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();
    }

        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);

        }

        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);

        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;
    }

        final int start = dstIndex;

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

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

        writeInt2(fid, dst, dstIndex);
        dstIndex += 2;
        writeInt4(offset, dst, dstIndex);
        dstIndex += 4;

        final int i = inData[inIndex] & 0xff;
        outData[outIndex] = ENCODE_TABLE[i >> 2];
        outData[outIndex + 1] = ENCODE_TABLE[i << 4 & 0x3f];
        outData[outIndex + 2] = PAD;
        outData[outIndex + 3] = PAD;
    }

    private static void encode1pad(final byte[] inData, final int inIndex, final char[] outData, final int outIndex) {

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     */
    public Smb2TransformHeader(final byte[] nonce, final int originalMessageSize, final int flags, final long sessionId) {
        if (nonce.length == 12) {
            // For CCM cipher, pad nonce to 16 bytes with zeros
            System.arraycopy(nonce, 0, this.nonce, 0, 12);
            // Last 4 bytes remain zero-initialized
        } else if (nonce.length == 16) {

        // Context handle (20 bytes) - this is both input and output (modified)
        if (contextHandle != null) {
            buf.writeOctetArray(contextHandle, 0, Math.min(contextHandle.length, 20));
            // Pad with zeros if context handle is shorter than 20 bytes
            for (int i = contextHandle.length; i < 20; i++) {
                buf.enc_ndr_small(0);
            }
        } else {