Code commit for BAEL-4489 (#10790)

* Code commit for "Converting String to BigDecimal in Java" - Article

* modified the assert param for comparing actual and expected values

* removed the conflict change

* Code commit for Secret Key to String and vice versa in java

* renaming the junit class name to match coding standard

core-java-modules/core-java-security-2/src/main/java/com/baeldung/secretkeyandstringconversion/ConversionClassUtil.java

@@ -0,0 +1,53 @@
+package com.baeldung.secretkeyandstringconversion;
+
+import java.security.NoSuchAlgorithmException;
+import java.security.spec.InvalidKeySpecException;
+import java.security.spec.KeySpec;
+import java.util.Base64;
+
+import javax.crypto.KeyGenerator;
+import javax.crypto.SecretKey;
+import javax.crypto.SecretKeyFactory;
+import javax.crypto.spec.PBEKeySpec;
+import javax.crypto.spec.SecretKeySpec;
+
+public class ConversionClassUtil {
+
+	/* Generating Secret key */
+
+	// Generating Secret Key using KeyGenerator class with 256
+	public static SecretKey generateKey(int n) throws NoSuchAlgorithmException {
+		KeyGenerator keyGenerator = KeyGenerator.getInstance("AES");
+		keyGenerator.init(n);
+		SecretKey originalKey = keyGenerator.generateKey();
+		return originalKey;
+	}
+
+	// Generating Secret Key using password and salt
+	public static SecretKey getKeyFromPassword(String password, String salt)
+			throws NoSuchAlgorithmException, InvalidKeySpecException {
+		SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA256");
+		KeySpec spec = new PBEKeySpec(password.toCharArray(), salt.getBytes(), 65536, 256);
+		SecretKey originalKey = new SecretKeySpec(factory.generateSecret(spec).getEncoded(), "AES");
+		return originalKey;
+	}
+
+	/* Converting Secret key into String */
+	public static String convertSecretKeyToString(SecretKey secretKey) throws NoSuchAlgorithmException {
+		// Converting the Secret Key into byte array
+		byte[] rawData = secretKey.getEncoded();
+		// Getting String - Base64 encoded version of the Secret Key
+		String encodedKey = Base64.getEncoder().encodeToString(rawData);
+		return encodedKey;
+	}
+
+	/* Converting String into Secret key into */
+	public static SecretKey convertStringToSecretKeyto(String encodedKey) {
+		// Decoding the Base64 encoded string into byte array
+		byte[] decodedKey = Base64.getDecoder().decode(encodedKey);
+		// Rebuilding the Secret Key using SecretKeySpec Class
+		SecretKey originalKey = new SecretKeySpec(decodedKey, 0, decodedKey.length, "AES");
+		return originalKey;
+	}
+
+}

core-java-modules/core-java-security-2/src/test/java/com/baeldung/secretkeyandstringconversion/ConversionClassUtilUnitTest.java

@@ -0,0 +1,44 @@
+package com.baeldung.secretkeyandstringconversion;
+
+import java.security.NoSuchAlgorithmException;
+import java.security.spec.InvalidKeySpecException;
+
+import javax.crypto.SecretKey;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class ConversionClassUtilUnitTest {
+
+	@Test
+	void givenPasswordAndSalt_whenCreateSecreKeyCheckConversion_thenSuccess()
+			throws NoSuchAlgorithmException, InvalidKeySpecException {
+		// given
+		String password = "Baeldung@2021";
+		String salt = "@$#baelDunG@#^$*";
+
+		// when
+		SecretKey encodedKey = ConversionClassUtil.getKeyFromPassword(password, salt);
+		String encodedString = ConversionClassUtil.convertSecretKeyToString(encodedKey);
+		SecretKey decodeKey = ConversionClassUtil.convertStringToSecretKeyto(encodedString);
+
+		// then
+		Assertions.assertEquals(encodedKey, decodeKey);
+	}
+
+	@Test
+	void givenSize_whenCreateSecreKeyCheckConversion_thenSuccess()
+			throws NoSuchAlgorithmException, InvalidKeySpecException {
+		// given
+		int size = 256;
+
+		// when
+		SecretKey encodedKey = ConversionClassUtil.generateKey(size);
+		String encodedString = ConversionClassUtil.convertSecretKeyToString(encodedKey);
+		SecretKey decodeKey = ConversionClassUtil.convertStringToSecretKeyto(encodedString);
+
+		// then
+		Assertions.assertEquals(encodedKey, decodeKey);
+	}
+
+}