https://github.com/danielost/sp-box
S-box/p-box implementation
https://github.com/danielost/sp-box
block-ciphers cryptography p-box s-box
Last synced: 11 days ago
JSON representation
S-box/p-box implementation
- Host: GitHub
- URL: https://github.com/danielost/sp-box
- Owner: danielost
- Created: 2023-10-24T18:07:28.000Z (over 1 year ago)
- Default Branch: main
- Last Pushed: 2023-10-25T12:13:13.000Z (over 1 year ago)
- Last Synced: 2025-02-16T19:48:51.228Z (3 months ago)
- Topics: block-ciphers, cryptography, p-box, s-box
- Language: Go
- Homepage:
- Size: 6.84 KB
- Stars: 0
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
Awesome Lists containing this project
README
# S-box and P-box
This is an implementation of functions for forward and reverse conversion using the S-box algorithm as well as the P-box algorithm.
## Work done
`src/sbox/` - S-box implementation
`src/pbox/` - P-box implementation
`tests/` - tests for the functions
## Using the S-box
This implementation uses an S-box from the [AES (Rijndael)](https://en.wikipedia.org/wiki/Advanced_Encryption_Standard).
The `src/sbox` package has two public functions:
1. `Lookup(uint8) uint8` - to substitute the value using the s-box.
2. `ReverseLookup(uint8) uint8` - to get the original value using the reversed s-box.
The input must be an 8-bit unsigned integer (`byte/uint8`). The output is an 8-bit unsigned integer as well.
When looking up, a byte is splitted into two tetrads (4-bit unsigned integers). Then the AES S-box is used - the first tetrad is the row number of the table, and the second tetrad is the column number.
### Example of using an S-box:
```golang
import (
"fmt"
"github.com/danielost/sp-box/src/sbox"
)
func foo() {
var b uint8 = 0x2d
sB := sbox.Lookup(b)
rsB := sbox.ReverseLookup(sB)
fmt.Println(b) // 0x2d = 45
fmt.Println(sB) // 0xd8 = 216
fmt.Println(b == rsB) // 0x2d == 0x2d
}
```
In the above example `0x2d` is divided into two tetrads – `0x2` and `0xd`, where `0x2` is the row of the S-box and `0xd` is the column. `0xd8` is the intersection of these values in the AES S-box, which looks as follows:
| | **0x0** | **0x1** | **0x2** | **0x3** | **0x4** | **0x5** | **0x6** | **0x7** | **0x8** | **0x9** | **0xa** | **0xb** | **0xc** | **0xd** | **0xe** | **0xf** |
|------|------|------|------|------|------|------|------|------|------|------|------|------|------|------|------|------|
| **0x0** | 0x63 | 0x7c | 0x77 | 0x7b | 0xf2 | 0x6b | 0x6f | 0xc5 | 0x30 | 0x01 | 0x67 | 0x2b | 0xfe | 0xd7 | 0xab | 0x76 |
| **0x1** | 0xca | 0x82 | 0xc9 | 0x7d | 0xfa | 0x59 | 0x47 | 0xf0 | 0xad | 0xd4 | 0xa2 | 0xaf | 0x9c | 0xa4 | 0x72 | 0xc0 |
| **0x2** | 0xb7 | 0xfd | 0x93 | 0x26 | 0x36 | 0x3f | 0xf7 | 0xcc | 0x34 | 0xa5 | 0xe5 | 0xf1 | 0x71 | 0xd8 | 0x31 | 0x15 |
| **0x3** | 0x04 | 0xc7 | 0x23 | 0xc3 | 0x18 | 0x96 | 0x05 | 0x9a | 0x07 | 0x12 | 0x80 | 0xe2 | 0xeb | 0x27 | 0xb2 | 0x75 |
| **0x4** | 0x09 | 0x83 | 0x2c | 0x1a | 0x1b | 0x6e | 0x5a | 0xa0 | 0x52 | 0x3b | 0xd6 | 0xb3 | 0x29 | 0xe3 | 0x2f | 0x84 |
| **0x5** | 0x53 | 0xd1 | 0x00 | 0xed | 0x20 | 0xfc | 0xb1 | 0x5b | 0x6a | 0xcb | 0xbe | 0x39 | 0x4a | 0x4c | 0x58 | 0xcf |
| **0x6** | 0xd0 | 0xef | 0xaa | 0xfb | 0x43 | 0x4d | 0x33 | 0x85 | 0x45 | 0xf9 | 0x02 | 0x7f | 0x50 | 0x3c | 0x9f | 0xa8 |
| **0x7** | 0x51 | 0xa3 | 0x40 | 0x8f | 0x92 | 0x9d | 0x38 | 0xf5 | 0xbc | 0xb6 | 0xda | 0x21 | 0x10 | 0xff | 0xf3 | 0xd2 |
| **0x8** | 0xcd | 0x0c | 0x13 | 0xec | 0x5f | 0x97 | 0x44 | 0x17 | 0xc4 | 0xa7 | 0x7e | 0x3d | 0x64 | 0x5d | 0x19 | 0x73 |
| **0x9** | 0x60 | 0x81 | 0x4f | 0xdc | 0x22 | 0x2a | 0x90 | 0x88 | 0x46 | 0xee | 0xb8 | 0x14 | 0xde | 0x5e | 0x0b | 0xdb |
| **0xa** | 0xe0 | 0x32 | 0x3a | 0x0a | 0x49 | 0x06 | 0x24 | 0x5c | 0xc2 | 0xd3 | 0xac | 0x62 | 0x91 | 0x95 | 0xe4 | 0x79 |
| **0xb** | 0xe7 | 0xc8 | 0x37 | 0x6d | 0x8d | 0xd5 | 0x4e | 0xa9 | 0x6c | 0x56 | 0xf4 | 0xea | 0x65 | 0x7a | 0xae | 0x08 |
| **0xc** | 0xba | 0x78 | 0x25 | 0x2e | 0x1c | 0xa6 | 0xb4 | 0xc6 | 0xe8 | 0xdd | 0x74 | 0x1f | 0x4b | 0xbd | 0x8b | 0x8a |
| **0xd** | 0x70 | 0x3e | 0xb5 | 0x66 | 0x48 | 0x03 | 0xf6 | 0x0e | 0x61 | 0x35 | 0x57 | 0xb9 | 0x86 | 0xc1 | 0x1d | 0x9e |
| **0xe** | 0xe1 | 0xf8 | 0x98 | 0x11 | 0x69 | 0xd9 | 0x8e | 0x94 | 0x9b | 0x1e | 0x87 | 0xe9 | 0xce | 0x55 | 0x28 | 0xdf |
| **0xf** | 0x8c | 0xa1 | 0x89 | 0x0d | 0xbf | 0xe6 | 0x42 | 0x68 | 0x41 | 0x99 | 0x2d | 0x0f | 0xb0 | 0x54 | 0xbb | 0x16 |
## Using the P-box
The `src/pbox` package has one public function: `Permute(uint8) (uint8, func(uint8) uint8)`. It takes an 8-bit unsigned integer as an input, converts it to a binary representation, shuffles the bits and returns the decimal representation of the permuted binary value as well as a function that is used to get the original value.
Each call to `Permute` randomly shuffles the bits, even in case of multiple calls for the same input. That is why each call returns a function to restore exactly the returned byte.
To randomly permute the bit sequence, [Fisher–Yates shuffle Algorithm](https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle#:~:text=The%20Fisher%E2%80%93Yates%20shuffle%20is,list%20until%20no%20elements%20remain.) was used.
### Example of using a P-box:
```golang
import (
"fmt"
"github.com/danielost/sp-box/src/pbox"
)
func foo() {
var b uint8 = 0x2d
pB, reverse := pbox.Permute(b)
rpB := reverse(pB)
fmt.Println(b) // 45
fmt.Println(pB) // permuted b - pB
fmt.Println(rpB == b)
}
```
## Running the tests
The tests run the s-box and p-box functions for all the values in range `[0;2^8]`
To run the tests, execute this command:
```bash
go test .\tests\
```
or, for the detailed overview:
```bash
go test -v .\tests\
```