diff options
| -rw-r--r-- | src/ec25519.c | 29 |
1 files changed, 16 insertions, 13 deletions
diff --git a/src/ec25519.c b/src/ec25519.c index 6458d2d..d35e368 100644 --- a/src/ec25519.c +++ b/src/ec25519.c @@ -194,15 +194,16 @@ static const unsigned int rho_s[32] = { }; static const unsigned int zero[32] = {0}; -static const unsigned int minus1[32] = { - 0xec, 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, 0xff, 0xff, 0xff, 0x7f -}; static void square_root(unsigned int out[32], const unsigned int z[32]) { - /* raise z to the (2^252-2)th power */ + static const unsigned int minus1[32] = { + 0xec, 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, 0xff, 0xff, 0xff, 0x7f + }; + + /* raise z to power (2^252-2), check if power (2^253-5) equals -1 */ unsigned int z2[32]; unsigned int z9[32]; @@ -214,7 +215,8 @@ static void square_root(unsigned int out[32], const unsigned int z[32]) { unsigned int z2_100_0[32]; unsigned int t0[32]; unsigned int t1[32]; - unsigned int rt_sq[32]; + unsigned int z2_252_1[32]; + unsigned int z2_252_1_rho_s[32]; int i; /* 2 */ square(z2, z); @@ -264,14 +266,15 @@ static void square_root(unsigned int out[32], const unsigned int z[32]) { /* 2^251 - 2^1 */ square(t1, t0); /* 2^252 - 2^2 */ square(t0, t1); + /* 2^252 - 2^1 */ mult(z2_252_1, t0, z2); - /* 2^252 - 2 */ mult(t1, t0, z2); - - mult(t0, t1, rho_s); + /* 2^253 - 2^3 */ square(t1, t0); + /* 2^253 - 6 */ mult(t0, t1, z2); + /* 2^253 - 5 */ mult(t1, t0, z); - square(rt_sq, t1); + mult(z2_252_1_rho_s, z2_252_1, rho_s); - select(out, t0, t1, check_equal(rt_sq, minus1)); + select(out, z2_252_1_rho_s, z2_252_1, check_equal(t1, minus1)); } static void recip(unsigned int out[32], const unsigned int z[32]) { |