585 simon_cipher
585 : simon_cipher
- Author: Simon Cipher
- Description: Bitserial implementation of Simon-128
- GitHub repository
- Clock: 0 Hz
How it works
This is a bitserial implementation of the SIMON Block Cipher. SIMON is a 128-bit block cipher, see The SIMON and SPECK families of Lightweight Block Ciphers. A bit-serial implementation exchanges throughput for area, thereby creating a compact cipher that is dominated by flip-flops and multiplexer cells. However, the overal design size becomes minimal. A detailed description of the bitserial implementation technique for SIMON is available in SIMON Says, Break the Area Records for Symmetric Key Block Ciphers on FPGAs .
| Cell | Count |
|---|---|
| flip-flop | 281 |
| mux | 588 |
| other logic | 199 |
| TOTAL | 1068 |
The design uses a 3-bit input and a 2-bit output, in addition to clock and reset.
| Port | Function |
|---|---|
| ui[0] | Bitserial Data Input |
| ui[7:6] | Control Word |
| uo[0] | Bitserial Data Output |
| uo[7] | Data Output Valid |
The data input is asserted by the control word, and must be valid when the control word indicates a plaintext-loading or key-loading operation.
The data output is asserted by the valid bit, and should be ignored when the data valid bit is 0. The output ciphertext is produced in 128 consecutive clock cycles.
The 2-bit control word defines the operation of the cipher. The LSB is a debug bit study to key-loading process and to verify that the key register was correctly loaded.
| Control | Function |
|---|---|
| 00 | Idle |
| 01 | Load 128-bit plaintext |
| 10 | Load 128-bit key (see LIMITATIONS) |
| 11 | Encrypt and return ciphertext |
LIMITATIONS
This design forces the key bits to 0 upon loading, so that the effective key value of the cipher is always hardcoded to 00000000_00000000_00000000_00000000. This disables the use of the design as a cipher, yet it still demonstrates how a bit-serial architecture can be designed.
How to test
Study the testbench for example test vectors.
External hardware
No external hardware is needed for this project.
IO
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | ui_in[0] | uo_out[0] | |
| 1 | ui_in[1] | uo_out[1] | |
| 2 | ui_in[2] | uo_out[2] | |
| 3 | ui_in[3] | uo_out[3] | |
| 4 | ui_in[4] | uo_out[4] | |
| 5 | ui_in[5] | uo_out[5] | |
| 6 | ui_in[6] | uo_out[6] | |
| 7 | ui_in[7] | uo_out[7] |