create package-private AESCipherCBCnoPad, update documentation

DEVSIX-8933

Author: Alexandr Pliushchou

kernel/src/main/java/com/itextpdf/kernel/crypto/AESCipherCBCnoPad.java

@@ -34,7 +34,13 @@ This file is part of the iText (R) project.
 
 /**
  * Creates an AES Cipher with CBC and no padding.
+ * @deprecated the AES-CBC cipher is a low-level cryptographic primitive
+ * that requires careful understanding to use it safely.
+ * This class is only a thin wrapper and is not intended for general use.
+ * Instead, use API provided by cryptography libraries directly
+ * or rely on high-level PDF encryption functionality.
  */
+@Deprecated
 public class AESCipherCBCnoPad {
 
     private static final String CIPHER_WITHOUT_PADDING = "AES/CBC/NoPadding";

kernel/src/main/java/com/itextpdf/kernel/crypto/securityhandler/AESCipherCBCnoPad.java

@@ -0,0 +1,58 @@
+/*
+    This file is part of the iText (R) project.
+    Copyright (c) 1998-2025 Apryse Group NV
+    Authors: Apryse Software.
+
+    This program is offered under a commercial and under the AGPL license.
+    For commercial licensing, contact us at https://itextpdf.com/sales.  For AGPL licensing, see below.
+
+    AGPL licensing:
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Affero General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU Affero General Public License for more details.
+
+    You should have received a copy of the GNU Affero General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+package com.itextpdf.kernel.crypto.securityhandler;
+
+/**
+ * Creates an AES Cipher with CBC and no padding.
+ */
+class AESCipherCBCnoPad {
+
+    com.itextpdf.kernel.crypto.AESCipherCBCnoPad aESCipherCBCnoPad;
+
+    /**
+     * Creates a new instance of AESCipher with CBC and no padding
+     *
+     * @param forEncryption if true the cipher is initialised for
+     *                      encryption, if false for decryption
+     * @param key           the key to be used in the cipher
+     */
+    AESCipherCBCnoPad(boolean forEncryption, byte[] key) {
+        aESCipherCBCnoPad = new com.itextpdf.kernel.crypto.AESCipherCBCnoPad(forEncryption, key);
+    }
+
+    /**
+     * Creates a new instance of AESCipher with CBC and no padding
+     *
+     * @param forEncryption if true the cipher is initialised for
+     *                      encryption, if false for decryption
+     * @param key           the key to be used in the cipher
+     * @param initVector    initialization vector to be used in cipher
+     */
+    AESCipherCBCnoPad(boolean forEncryption, byte[] key, byte[] initVector) {
+        aESCipherCBCnoPad = new com.itextpdf.kernel.crypto.AESCipherCBCnoPad(forEncryption, key, initVector);
+    }
+
+    byte[] processBlock(byte[] inp, int inpOff, int inpLen) {
+        return aESCipherCBCnoPad.processBlock(inp, inpOff, inpLen);
+    }
+}

kernel/src/main/java/com/itextpdf/kernel/crypto/securityhandler/StandardHandlerUsingAes256.java

@@ -25,7 +25,6 @@ This file is part of the iText (R) project.
 import com.itextpdf.io.logs.IoLogMessageConstant;
 import com.itextpdf.io.util.StreamUtil;
 import com.itextpdf.kernel.exceptions.PdfException;
-import com.itextpdf.kernel.crypto.AESCipherCBCnoPad;
 import com.itextpdf.kernel.crypto.AesDecryptor;
 import com.itextpdf.kernel.exceptions.BadPasswordException;
 import com.itextpdf.kernel.crypto.IDecryptor;