powPublic
Returns x^e (mod m), assuming that the exponent is public.
The function remains constant time with respect to x.
Function parameters
Parameters
An unsigned big integer with a fixed maximum size (`max_bits`), suitable for cryptographic operations.
Functions
Error sets in this namespace
Error Sets
- OverflowError
- Value is too large for the destination.
- InvalidModulusError
- Invalid modulus.
- NullExponentError
- Exponentiation with a null exponent.
- FieldElementError
- Invalid field element for the given modulus.
- RepresentationError
- Invalid representation (Montgomery vs non-Montgomery domain.)
- Error
- The set of all possible errors `std.crypto.ff` functions can return.
Source
Implementation
pub fn powPublic(self: Self, x: Fe, e: Fe) NullExponentError!Fe {
var e_normalized = Fe{ .v = e.v.normalize() };
var buf_: [Fe.encoded_bytes]u8 = undefined;
var buf = buf_[0 .. math.divCeil(usize, e_normalized.v.limbs_len * t_bits, 8) catch unreachable];
e_normalized.toBytes(buf, .little) catch unreachable;
const leading = @clz(e_normalized.v.limbsConst()[e_normalized.v.limbs_len - carry_bits]);
buf = buf[0 .. buf.len - leading / 8];
return self.powWithEncodedPublicExponent(x, buf, .little);
}