CI fix

32-bit stuff
Rohde-Schwarz · Mar 8, 2024 · f21cb0c · f21cb0c
1 parent 9e6afc7
commit f21cb0c
Showing 1 changed file with 25 additions and 14 deletions.
diff --git a/src/lib/pubkey/curve448/curve448_utils/curve448_scalar.cpp b/src/lib/pubkey/curve448/curve448_utils/curve448_scalar.cpp
@@ -35,18 +35,35 @@ std::pair<std::array<word, S - WORDS_446 + 1>, std::array<word, WORDS_446>> div_
    return {q, r};
 }
 
+template <size_t S>
+consteval std::array<word, S / sizeof(word)> load_words(const std::array<uint8_t, S>& bytes)
+   requires(S % sizeof(word) == 0)
+{
+   // Currently load_le does not work with constexpr. Therefore, we have to use this workaround.
+   std::array<word, S / sizeof(word)> res = {0};
+   for(size_t i = 0; i < bytes.size(); ++i) {
+      res[i / sizeof(word)] |= word(bytes[i]) << ((i % sizeof(word)) * 8);
+   }
+
+   return res;
+}
+
 /// @return a word array for c = 0x8335dc163bb124b65129c96fde933d8d723a70aadc873d6d54a7bb0d
 consteval std::array<word, WORDS_C> c_words() {
    // Currently load_le does not work with constexpr. Therefore, we have to use this workaround.
    const std::array<uint8_t, WORDS_C * sizeof(word)> c_bytes{0x0d, 0xbb, 0xa7, 0x54, 0x6d, 0x3d, 0x87, 0xdc, 0xaa, 0x70,
                                                              0x3a, 0x72, 0x8d, 0x3d, 0x93, 0xde, 0x6f, 0xc9, 0x29, 0x51,
                                                              0xb6, 0x24, 0xb1, 0x3b, 0x16, 0xdc, 0x35, 0x83};
-   std::array<word, WORDS_C> res = {0};
-   for(size_t i = 0; i < c_bytes.size(); ++i) {
-      res[i / sizeof(word)] |= word(c_bytes[i]) << ((i % sizeof(word)) * 8);
-   }
+   return load_words(c_bytes);
+}
 
-   return res;
+/// @return a word array for L = 2^446 - 0x8335dc163bb124b65129c96fde933d8d723a70aadc873d6d54a7bb0d
+consteval std::array<word, WORDS_446> big_l_words() {
+   const std::array<uint8_t, WORDS_446 * sizeof(word)> big_l_bytes{
+      0xf3, 0x44, 0x58, 0xab, 0x92, 0xc2, 0x78, 0x23, 0x55, 0x8f, 0xc5, 0x8d, 0x72, 0xc2, 0x6c, 0x21, 0x90, 0x36, 0xd6,
+      0xae, 0x49, 0xdb, 0x4e, 0xc4, 0xe9, 0x23, 0xca, 0x7c, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x3f};
+   return load_words(big_l_bytes);
 }
 
 /// @return c*x, with c = 0x8335dc163bb124b65129c96fde933d8d723a70aadc873d6d54a7bb0d
@@ -79,15 +96,9 @@ std::array<word, WORDS_446> add(std::span<const word, WORDS_446> x, std::span<co
 bool ct_subtract_L_if_bigger(std::span<word, WORDS_446> x) {
    std::array<word, WORDS_446> tmp;
    copy_mem(tmp, x);
-   constexpr std::array<word, WORDS_446> L = {0x2378c292ab5844f3,
-                                              0x216cc2728dc58f55,
-                                              0xc44edb49aed63690,
-                                              0xffffffff7cca23e9,
-                                              0xffffffffffffffff,
-                                              0xffffffffffffffff,
-                                              0x3fffffffffffffff};
-
-   const word borrow = bigint_sub2(tmp.data(), tmp.size(), L.data(), L.size());
+   constexpr auto big_l = big_l_words();
+
+   const word borrow = bigint_sub2(tmp.data(), tmp.size(), big_l.data(), big_l.size());
    const auto smaller_than_L = CT::Mask<word>::expand(borrow);
    smaller_than_L.select_n(x.data(), x.data(), tmp.data(), WORDS_446);