byte[] ipad = new byte[64];
        byte[] opad = new byte[64];

        for (int i = 0; i < key.length; i++) {
            ipad[i] = (byte) (key[i] ^ 0x36);
            opad[i] = (byte) (key[i] ^ 0x5c);
        }
        for (int i = key.length; i < 64; i++) {
            ipad[i] = 0x36;
            opad[i] = 0x5c;
        }

        md5.update(ipad);

        final int length = Math.min(key.length, BLOCK_LENGTH);
        for (int i = 0; i < length; i++) {
            ipad[i] = (byte) (key[i] ^ IPAD);
            opad[i] = (byte) (key[i] ^ OPAD);
        }
        for (int i = length; i < BLOCK_LENGTH; i++) {
            ipad[i] = IPAD;
            opad[i] = OPAD;
        }
        try {
            md5 = MessageDigest.getInstance("MD5");
        } catch (final Exception ex) {

        final int length = Math.min(key.length, BLOCK_LENGTH);
        for (int i = 0; i < length; i++) {
            this.ipad[i] = (byte) (key[i] ^ IPAD);
            this.opad[i] = (byte) (key[i] ^ OPAD);
        }
        for (int i = length; i < BLOCK_LENGTH; i++) {
            this.ipad[i] = IPAD;
            this.opad[i] = OPAD;
        }

        this.md5 = Crypto.getMD5();
        engineReset();
    }

        MessageDigest md5 = MessageDigest.getInstance("MD5");
        byte[] ipad = new byte[64];
        byte[] opad = new byte[64];

        // HMACT64 specific: truncate key to 64 bytes if needed
        int keyLen = Math.min(key.length, 64);
        for (int i = 0; i < keyLen; i++) {
            ipad[i] = (byte) (key[i] ^ 0x36);
            opad[i] = (byte) (key[i] ^ 0x5c);
        }
        for (int i = keyLen; i < 64; i++) {

        final int start = dstIndex;

        this.dataOffset = dstIndex - this.headerStart + 26; // 26 = off from here to pad

        this.pad = (this.dataOffset - this.headerStart) % 4;
        this.pad = this.pad == 0 ? 0 : 4 - this.pad;
        this.dataOffset += this.pad;

        SMBUtil.writeInt2(this.fid, dst, dstIndex);
        dstIndex += 2;
        SMBUtil.writeInt4(this.offset, dst, dstIndex);

    @Test
    @DisplayName("Test pad calculation with various offsets")
    void testPadCalculation() {
        // Test pad calculation with different alignment values
        assertEquals(0, transaction.pad(0)); // Already aligned
        assertEquals(0, transaction.pad(4)); // Already aligned
        assertEquals(0, transaction.pad(8)); // Already aligned
        assertEquals(3, transaction.pad(1)); // Need 3 bytes to align to 4

                pad = parameterOffset % PADDING_SIZE;
                pad = pad == 0 ? 0 : PADDING_SIZE - pad;
                parameterOffset += pad;
            }

            // caclulate parameterDisplacement before calculating new parameterCount
            parameterDisplacement += parameterCount;

            int available = maxBufferSize - parameterOffset - pad;

        }

        return bufferIndex - start;
    }

    @Override
    int readBytesWireFormat(final byte[] buffer, int bufferIndex) {
        pad = pad1 = 0;
        final int n;

        if (parameterCount > 0) {
            bufferIndex += pad = parameterOffset - (bufferIndex - headerStart);
            System.arraycopy(buffer, bufferIndex, txn_buf, bufParameterStart + parameterDisplacement, parameterCount);

    }

    @Override
    protected int readBytesWireFormat(final byte[] buffer, int bufferIndex) throws SMBProtocolDecodingException {
        this.pad = this.pad1 = 0;
        if (this.parameterCount > 0) {
            bufferIndex += this.pad = this.parameterOffset - (bufferIndex - this.headerStart);

        bufferIndex += 4;

        final int pad = bufferIndex - (getHeaderStart() + securityBufferOffset);
        this.blob = new byte[securityBufferLength];
        System.arraycopy(buffer, getHeaderStart() + securityBufferOffset, this.blob, 0, securityBufferLength);
        bufferIndex += pad;
        bufferIndex += securityBufferLength;

        return bufferIndex - start;
    }