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-rw-r--r--jni/ed25519/fe_cmov.c63
1 files changed, 63 insertions, 0 deletions
diff --git a/jni/ed25519/fe_cmov.c b/jni/ed25519/fe_cmov.c
new file mode 100644
index 00000000..8ca584fb
--- /dev/null
+++ b/jni/ed25519/fe_cmov.c
@@ -0,0 +1,63 @@
+#include "fe.h"
+
+/*
+Replace (f,g) with (g,g) if b == 1;
+replace (f,g) with (f,g) if b == 0.
+
+Preconditions: b in {0,1}.
+*/
+
+void fe_cmov(fe f,const fe g,unsigned int b)
+{
+ crypto_int32 f0 = f[0];
+ crypto_int32 f1 = f[1];
+ crypto_int32 f2 = f[2];
+ crypto_int32 f3 = f[3];
+ crypto_int32 f4 = f[4];
+ crypto_int32 f5 = f[5];
+ crypto_int32 f6 = f[6];
+ crypto_int32 f7 = f[7];
+ crypto_int32 f8 = f[8];
+ crypto_int32 f9 = f[9];
+ crypto_int32 g0 = g[0];
+ crypto_int32 g1 = g[1];
+ crypto_int32 g2 = g[2];
+ crypto_int32 g3 = g[3];
+ crypto_int32 g4 = g[4];
+ crypto_int32 g5 = g[5];
+ crypto_int32 g6 = g[6];
+ crypto_int32 g7 = g[7];
+ crypto_int32 g8 = g[8];
+ crypto_int32 g9 = g[9];
+ crypto_int32 x0 = f0 ^ g0;
+ crypto_int32 x1 = f1 ^ g1;
+ crypto_int32 x2 = f2 ^ g2;
+ crypto_int32 x3 = f3 ^ g3;
+ crypto_int32 x4 = f4 ^ g4;
+ crypto_int32 x5 = f5 ^ g5;
+ crypto_int32 x6 = f6 ^ g6;
+ crypto_int32 x7 = f7 ^ g7;
+ crypto_int32 x8 = f8 ^ g8;
+ crypto_int32 x9 = f9 ^ g9;
+ b = -b;
+ x0 &= b;
+ x1 &= b;
+ x2 &= b;
+ x3 &= b;
+ x4 &= b;
+ x5 &= b;
+ x6 &= b;
+ x7 &= b;
+ x8 &= b;
+ x9 &= b;
+ f[0] = f0 ^ x0;
+ f[1] = f1 ^ x1;
+ f[2] = f2 ^ x2;
+ f[3] = f3 ^ x3;
+ f[4] = f4 ^ x4;
+ f[5] = f5 ^ x5;
+ f[6] = f6 ^ x6;
+ f[7] = f7 ^ x7;
+ f[8] = f8 ^ x8;
+ f[9] = f9 ^ x9;
+}