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better implementation of x25519

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orignal 2018-06-19 11:14:22 -04:00
parent 58c92b8405
commit 9c7cadb191
1 changed files with 22 additions and 43 deletions
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65
libi2pd/Ed25519.cpp
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@ -419,13 +419,8 @@ namespace crypto
auto z2 = BN_CTX_get (ctx); BN_zero (z2);
auto x3 = BN_CTX_get (ctx); BN_copy (x3, u);
auto z3 = BN_CTX_get (ctx); BN_one (z3);
auto a24 = BN_CTX_get (ctx); BN_set_word (a24, 121665);
auto a = BN_CTX_get (ctx); auto aa = BN_CTX_get (ctx);
auto b = BN_CTX_get (ctx); auto bb = BN_CTX_get (ctx);
auto e = BN_CTX_get (ctx); auto c = BN_CTX_get (ctx);
auto d = BN_CTX_get (ctx);
auto da = BN_CTX_get (ctx); auto cb = BN_CTX_get (ctx);
auto tmp1 = BN_CTX_get (ctx); auto tmp2 = BN_CTX_get (ctx);
auto c121666 = BN_CTX_get (ctx); BN_set_word (c121666, 121666);
auto tmp0 = BN_CTX_get (ctx); auto tmp1 = BN_CTX_get (ctx);
unsigned int swap = 0;
auto bits = BN_num_bits (k);
while(bits)
@ -439,49 +434,33 @@ namespace crypto
std::swap (z2, z3);
}
swap = k_t;
// a = x2 + z2
BN_mod_add(a, x2, z2, q, ctx);
// aa = a^2
BN_mod_sqr(aa, a, q, ctx);
// b = x2 - z2
BN_mod_sub(b, x2, z2, q, ctx);
// bb = b^2
BN_mod_sqr(bb, b, q, ctx);
// e = aa - bb
BN_mod_sub(e, aa, bb, q, ctx);
// c = x3 + z3
BN_mod_add(c, x3, z3, q, ctx);
// d = x3 - z3
BN_mod_sub(d, x3, z3, q, ctx);
// da = d * a
BN_mod_mul(da, d, a, q, ctx);
// cb = c * b
BN_mod_mul(cb, c, b, q, ctx);
// x3 = ( da + cb )^2
BN_mod_add(tmp1, da, cb, q, ctx);
BN_mod_sqr(x3, tmp1, q, ctx);
// z3 == x1 * (da - cb)^2
BN_mod_sub(tmp1, da, cb, q, ctx);
BN_mod_sqr(tmp2, tmp1, q, ctx);
BN_mod_mul(z3, x1, tmp2, q, ctx);
// x2 = aa * bb
BN_mod_mul(x2, aa, bb, q, ctx);
// z2 = e * (aa + a24 * e)
BN_mod_mul(tmp1, a24, e, q, ctx);
BN_mod_add(tmp2, aa, tmp1, q, ctx);
BN_mod_mul(z2, e, tmp2, q, ctx);
BN_mod_sub(tmp0, x3, z3, q, ctx);
BN_mod_sub(tmp1, x2, z2, q, ctx);
BN_mod_add(x2, x2, z2, q, ctx);
BN_mod_add(z2, x3, z3, q, ctx);
BN_mod_mul(z3, tmp0, x2, q, ctx);
BN_mod_mul(z2, z2, tmp1, q, ctx);
BN_mod_sqr(tmp0, tmp1, q, ctx);
BN_mod_sqr(tmp1, x2, q, ctx);
BN_mod_add(x3, z3, z2, q, ctx);
BN_mod_sub(z2, z3, z2, q, ctx);
BN_mod_mul(x2, tmp1, tmp0, q, ctx);
BN_mod_sub(tmp1, tmp1, tmp0, q, ctx);
BN_mod_sqr(z2, z2, q, ctx);
BN_mod_mul(z3, tmp1, c121666, q, ctx);
BN_mod_sqr(x3, x3, q, ctx);
BN_mod_add(tmp0, tmp0, z3, q, ctx);
BN_mod_mul(z3, x1, z2, q, ctx);
BN_mod_mul(z2, tmp1, tmp0, q, ctx);
}
if (swap)
{
std::swap (x2, x3);
std::swap (z2, z3);
}
// x2 * (z2 ^ (q - 2))
BN_set_word(tmp1, 2);
BN_sub(tmp2, q, tmp1);
BN_mod_exp(tmp1, z2, tmp2, q, ctx);
BN_mod_inverse (z2, z2, q, ctx);
BIGNUM * res = BN_new (); // not from ctx
BN_mod_mul(res, x2, tmp1, q, ctx);
BN_mod_mul(res, x2, z2, q, ctx);
BN_CTX_end (ctx);
return res;
}