module X25519::Provider::Precomputed

Public Class Methods

available?() click to toggle source

Is the x25519_precomputed backend supported on this CPU?

static VALUE mX25519_is_available(VALUE self)
{
    return check_4th_gen_intel_core_features() ? Qtrue : Qfalse;
}
scalarmult(p1, p2) click to toggle source

Variable-base scalar multiplication

static VALUE mX25519_Provider_Precomputed_scalarmult(VALUE self, VALUE scalar, VALUE montgomery_u)
{
    /* X25519_KEY ensures inputs are aligned at 32-bytes */
    X25519_KEY raw_scalar, raw_montgomery_u, product;

    StringValue(scalar);
    if(RSTRING_LEN(scalar) != X25519_KEYSIZE_BYTES) {
        rb_raise(
            rb_eArgError,
            "expected %d-byte scalar, got %ld",
            X25519_KEYSIZE_BYTES,
            RSTRING_LEN(scalar)
        );
    }

    StringValue(montgomery_u);
    if(RSTRING_LEN(montgomery_u) != X25519_KEYSIZE_BYTES) {
        rb_raise(
            rb_eArgError,
            "expected %d-byte Montgomery-u coordinate, got %ld",
            X25519_KEYSIZE_BYTES,
            RSTRING_LEN(montgomery_u)
        );
    }

    memcpy(raw_scalar, RSTRING_PTR(scalar), X25519_KEYSIZE_BYTES);
    memcpy(raw_montgomery_u, RSTRING_PTR(montgomery_u), X25519_KEYSIZE_BYTES);
    x25519_precomputed_scalarmult(product, raw_scalar, raw_montgomery_u);

    return rb_str_new((const char *)product, X25519_KEYSIZE_BYTES);
}
scalarmult_base(p1) click to toggle source

Fixed-base scalar multiplication

static VALUE mX25519_Provider_Precomputed_scalarmult_base(VALUE self, VALUE scalar)
{
    /* X25519_KEY ensures inputs are aligned at 32-bytes */
    X25519_KEY raw_scalar, product;

    StringValue(scalar);
    if(RSTRING_LEN(scalar) != X25519_KEYSIZE_BYTES) {
        rb_raise(
            rb_eArgError,
            "expected %d-byte scalar, got %ld",
            X25519_KEYSIZE_BYTES,
            RSTRING_LEN(scalar)
        );
    }

    memcpy(raw_scalar, RSTRING_PTR(scalar), X25519_KEYSIZE_BYTES);
    x25519_precomputed_scalarmult_base(product, raw_scalar);

    return rb_str_new((const char *)product, X25519_KEYSIZE_BYTES);
}