#BAEL-6958: add KemUtils main source

Author: hmdrzsharifi

core-java-modules/core-java-security-5/src/main/java/com/baeldung/kem/KemUtils.java

@@ -0,0 +1,27 @@
+package com.baeldung.kem;
+
+import java.security.PrivateKey;
+import java.security.PublicKey;
+
+import javax.crypto.KEM;
+import javax.crypto.SecretKey;
+
+public class KemUtils {
+
+    public record KemResult(SecretKey sharedSecret, byte[] encapsulation) {}
+
+    public static KemResult encapsulate(String algorithm, PublicKey publicKey) throws Exception {
+        KEM kem = KEM.getInstance(algorithm);
+        KEM.Encapsulator encapsulator = kem.newEncapsulator(publicKey);
+        KEM.Encapsulated result = encapsulator.encapsulate();
+        return new KemResult(result.key(), result.encapsulation());
+    }
+
+    public static KemResult decapsulate(String algorithm, PrivateKey privateKey, byte[] encapsulation) throws Exception {
+        KEM kem = KEM.getInstance(algorithm);
+        KEM.Decapsulator decapsulator = kem.newDecapsulator(privateKey);
+        SecretKey recoveredSecret = decapsulator.decapsulate(encapsulation);
+        return new KemResult(recoveredSecret, encapsulation);
+    }
+
+}