Adam Wick
fa872c951a
Previously, we used a little bit of generation to drive a lot of Rust macros. This works, but it's a little confusing to read and write. In addition, we used a lot of implementations with variable timings based on their input, which isn't great for crypto. This is the start of an attempt to just generate all of the relevant Rust code directly, and to use timing-channel resistant implementations for most of the routines.
66 lines
1.8 KiB
Rust
66 lines
1.8 KiB
Rust
pub trait SquareRoot {
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/// Compute the integer square root of the given value. The integer square
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/// root is the value Z such that the real root R satisfies Z <= R < Z+1.
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fn sqrt(&self) -> Self;
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}
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macro_rules! sqrt_impls
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{
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($name: ident) => {
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impl SquareRoot for $name {
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fn sqrt(&self) -> Self {
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let mut num = self.clone();
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let mut res = $name::zero();
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let mut bit = $name::from(1u64) << ($name::bit_length() - 2);
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while bit > num {
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bit >>= 2;
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}
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while !bit.is_zero() {
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let mut resbit = res.clone();
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resbit += &bit;
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if num >= resbit {
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num -= resbit;
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res += &bit << 1;
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}
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res >>= 1;
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bit >>= 2;
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}
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res
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}
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}
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}
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}
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#[cfg(test)]
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macro_rules! generate_sqrt_tests {
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($name: ident, $lname: ident) => {
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#[test]
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fn $lname() {
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generate_sqrt_tests!(body $name, $lname);
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}
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};
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(ignore $name: ident, $lname: ident) => {
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#[test]
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#[ignore]
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fn $lname() {
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generate_sqrt_tests!(body $name, $lname);
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}
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};
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(body $name: ident, $lname: ident) => {
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let fname = build_test_path("sqrt", stringify!($name));
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run_test(fname.to_string(), 2, |case| {
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let (neg0, abytes) = case.get("a").unwrap();
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let (neg1, rbytes) = case.get("r").unwrap();
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assert!(!neg0 && !neg1);
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let a = $name::from_bytes(abytes);
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let r = $name::from_bytes(rbytes);
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assert_eq!(r, a.sqrt());
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});
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};
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} |