Public Access
twislaandClaude Opus 5.5
305818466f
The MeshCore preset is the default for a new device, in the Settings and in the radio before the Scanner is opened. The setting now accepts it: it only took the 7 Meshtastic presets, so MeshCore picked in the App was not saved. Messages on MeshCore's public channel are decrypted with the channel's published key (AES-128, checked with 2 bytes of HMAC-SHA256): the row shows who says they sent it and the start of the text, the details the sender, the time and the whole text. Other channels and private messages stay encrypted. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_0162FokPdvY2KsS4NBfwyWPk
88 lines
2.9 KiB
C++
88 lines
2.9 KiB
C++
#include "aes128.h"
|
|
|
|
#include <cstring>
|
|
|
|
namespace roro::meshcore {
|
|
|
|
namespace {
|
|
// The S-box and its inverse, worked out once rather than typed in.
|
|
struct Tables {
|
|
uint8_t s[256], inv[256];
|
|
Tables() {
|
|
auto rotl = [](uint8_t x, int n) { return static_cast<uint8_t>(x << n | x >> (8 - n)); };
|
|
uint8_t p = 1, q = 1;
|
|
do {
|
|
p = static_cast<uint8_t>(p ^ (p << 1) ^ (p & 0x80 ? 0x1B : 0)); // p times 3
|
|
q ^= static_cast<uint8_t>(q << 1); // q divided by 3
|
|
q ^= static_cast<uint8_t>(q << 2);
|
|
q ^= static_cast<uint8_t>(q << 4);
|
|
if (q & 0x80) q ^= 0x09;
|
|
uint8_t x = static_cast<uint8_t>(q ^ rotl(q, 1) ^ rotl(q, 2) ^ rotl(q, 3) ^ rotl(q, 4) ^ 0x63);
|
|
s[p] = x;
|
|
inv[x] = p;
|
|
} while (p != 1);
|
|
s[0] = 0x63;
|
|
inv[0x63] = 0;
|
|
}
|
|
};
|
|
const Tables& tables() {
|
|
static const Tables t;
|
|
return t;
|
|
}
|
|
|
|
uint8_t mul(uint8_t a, uint8_t b) { // in GF(2^8)
|
|
uint8_t r = 0;
|
|
for (; b; b >>= 1) {
|
|
if (b & 1) r ^= a;
|
|
a = static_cast<uint8_t>(a << 1 ^ (a & 0x80 ? 0x1B : 0));
|
|
}
|
|
return r;
|
|
}
|
|
} // namespace
|
|
|
|
Aes128::Aes128(const uint8_t key[16]) {
|
|
const Tables& t = tables();
|
|
std::memcpy(roundKeys_, key, 16);
|
|
uint8_t rcon = 1;
|
|
for (int i = 16; i < 176; i += 4) {
|
|
uint8_t w[4];
|
|
std::memcpy(w, roundKeys_ + i - 4, 4);
|
|
if (i % 16 == 0) {
|
|
uint8_t first = w[0];
|
|
w[0] = static_cast<uint8_t>(t.s[w[1]] ^ rcon);
|
|
w[1] = t.s[w[2]];
|
|
w[2] = t.s[w[3]];
|
|
w[3] = t.s[first];
|
|
rcon = static_cast<uint8_t>(rcon << 1 ^ (rcon & 0x80 ? 0x1B : 0));
|
|
}
|
|
for (int j = 0; j < 4; ++j) roundKeys_[i + j] = roundKeys_[i - 16 + j] ^ w[j];
|
|
}
|
|
}
|
|
|
|
void Aes128::decryptBlock(const uint8_t in[16], uint8_t out[16]) const {
|
|
const Tables& t = tables();
|
|
uint8_t s[16];
|
|
for (int i = 0; i < 16; ++i) s[i] = in[i] ^ roundKeys_[160 + i];
|
|
for (int round = 9; round >= 0; --round) {
|
|
// Rows shifted back and bytes substituted back, in one go: column c, row r came from column c - r.
|
|
uint8_t u[16];
|
|
for (int c = 0; c < 4; ++c)
|
|
for (int r = 0; r < 4; ++r) u[4 * c + r] = t.inv[s[4 * ((c - r + 4) % 4) + r]];
|
|
for (int i = 0; i < 16; ++i) u[i] ^= roundKeys_[16 * round + i];
|
|
if (round == 0) {
|
|
std::memcpy(s, u, 16);
|
|
break;
|
|
}
|
|
for (int c = 0; c < 4; ++c) {
|
|
const uint8_t* a = u + 4 * c;
|
|
s[4 * c + 0] = mul(a[0], 14) ^ mul(a[1], 11) ^ mul(a[2], 13) ^ mul(a[3], 9);
|
|
s[4 * c + 1] = mul(a[0], 9) ^ mul(a[1], 14) ^ mul(a[2], 11) ^ mul(a[3], 13);
|
|
s[4 * c + 2] = mul(a[0], 13) ^ mul(a[1], 9) ^ mul(a[2], 14) ^ mul(a[3], 11);
|
|
s[4 * c + 3] = mul(a[0], 11) ^ mul(a[1], 13) ^ mul(a[2], 9) ^ mul(a[3], 14);
|
|
}
|
|
}
|
|
std::memcpy(out, s, 16);
|
|
}
|
|
|
|
} // namespace roro::meshcore
|