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Simple script to determine if an S-Box is linear
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| from sage.crypto.boolean_function import BooleanFunction | |
| def is_linear_sbox(sbox: list[int]) -> bool: | |
| input_size = (len(sbox) - 1).bit_length() | |
| output_size = max(sbox).bit_length() | |
| print(f"[*] Input bits: {input_size}, Output bits: {output_size}") | |
| is_linear = True | |
| for bit_index in range(output_size): | |
| truth_table = [(sbox[i] >> bit_index) & 1 for i in range(2**input_size)] | |
| f = BooleanFunction(truth_table) | |
| deg = f.algebraic_degree() | |
| print(f"[+] The {bit_index} bit output function's algebra degree: {deg}") | |
| if deg > 1: | |
| is_linear = False | |
| break | |
| return is_linear |
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