1 files changed, 116 insertions, 0 deletions
diff --git a/third_party/heimdal/lib/hcrypto/x25519/fe_51/fe.h b/third_party/heimdal/lib/hcrypto/x25519/fe_51/fe.h
new file mode 100644
index 0000000..de87626
--- /dev/null
+++ b/third_party/heimdal/lib/hcrypto/x25519/fe_51/fe.h
@@ -0,0 +1,116 @@
+/*
+ Ignores top bit of h.
+ */
+
+void
+fe25519_frombytes(fe25519 h, const unsigned char *s)
+{
+    const uint64_t mask = 0x7ffffffffffffULL;
+    uint64_t h0, h1, h2, h3, h4;
+
+    h0 = (LOAD64_LE(s     )      ) & mask;
+    h1 = (LOAD64_LE(s +  6) >>  3) & mask;
+    h2 = (LOAD64_LE(s + 12) >>  6) & mask;
+    h3 = (LOAD64_LE(s + 19) >>  1) & mask;
+    h4 = (LOAD64_LE(s + 24) >> 12) & mask;
+
+    h[0] = h0;
+    h[1] = h1;
+    h[2] = h2;
+    h[3] = h3;
+    h[4] = h4;
+}
+
+static void
+fe25519_reduce(fe25519 h, const fe25519 f)
+{
+    const uint64_t mask = 0x7ffffffffffffULL;
+    uint128_t t[5];
+
+    t[0] = f[0];
+    t[1] = f[1];
+    t[2] = f[2];
+    t[3] = f[3];
+    t[4] = f[4];
+
+    t[1] += t[0] >> 51;
+    t[0] &= mask;
+    t[2] += t[1] >> 51;
+    t[1] &= mask;
+    t[3] += t[2] >> 51;
+    t[2] &= mask;
+    t[4] += t[3] >> 51;
+    t[3] &= mask;
+    t[0] += 19 * (t[4] >> 51);
+    t[4] &= mask;
+
+    t[1] += t[0] >> 51;
+    t[0] &= mask;
+    t[2] += t[1] >> 51;
+    t[1] &= mask;
+    t[3] += t[2] >> 51;
+    t[2] &= mask;
+    t[4] += t[3] >> 51;
+    t[3] &= mask;
+    t[0] += 19 * (t[4] >> 51);
+    t[4] &= mask;
+
+    /* now t is between 0 and 2^255-1, properly carried. */
+    /* case 1: between 0 and 2^255-20. case 2: between 2^255-19 and 2^255-1. */
+
+    t[0] += 19ULL;
+
+    t[1] += t[0] >> 51;
+    t[0] &= mask;
+    t[2] += t[1] >> 51;
+    t[1] &= mask;
+    t[3] += t[2] >> 51;
+    t[2] &= mask;
+    t[4] += t[3] >> 51;
+    t[3] &= mask;
+    t[0] += 19ULL * (t[4] >> 51);
+    t[4] &= mask;
+
+    /* now between 19 and 2^255-1 in both cases, and offset by 19. */
+
+    t[0] += 0x8000000000000 - 19ULL;
+    t[1] += 0x8000000000000 - 1ULL;
+    t[2] += 0x8000000000000 - 1ULL;
+    t[3] += 0x8000000000000 - 1ULL;
+    t[4] += 0x8000000000000 - 1ULL;
+
+    /* now between 2^255 and 2^256-20, and offset by 2^255. */
+
+    t[1] += t[0] >> 51;
+    t[0] &= mask;
+    t[2] += t[1] >> 51;
+    t[1] &= mask;
+    t[3] += t[2] >> 51;
+    t[2] &= mask;
+    t[4] += t[3] >> 51;
+    t[3] &= mask;
+    t[4] &= mask;
+
+    h[0] = t[0];
+    h[1] = t[1];
+    h[2] = t[2];
+    h[3] = t[3];
+    h[4] = t[4];
+}
+
+void
+fe25519_tobytes(unsigned char *s, const fe25519 h)
+{
+    fe25519  t;
+    uint64_t t0, t1, t2, t3;
+
+    fe25519_reduce(t, h);
+    t0 = t[0] | (t[1] << 51);
+    t1 = (t[1] >> 13) | (t[2] << 38);
+    t2 = (t[2] >> 26) | (t[3] << 25);
+    t3 = (t[3] >> 39) | (t[4] << 12);
+    STORE64_LE(s +  0, t0);
+    STORE64_LE(s +  8, t1);
+    STORE64_LE(s + 16, t2);
+    STORE64_LE(s + 24, t3);
+}