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I never realized how much I hate DES

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This commit is contained in:
Milan Špinka
2025-02-02 01:11:25 +01:00
parent 3afe9895c5
commit ba3802ebcc
1 changed files with 53 additions and 14 deletions
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67
src/primitive/blockcipher/des.zig
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@ -42,6 +42,17 @@ const DES_BIT_SELECTION_TABLE_E = [_]u5{
28, 29, 30, 31, 32, 1,
};
const DES_S_BOXES = [8][64]u4{
.{ 14, 0, 4, 15, 13, 7, 1, 4, 2, 14, 15, 2, 11, 13, 8, 1, 3, 10, 10, 6, 6, 12, 12, 11, 5, 9, 9, 5, 0, 3, 7, 8, 4, 15, 1, 12, 14, 8, 8, 2, 13, 4, 6, 9, 2, 1, 11, 7, 15, 5, 12, 11, 9, 3, 7, 14, 3, 10, 10, 0, 5, 6, 0, 13 },
.{ 15, 3, 1, 13, 8, 4, 14, 7, 6, 15, 11, 2, 3, 8, 4, 14, 9, 12, 7, 0, 2, 1, 13, 10, 12, 6, 0, 9, 5, 11, 10, 5, 0, 13, 14, 8, 7, 10, 11, 1, 10, 3, 4, 15, 13, 4, 1, 2, 5, 11, 8, 6, 12, 7, 6, 12, 9, 0, 3, 5, 2, 14, 15, 9 },
.{ 10, 13, 0, 7, 9, 0, 14, 9, 6, 3, 3, 4, 15, 6, 5, 10, 1, 2, 13, 8, 12, 5, 7, 14, 11, 12, 4, 11, 2, 15, 8, 1, 13, 1, 6, 10, 4, 13, 9, 0, 8, 6, 15, 9, 3, 8, 0, 7, 11, 4, 1, 15, 2, 14, 12, 3, 5, 11, 10, 5, 14, 2, 7, 12 },
.{ 7, 13, 13, 8, 14, 11, 3, 5, 0, 6, 6, 15, 9, 0, 10, 3, 1, 4, 2, 7, 8, 2, 5, 12, 11, 1, 12, 10, 4, 14, 15, 9, 10, 3, 6, 15, 9, 0, 0, 6, 12, 10, 11, 1, 7, 13, 13, 8, 15, 9, 1, 4, 3, 5, 14, 11, 5, 12, 2, 7, 8, 2, 4, 14 },
.{ 2, 14, 12, 11, 4, 2, 1, 12, 7, 4, 10, 7, 11, 13, 6, 1, 8, 5, 5, 0, 3, 15, 15, 10, 13, 3, 0, 9, 14, 8, 9, 6, 4, 11, 2, 8, 1, 12, 11, 7, 10, 1, 13, 14, 7, 2, 8, 13, 15, 6, 9, 15, 12, 0, 5, 9, 6, 10, 3, 4, 0, 5, 14, 3 },
.{ 12, 10, 1, 15, 10, 4, 15, 2, 9, 7, 2, 12, 6, 9, 8, 5, 0, 6, 13, 1, 3, 13, 4, 14, 14, 0, 7, 11, 5, 3, 11, 8, 9, 4, 14, 3, 15, 2, 5, 12, 2, 9, 8, 5, 12, 15, 3, 10, 7, 11, 0, 14, 4, 1, 10, 7, 1, 6, 13, 0, 11, 8, 6, 13 },
.{ 4, 13, 11, 0, 2, 11, 14, 7, 15, 4, 0, 9, 8, 1, 13, 10, 3, 14, 12, 3, 9, 5, 7, 12, 5, 2, 10, 15, 6, 8, 1, 6, 1, 6, 4, 11, 11, 13, 13, 8, 12, 1, 3, 4, 7, 10, 14, 7, 10, 9, 15, 5, 6, 0, 8, 15, 0, 14, 5, 2, 9, 3, 2, 12 },
.{ 13, 1, 2, 15, 8, 13, 4, 8, 6, 10, 15, 3, 11, 7, 1, 4, 10, 12, 9, 5, 3, 6, 14, 11, 5, 0, 0, 14, 12, 9, 7, 2, 7, 2, 11, 1, 4, 14, 1, 7, 9, 4, 12, 10, 14, 8, 2, 13, 0, 15, 6, 12, 10, 9, 13, 0, 15, 3, 3, 5, 5, 6, 8, 11 },
};
const DES_PERMUTATION_FUNCTION_P = [_]u5{
16, 7, 20, 21, 29, 12, 28, 17,
1, 15, 23, 26, 5, 18, 31, 10,
@ -88,12 +99,18 @@ pub fn des_decrypt_block(
}
pub fn des_expand_key(key: *const [DES_ENCODED_KEY_SIZE]u8) [DES_N_ROUNDS][DES_SUBKEY_SIZE]u8 {
var cd = des_permuted_choice_1(key);
const cd = des_permuted_choice_1(key);
// Probably the least stupid software implementation that I could think of.
var c_i = @as(u28, std.mem.readInt(u56, &cd, .big) >> 28);
var d_i = @as(u28, std.mem.readInt(u56, &cd, .big) & 0xfffffff);
var subkeys: [DES_N_ROUNDS][DES_SUBKEY_SIZE]u8 = undefined;
for (0..DES_N_ROUNDS) |i| {
rotate_halves_left(cd[0..], DES_KS_SHIFT_SCHEDULE[i]);
des_permuted_choice_2(cd, &subkeys[i]);
c_i = rotate_left(c_i, DES_KS_SHIFT_SCHEDULE[i]);
d_i = rotate_left(d_i, DES_KS_SHIFT_SCHEDULE[i]);
des_permuted_choice_2(c_i, d_i, &subkeys[i]);
}
}
@ -109,13 +126,17 @@ pub fn des_permuted_choice_1(key: *const [DES_ENCODED_KEY_SIZE]u8) [DES_TRUE_KEY
return result;
}
pub fn des_permuted_choice_2(cd: *const [DES_TRUE_KEY_SIZE]u8, out: *[DES_SUBKEY_SIZE]u8) void {
pub fn des_permuted_choice_2(c: u28, d: u28, out: *[DES_SUBKEY_SIZE]u8) void {
const PC2 = .{
14, 17, 11, 24, 1, 5, 3, 28, 15, 6, 21, 10, 23, 19, 12, 4, 26, 8, 16, 7, 27, 20, 13, 2,
41, 52, 31, 37, 47, 55, 30, 40, 51, 45, 33, 48, 44, 49, 39, 56, 34, 53, 46, 42, 50, 36, 29, 32,
};
permute_bits(DES_SUBKEY_SIZE, cd, out, PC2);
const cd = @as(u56, c) << 28 | @as(u56, d);
const cd_bytes: [DES_TRUE_KEY_SIZE]u8 = undefined;
std.mem.writeInt(u56, &cd_bytes, cd, .big);
permute_bits(DES_SUBKEY_SIZE, &cd_bytes, out, PC2);
}
pub fn des_perform_round(state: *[DES_BLOCK_SIZE]u8, subkey: *[DES_SUBKEY_SIZE]u8) void {
@ -134,8 +155,21 @@ pub fn des_cipher_function_f(word: [DES_BLOCK_SIZE / 2]u8, subkey: *const [DES_S
for (0..DES_SUBKEY_SIZE) |i|
expanded_word[i] ^= subkey[i];
// todo
_ = .{ word, subkey };
var sbox_output = std.mem.zeroes([DES_BLOCK_SIZE / 2]u8);
inline for (0..8) |i| {
var sbox_input: u6 = @as(u6, get_nth_bit(DES_SUBKEY_SIZE, &expanded_word, i * 6));
for (1..6) |j| {
sbox_input <<= 1;
sbox_input |= @as(u6, get_nth_bit(DES_SUBKEY_SIZE, &expanded_word, i * 6 + j));
}
sbox_output[i / 2] |= DES_S_BOXES[i][sbox_input] << if (i % 2 == 0) 4 else 0;
}
var expansion_output: [DES_BLOCK_SIZE / 2]u8 = undefined;
permute_bits(DES_BLOCK_SIZE / 2, &sbox_output, &expansion_output, &DES_PERMUTATION_FUNCTION_P);
return expansion_output;
}
pub fn des_initial_permutation(in: *const [DES_BLOCK_SIZE]u8, out: *[DES_BLOCK_SIZE]u8) void {
@ -153,19 +187,25 @@ fn permute_bits(L: comptime_int, in: []u8, out: *[L]u8, key: [8 * L]u6) void {
const pi = key[i];
if (pi >= in.len * 8)
@panic("Bit index out of range!");
const bit = get_nth_bit(in, pi);
set_nth_bit(out, pi, bit);
const bit = get_nth_bit(8, in, pi);
set_nth_bit(8, out, pi, bit);
}
}
fn get_nth_bit(bytes: *const [8]u8, n: u6) u1 {
fn get_nth_bit(comptime L: u3, bytes: *const [L]u8, n: u6) u1 {
if (L > 8 or n >= L * 8)
@panic("Bit index out of range!");
const byte_idx = n / 8;
const bit_idx = n % 8;
return @truncate(bytes[byte_idx] >> (7 - bit_idx));
}
fn set_nth_bit(bytes: *const [8]u8, n: u6, bit: u1) void {
fn set_nth_bit(comptime L: u3, bytes: *const [8]u8, n: u6, bit: u1) void {
if (n >= L * 8)
@panic("Bit index out of range!");
const byte_idx = n / 8;
const bit_idx = n % 8;
@ -182,7 +222,6 @@ fn xor(L: comptime_int, a: [L]u8, b: [L]u8) [L]u8 {
return result;
}
fn rotate_halves_left(cd: *[DES_TRUE_KEY_SIZE]u8, positions: comptime_int) void {
// TODO
_ = .{ cd, positions };
fn rotate_left(x: u28, positions: comptime_int) u28 {
return x << positions | x >> (28 - positions);
}