Materi DES tambahan
Kotak substitusi (Kotak-S)

| S1 | x0000x | x0001x | x0010x | x0011x | x0100x | x0101x | x0110x | x0111x | x1000x | x1001x | x1010x | x1011x | x1100x | x1101x | x1110x | x1111x |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 0yyyy0 | 14 | 4 | 13 | 1 | 2 | 15 | 11 | 8 | 3 | 10 | 6 | 12 | 5 | 9 | 0 | 7 |
| 0yyyy1 | 0 | 15 | 7 | 4 | 14 | 2 | 13 | 1 | 10 | 6 | 12 | 11 | 9 | 5 | 3 | 8 |
| 1yyyy0 | 4 | 1 | 14 | 8 | 13 | 6 | 2 | 11 | 15 | 12 | 9 | 7 | 3 | 10 | 5 | 0 |
| 1yyyy1 | 15 | 12 | 8 | 2 | 4 | 9 | 1 | 7 | 5 | 11 | 3 | 14 | 10 | 0 | 6 | 13 |

| S2 | x0000x | x0001x | x0010x | x0011x | x0100x | x0101x | x0110x | x0111x | x1000x | x1001x | x1010x | x1011x | x1100x | x1101x | x1110x | x1111x |
| 0yyyy0 | 15 | 1 | 8 | 14 | 6 | 11 | 3 | 4 | 9 | 7 | 2 | 13 | 12 | 0 | 5 | 10 |
| 0yyyy1 | 3 | 13 | 4 | 7 | 15 | 2 | 8 | 14 | 12 | 0 | 1 | 10 | 6 | 9 | 11 | 5 |
| 1yyyy0 | 0 | 14 | 7 | 11 | 10 | 4 | 13 | 1 | 5 | 8 | 12 | 6 | 9 | 3 | 2 | 15 |
| 1yyyy1 | 13 | 8 | 10 | 1 | 3 | 15 | 4 | 2 | 11 | 6 | 7 | 12 | 0 | 5 | 14 | 9 |

| S3 | x0000x | x0001x | x0010x | x0011x | x0100x | x0101x | x0110x | x0111x | x1000x | x1001x | x1010x | x1011x | x1100x | x1101x | x1110x | x1111x |
| 0yyyy0 | 10 | 0 | 9 | 14 | 6 | 3 | 15 | 5 | 1 | 13 | 12 | 7 | 11 | 4 | 2 | 8 |
| 0yyyy1 | 13 | 7 | 0 | 9 | 3 | 4 | 6 | 10 | 2 | 8 | 5 | 14 | 12 | 11 | 15 | 1 |
| 1yyyy0 | 13 | 6 | 4 | 9 | 8 | 15 | 3 | 0 | 11 | 1 | 2 | 12 | 5 | 10 | 14 | 7 |
| 1yyyy1 | 1 | 10 | 13 | 0 | 6 | 9 | 8 | 7 | 4 | 15 | 14 | 3 | 11 | 5 | 2 | 12 |

| S4 | x0000x | x0001x | x0010x | x0011x | x0100x | x0101x | x0110x | x0111x | x1000x | x1001x | x1010x | x1011x | x1100x | x1101x | x1110x | x1111x |
| 0yyyy0 | 7 | 13 | 14 | 3 | 0 | 6 | 9 | 10 | 1 | 2 | 8 | 5 | 11 | 12 | 4 | 15 |
| 0yyyy1 | 13 | 8 | 11 | 5 | 6 | 15 | 0 | 3 | 4 | 7 | 2 | 12 | 1 | 10 | 14 | 9 |
| 1yyyy0 | 10 | 6 | 9 | 0 | 12 | 11 | 7 | 13 | 15 | 1 | 3 | 14 | 5 | 2 | 8 | 4 |
| 1yyyy1 | 3 | 15 | 0 | 6 | 10 | 1 | 13 | 8 | 9 | 4 | 5 | 11 | 12 | 7 | 2 | 14 |

| S5 | x0000x | x0001x | x0010x | x0011x | x0100x | x0101x | x0110x | x0111x | x1000x | x1001x | x1010x | x1011x | x1100x | x1101x | x1110x | x1111x |
| 0yyyy0 | 2 | 12 | 4 | 1 | 7 | 10 | 11 | 6 | 8 | 5 | 3 | 15 | 13 | 0 | 14 | 9 |
| 0yyyy1 | 14 | 11 | 2 | 12 | 4 | 7 | 13 | 1 | 5 | 0 | 15 | 10 | 3 | 9 | 8 | 6 |
| 1yyyy0 | 4 | 2 | 1 | 11 | 10 | 13 | 7 | 8 | 15 | 9 | 12 | 5 | 6 | 3 | 0 | 14 |
| 1yyyy1 | 11 | 8 | 12 | 7 | 1 | 14 | 2 | 13 | 6 | 15 | 0 | 9 | 10 | 4 | 5 | 3 |

| S6 | x0000x | x0001x | x0010x | x0011x | x0100x | x0101x | x0110x | x0111x | x1000x | x1001x | x1010x | x1011x | x1100x | x1101x | x1110x | x1111x |
| 0yyyy0 | 12 | 1 | 10 | 15 | 9 | 2 | 6 | 8 | 0 | 13 | 3 | 4 | 14 | 7 | 5 | 11 |
| 0yyyy1 | 10 | 15 | 4 | 2 | 7 | 12 | 9 | 5 | 6 | 1 | 13 | 14 | 0 | 11 | 3 | 8 |
| 1yyyy0 | 9 | 14 | 15 | 5 | 2 | 8 | 12 | 3 | 7 | 0 | 4 | 10 | 1 | 13 | 11 | 6 |
| 1yyyy1 | 4 | 3 | 2 | 12 | 9 | 5 | 15 | 10 | 11 | 14 | 1 | 7 | 6 | 0 | 8 | 13 |

| S7 | x0000x | x0001x | x0010x | x0011x | x0100x | x0101x | x0110x | x0111x | x1000x | x1001x | x1010x | x1011x | x1100x | x1101x | x1110x | x1111x |
| 0yyyy0 | 4 | 11 | 2 | 14 | 15 | 0 | 8 | 13 | 3 | 12 | 9 | 7 | 5 | 10 | 6 | 1 |
| 0yyyy1 | 13 | 0 | 11 | 7 | 4 | 9 | 1 | 10 | 14 | 3 | 5 | 12 | 2 | 15 | 8 | 6 |
| 1yyyy0 | 1 | 4 | 11 | 13 | 12 | 3 | 7 | 14 | 10 | 15 | 6 | 8 | 0 | 5 | 9 | 2 |
| 1yyyy1 | 6 | 11 | 13 | 8 | 1 | 4 | 10 | 7 | 9 | 5 | 0 | 15 | 14 | 2 | 3 | 12 |

| S8 | x0000x | x0001x | x0010x | x0011x | x0100x | x0101x | x0110x | x0111x | x1000x | x1001x | x1010x | x1011x | x1100x | x1101x | x1110x | x1111x |
| 0yyyy0 | 13 | 2 | 8 | 4 | 6 | 15 | 11 | 1 | 10 | 9 | 3 | 14 | 5 | 0 | 12 | 7 |
| 0yyyy1 | 1 | 15 | 13 | 8 | 10 | 3 | 7 | 4 | 12 | 5 | 6 | 11 | 0 | 14 | 9 | 2 |
| 1yyyy0 | 7 | 11 | 4 | 1 | 9 | 12 | 14 | 2 | 0 | 6 | 10 | 13 | 15 | 3 | 5 | 8 |
| 1yyyy1 | 2 | 1 | 14 | 7 | 4 | 10 | 8 | 13 | 15 | 12 | 9 | 0 | 3 | 5 | 6 | 11 |
Tabel ini mendaftar delapan kotak-S yang dipakai dalam DES. Tiap kotak-S mengganti masukan 6 bit ke keluaran 4 bit. Bila diberikan masukan 6 bit, keluarannya ditentukan dengan memilih baris dari bit-bit terluar dan memilih kolom dari empat bit tengah. Misalnya, masukan 011011 memiliki bit-bit terluar "01" dan empat bit tengah 1101 sehingga S5(011011) adalah 1001. (Lihat kotak-S).