmFuazRkZC5jb20wHhcNMTIw\n" +
+                "ODIyMDUyNzIzWhcNMTcwODIxMDUyNzIzWjBKMQswCQYDVQQGEwJKUDEOMAwGA1UE\n" +
+                "CAwFVG9reW8xETAPBgNVBAoMCEZyYW5rNEREMRgwFgYDVQQDDA93d3cuZXhhbXBs\n" +
+                "ZS5jb20wgZ8wDQYJKoZIhvcNAQEBBQADgY0AMIGJAoGBAMYBBrx5PlP0WNI/ZdzD\n" +
+                "+6Pktmurn+F2kQYbtc7XQh8/LTBvCo+P6iZoLEmUA9e7EXLRxgU1CVqeAi7QcAn9\n" +
+                "MwBlc8ksFJHB0rtf9pmf8Oza9E0Bynlq/4/Kb1x+d+AyhL7oK9tQwB24uHOueHi1\n" +
+                "C/iVv8CSWKiYe6hzN1txYe8rAgMBAAEwDQYJKoZIhvcNAQEFBQADgYEAASPdjigJ\n" +
+                "kXCqKWpnZ/Oc75EUcMi6HztaW8abUMlYXPIgkV2F7YanHOB7K4f7OOLjiz8DTPFf\n" +
+                "jC9UeuErhaA/zzWi8ewMTFZW/WshOrm3fNvcMrMLKtH534JKvcdMg6qIdjTFINIr\n" +
+                "evnAhf0cwULaebn+lMs8Pdl7y37+sfluVok=\n" +
+                "-----END CERTIFICATE-----";
+    }
+
+    @Test
+    public void givenEncryptionKey_whenMessageIsPassedToEncryptor_thenMessageIsEncrypted() throws Exception {
+        byte[] encryptedMessage = encryptor.encryptMessage(message.getBytes(),encKeyString.getBytes());
+
+        assertThat(encryptedMessage).isNotNull();
+        assertThat(encryptedMessage.length  % 32).isEqualTo(0);
+    }
+
+    @Test
+    public void givenCertificateWithPublicKey_whenMessageIsPassedToEncryptor_thenMessageIsEncrypted() throws Exception {
+        CertificateFactory factory = CertificateFactory.getInstance("X.509");
+        InputStream is = new ByteArrayInputStream(certificateString.getBytes());
+        X509Certificate certificate = (X509Certificate) factory.generateCertificate(is);
+
+        byte[] encryptedMessage = encryptor.encryptMessage(message.getBytes(),certificate);
+
+        assertThat(encryptedMessage).isNotNull();
+        assertThat(encryptedMessage.length  % 128).isEqualTo(0);
+    }
+
+    @Test
+    public void givenEncryptionKey_whenMessageIsEncrypted_thenDecryptMessage() throws Exception{
+        byte[] encryptedMessageBytes = encryptor.encryptMessage(message.getBytes(),encKeyString.getBytes());
+
+        byte[] clearMessageBytes = encryptor.decryptMessage(encryptedMessageBytes, encKeyString.getBytes());
+
+        assertThat(message).isEqualTo(new String(clearMessageBytes));
+    }
+}