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Just randomize the data, not the address 

Signed-off-by: Joachim Strömbergson <joachim@assured.se>
This commit is contained in:
Joachim Strömbergson 2024-04-05 08:00:17 +02:00 committed by Michael Cardell Widerkrantz
parent 3dff3e6b4e
commit 3ddd047994
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GPG Key ID: D3DB3DDF57E704E5
1 changed files with 4 additions and 9 deletions
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13
hw/application_fpga/fw/tk1/main.c
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@ -380,22 +380,17 @@ static void scramble_ram(void)
*ram_rand = rnd_word();
*ram_scramble = rnd_word();
// Use Marsaglia xorshift PRNG variant xorwow for address and
// data to fill the RAM random data (FW does not use RAM, has
// its stack in FW_RAM)
uint32_t addr_state = rnd_word();
uint32_t addr_acc = rnd_word();
// Get random state and accumulator seeds.
uint32_t data_state = rnd_word();
uint32_t data_acc = rnd_word();
for (uint32_t w = 0; w < TK1_RAM_SIZE / 4; w++) {
addr_state = xorwow(addr_state, addr_acc);
data_state = xorwow(data_state, data_acc);
ram[(addr_state & TK1_RAM_SIZE)] = data_state;
ram[w] = data_state;
}
// Set new scrambling values, for all use of RAM by app
// Set new address and RAM scrambling values,
// for all use of RAM by app.
*ram_rand = rnd_word();
*ram_scramble = rnd_word();
}