hw/ip/aes/rtl/aes_sbox.sv

// Copyright lowRISC contributors.
// Licensed under the Apache License, Version 2.0, see LICENSE for details.
// SPDX-License-Identifier: Apache-2.0
//
// AES SBox

`include "prim_assert.sv"

module aes_sbox import aes_pkg::*;
#(
  parameter sbox_impl_e SecSBoxImpl = SBoxImplLut
) (
  input  logic                     clk_i,
  input  logic                     rst_ni,
  input  logic                     en_i,
  output logic                     out_req_o,
  input  logic                     out_ack_i,
  input  ciph_op_e                 op_i,
  input  logic               [7:0] data_i,
  input  logic               [7:0] mask_i,
  input  logic [WidthPRDSBox+19:0] prd_i,
  output logic               [7:0] data_o,
  output logic               [7:0] mask_o,
  output logic              [19:0] prd_o
);

  // Create a lint error to reduce the risk of accidentally using a less secure SBox
  // implementation.
  `ASSERT_STATIC_LINT_ERROR(AesSBoxSecSBoxImplNonDefault, SecSBoxImpl == SBoxImplDom)

  localparam bit SBoxMasked = (SecSBoxImpl == SBoxImplCanrightMasked ||
                               SecSBoxImpl == SBoxImplCanrightMaskedNoreuse ||
                               SecSBoxImpl == SBoxImplDom) ? 1'b1 : 1'b0;

  localparam bit SBoxSingleCycle = (SecSBoxImpl == SBoxImplDom) ? 1'b0 : 1'b1;

  if (!SBoxMasked) begin : gen_sbox_unmasked
    // Tie off unused inputs.
    logic                     unused_clk;
    logic                     unused_rst;
    logic               [7:0] unused_mask;
    logic [WidthPRDSBox+19:0] unused_prd;
    assign unused_clk  = clk_i;
    assign unused_rst  = rst_ni;
    assign unused_mask = mask_i;
    assign unused_prd  = prd_i;

    if (SecSBoxImpl == SBoxImplCanright) begin : gen_sbox_canright
      aes_sbox_canright u_aes_sbox (
        .op_i   ( op_i   ),
        .data_i ( data_i ),
        .data_o ( data_o )
      );

    end else begin : gen_sbox_lut // SecSBoxImpl == SBoxImplLut
      aes_sbox_lut u_aes_sbox (
        .op_i   ( op_i   ),
        .data_i ( data_i ),
        .data_o ( data_o )
      );
    end

    assign mask_o = '0;
    assign prd_o  = '0;

  end else begin : gen_sbox_masked

    // SEC_CM: KEY.MASKING
    if (SecSBoxImpl == SBoxImplDom) begin : gen_sbox_dom

      aes_sbox_dom u_aes_sbox (
        .clk_i      ( clk_i       ),
        .rst_ni     ( rst_ni      ),
        .en_i       ( en_i        ),
        .out_req_o  ( out_req_o   ),
        .out_ack_i  ( out_ack_i   ),
        .op_i       ( op_i        ),
        .data_i     ( data_i      ),
        .mask_i     ( mask_i      ),
        .prd_i      ( prd_i[27:0] ),
        .data_o     ( data_o      ),
        .mask_o     ( mask_o      ),
        .prd_o      ( prd_o       )
      );

      `ASSERT_INIT(AesWidthPRDSBox, WidthPRDSBox == 8)

    end else if (SecSBoxImpl == SBoxImplCanrightMaskedNoreuse) begin :
        gen_sbox_canright_masked_noreuse
      // Tie off unused inputs.
      logic        unused_clk;
      logic        unused_rst;
      logic [19:0] unused_prd;
      assign unused_clk = clk_i;
      assign unused_rst = rst_ni;
      assign unused_prd = prd_i[WidthPRDSBox+19:WidthPRDSBox];

      aes_sbox_canright_masked_noreuse u_aes_sbox (
        .op_i   ( op_i        ),
        .data_i ( data_i      ),
        .mask_i ( mask_i      ),
        .prd_i  ( prd_i[17:0] ),
        .data_o ( data_o      ),
        .mask_o ( mask_o      )
      );

      assign prd_o = '0;

      `ASSERT_INIT(AesWidthPRDSBox, WidthPRDSBox == 18)

    end else begin : gen_sbox_canright_masked // SecSBoxImpl == SBoxImplCanrightMasked
      // Tie off unused inputs.
      logic        unused_clk;
      logic        unused_rst;
      logic [19:0] unused_prd;
      assign unused_clk = clk_i;
      assign unused_rst = rst_ni;
      assign unused_prd = prd_i[WidthPRDSBox+19:WidthPRDSBox];

      aes_sbox_canright_masked u_aes_sbox (
        .op_i   ( op_i       ),
        .data_i ( data_i     ),
        .mask_i ( mask_i     ),
        .prd_i  ( prd_i[7:0] ),
        .data_o ( data_o     ),
        .mask_o ( mask_o     )
      );

      assign prd_o = '0;

      `ASSERT_INIT(AesWidthPRDSBox, WidthPRDSBox == 8)
    end
  end

  if (SBoxSingleCycle) begin : gen_req_singlecycle
    // Tie off unused inputs.
    logic unused_out_ack;
    assign unused_out_ack = out_ack_i;

    // Signal that we have valid output right away.
    assign out_req_o = en_i;
  end

endmodule