[KTLN-816] Add Samples (#808)

Author: LeoColman

core-kotlin-modules/core-kotlin-10/src/main/kotlin/com/baeldung/aes/EncryptionDecryption.kt

@@ -0,0 +1,26 @@
+package com.baeldung.aes
+
+import javax.crypto.Cipher
+import javax.crypto.KeyGenerator
+import javax.crypto.SecretKey
+import javax.crypto.spec.IvParameterSpec
+
+fun generateAESKey(keySize: Int = 256): SecretKey {
+    val keyGenerator = KeyGenerator.getInstance("AES")
+    keyGenerator.init(keySize)
+    return keyGenerator.generateKey()
+}
+
+fun aesEncrypt(data: ByteArray, secretKey: SecretKey): ByteArray {
+    val cipher = Cipher.getInstance("AES/CBC/PKCS5Padding")
+    val ivParameterSpec = IvParameterSpec(ByteArray(16)) // Use a secure IV in production
+    cipher.init(Cipher.ENCRYPT_MODE, secretKey, ivParameterSpec)
+    return cipher.doFinal(data)
+}
+
+fun aesDecrypt(encryptedData: ByteArray, secretKey: SecretKey): ByteArray {
+    val cipher = Cipher.getInstance("AES/CBC/PKCS5Padding")
+    val ivParameterSpec = IvParameterSpec(ByteArray(16)) // Use the same IV as used in encryption
+    cipher.init(Cipher.DECRYPT_MODE, secretKey, ivParameterSpec)
+    return cipher.doFinal(encryptedData)
+}

core-kotlin-modules/core-kotlin-10/src/test/kotlin/com/baeldung/aes/EncryptionDecryptionUnitTest.kt

@@ -0,0 +1,18 @@
+package com.baeldung.aes
+
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+
+class EncryptionDecryptionUnitTest {
+    @Test
+    fun `Given text when encrypted and decrypted should return original text`() {
+        val originalText = "Hello Kotlin AES Encryption!"
+        val secretKey = generateAESKey(256)
+
+        val encryptedData = aesEncrypt(originalText.toByteArray(), secretKey)
+        val decryptedData = aesDecrypt(encryptedData, secretKey)
+        val decryptedText = String(decryptedData)
+
+        assertEquals(originalText, decryptedText, "The decrypted text does not match the original")
+    }
+}