1 files changed, 105 insertions, 0 deletions
diff --git a/jni/ed25519/ge_scalarmult_base.c b/jni/ed25519/ge_scalarmult_base.c
new file mode 100644
index 00000000..421e4fa0
--- /dev/null
+++ b/jni/ed25519/ge_scalarmult_base.c
@@ -0,0 +1,105 @@
+#include "ge.h"
+#include "crypto_uint32.h"
+
+static unsigned char equal(signed char b,signed char c)
+{
+  unsigned char ub = b;
+  unsigned char uc = c;
+  unsigned char x = ub ^ uc; /* 0: yes; 1..255: no */
+  crypto_uint32 y = x; /* 0: yes; 1..255: no */
+  y -= 1; /* 4294967295: yes; 0..254: no */
+  y >>= 31; /* 1: yes; 0: no */
+  return y;
+}
+
+static unsigned char negative(signed char b)
+{
+  unsigned long long x = b; /* 18446744073709551361..18446744073709551615: yes; 0..255: no */
+  x >>= 63; /* 1: yes; 0: no */
+  return x;
+}
+
+static void cmov(ge_precomp *t,ge_precomp *u,unsigned char b)
+{
+  fe_cmov(t->yplusx,u->yplusx,b);
+  fe_cmov(t->yminusx,u->yminusx,b);
+  fe_cmov(t->xy2d,u->xy2d,b);
+}
+
+/* base[i][j] = (j+1)*256^i*B */
+static ge_precomp base[32][8] = {
+#include "base.h"
+} ;
+
+static void select(ge_precomp *t,int pos,signed char b)
+{
+  ge_precomp minust;
+  unsigned char bnegative = negative(b);
+  unsigned char babs = b - (((-bnegative) & b) << 1);
+
+  ge_precomp_0(t);
+  cmov(t,&base[pos][0],equal(babs,1));
+  cmov(t,&base[pos][1],equal(babs,2));
+  cmov(t,&base[pos][2],equal(babs,3));
+  cmov(t,&base[pos][3],equal(babs,4));
+  cmov(t,&base[pos][4],equal(babs,5));
+  cmov(t,&base[pos][5],equal(babs,6));
+  cmov(t,&base[pos][6],equal(babs,7));
+  cmov(t,&base[pos][7],equal(babs,8));
+  fe_copy(minust.yplusx,t->yminusx);
+  fe_copy(minust.yminusx,t->yplusx);
+  fe_neg(minust.xy2d,t->xy2d);
+  cmov(t,&minust,bnegative);
+}
+
+/*
+h = a * B
+where a = a[0]+256*a[1]+...+256^31 a[31]
+B is the Ed25519 base point (x,4/5) with x positive.
+
+Preconditions:
+  a[31] <= 127
+*/
+
+void ge_scalarmult_base(ge_p3 *h,const unsigned char *a)
+{
+  signed char e[64];
+  signed char carry;
+  ge_p1p1 r;
+  ge_p2 s;
+  ge_precomp t;
+  int i;
+
+  for (i = 0;i < 32;++i) {
+    e[2 * i + 0] = (a[i] >> 0) & 15;
+    e[2 * i + 1] = (a[i] >> 4) & 15;
+  }
+  /* each e[i] is between 0 and 15 */
+  /* e[63] is between 0 and 7 */
+
+  carry = 0;
+  for (i = 0;i < 63;++i) {
+    e[i] += carry;
+    carry = e[i] + 8;
+    carry >>= 4;
+    e[i] -= carry << 4;
+  }
+  e[63] += carry;
+  /* each e[i] is between -8 and 8 */
+
+  ge_p3_0(h);
+  for (i = 1;i < 64;i += 2) {
+    select(&t,i / 2,e[i]);
+    ge_madd(&r,h,&t); ge_p1p1_to_p3(h,&r);
+  }
+
+  ge_p3_dbl(&r,h);  ge_p1p1_to_p2(&s,&r);
+  ge_p2_dbl(&r,&s); ge_p1p1_to_p2(&s,&r);
+  ge_p2_dbl(&r,&s); ge_p1p1_to_p2(&s,&r);
+  ge_p2_dbl(&r,&s); ge_p1p1_to_p3(h,&r);
+
+  for (i = 0;i < 64;i += 2) {
+    select(&t,i / 2,e[i]);
+    ge_madd(&r,h,&t); ge_p1p1_to_p3(h,&r);
+  }
+}