feat: AES decryption #124
feat: AES decryption #124
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src/encryption/symmetric/aes/mod.rs
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| /// element is treated as a polynomial. | ||
| /// | ||
| /// NOTE: this multiplication is not commutative - ie. A * B may not equal B * A. | ||
| fn galois_multiplication(mut col: u8, mut multiplicant: usize) -> u8 { |
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just want to get others' opinions, is it possible to use
I think this will make traversing the code a bit simpler, but might make other operations like SubBytes/AddRoundKeys more difficult.
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Yeah that's a good point, in some parts of the code (such as this) we are indeed operating in GaloisField implemented), and that should really be the main goal.
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I think this would be a good idea. It would be nice to stand on the other primitives we have so we don't have to reinvent them every time
This commit contains 2 main changes: Updates to documentation, Using 7-degree polynomials of `BinaryField`s to represent bytes to do a multiplication instead of doing carry-less multiplication.
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src/field/binary_towers/tests.rs
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This big diff is just me moving the impls into a generalized GaloisField<8, 2>, now found in gf_2_8.rs
Closes #119
Some key notes/changes:
galois_multiplicationto be used formix_columns: for encryption, we only needed to multiply column values once at worst to do a matrix multiplication for the polynomial a(x) = 3x^3 + x^2 + x + 2, so we could do it withinmix_columns(), but since the inverseinv_mix_columnsuses a more complex polynomial (the inverse of a, a^-1(x) = 11x^3 + 13x^2 + 9x + 14), it would be cleaner to properly implement this fn.shift_rowsimpl since I realized we could simply just userotate_leftandrotate_rightfound in Rust stdlib.