msrv 1.70

.github/workflows/test.yml

@@ -22,7 +22,7 @@ jobs:
     strategy:
       matrix:
         rust:
-          - 1.73.0 # MSRV
+          - 1.72.0  # MSRV is 1.70, but GA flaky
           - stable
         target:
           - thumbv7em-none-eabi
@@ -48,7 +48,7 @@ jobs:
         include:
           # 32-bit Linux
           - target: i686-unknown-linux-gnu
-            rust: 1.73.0 # MSRV
+            rust: 1.72.0  # MSRV is 1.70, but GA flaky
             deps: sudo apt update && sudo apt install gcc-multilib
           - target: i686-unknown-linux-gnu
             rust: stable
@@ -56,7 +56,7 @@ jobs:
 
           # 64-bit Linux
           - target: x86_64-unknown-linux-gnu
-            rust: 1.73.0 # MSRV
+            rust: 1.72.0  # MSRV is 1.70, but GA flaky
           - target: x86_64-unknown-linux-gnu
             rust: stable
     steps:
@@ -76,17 +76,17 @@ jobs:
         include:
           # ARM32
           - target: armv7-unknown-linux-gnueabihf
-            rust: 1.73.0 # MSRV (cross)
+            rust: 1.72.0  # MSRV is 1.70, but GA flaky
           - target: armv7-unknown-linux-gnueabihf
             rust: stable
           # ARM64
           - target: aarch64-unknown-linux-gnu
-            rust: 1.73.0 # MSRV (cross)
+            rust: 1.72.0  # MSRV is 1.70, but GA flaky
           - target: aarch64-unknown-linux-gnu
             rust: stable
           # PPC32
           - target: powerpc-unknown-linux-gnu
-            rust: 1.73.0 # MSRV (cross)
+            rust: 1.72.0 # MSRV (cross)
           - target: powerpc-unknown-linux-gnu
             rust: stable
     runs-on: ubuntu-latest

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "fips205"
-version = "0.1.1"
+version = "0.1.2"
 edition = "2021"
 license = "MIT OR Apache-2.0"
 description = "FIPS 205 (draft): Stateless Hash-Based Digital Signature Standard"

README.md

@@ -53,7 +53,7 @@ The Rust [Documentation][docs-link] lives under each **Module** corresponding to
 * This crate is fully functional and corresponds to the first initial public draft of FIPS 205.    
 * Constant-time assurances target the source-code level only, and are a work in progress.
 * Note that FIPS 205 places specific requirements on randomness per section 3.1, hence the exposed `RNG`.
-* Requires Rust **1.73** or higher due to `div_ceil()`. The minimum supported Rust version may be changed 
+* Requires Rust **1.70** or higher due to `div_ceil()`. The minimum supported Rust version may be changed 
 in the future, but it will be done with a minor version bump.
 * All on-by-default features of this library are covered by SemVer.
 * This software is experimental and still under active development -- USE AT YOUR OWN RISK!

src/helpers.rs

@@ -66,7 +66,7 @@ pub(crate) fn to_byte(x: u32, n: u32) -> [u8; ((crate::LEN2 * crate::LGW + 7) /
 /// Input: Byte string `X` of length at least `ceil(out_len·b/8)`, integer `b`, output length `out_len`. <br>
 /// Output: Array of `out_len` integers in the range `[0, . . . , 2^b − 1]`.
 pub(crate) fn base_2b(x: &[u8], b: u32, out_len: u32, baseb: &mut [u32]) {
-    debug_assert!(x.len() >= (out_len * b).div_ceil(8) as usize);
+    debug_assert!(x.len() >= ((out_len * b + 7) / 8) as usize);
     debug_assert!(b < 16); // Consider optimizing `baseb` output to be u16
     debug_assert_eq!(out_len as usize, baseb.len());
 

src/slh.rs

@@ -112,25 +112,25 @@ pub(crate) fn slh_sign_with_rng<
     let digest = (hashers.h_msg)(&r, &sk.pk_seed, &sk.pk_root, m);
 
     // 11: md ← digest[0 : ceil(k·a/8)]    ▷ first ceil(k·a/8) bytes
-    let index1 = (K::to_usize() * A::to_usize()).div_ceil(8);
+    let index1 = (K::to_usize() * A::to_usize() + 7) / 8;
     let md = &digest[0..index1];
 
     // 12: tmp_idx_tree ← digest[ceil(k·a/8) : ceil(k·a/8) + ceil((h-h/d)/8)]    ▷ next ceil((h-h/d)/8) bytes
-    let index2 = index1 + (H::to_usize() - H::to_usize() / D::to_usize()).div_ceil(8);
+    let index2 = index1 + (H::to_usize() - H::to_usize() / D::to_usize() + 7) / 8;
     let tmp_idx_tree = &digest[index1..index2];
 
     // 13: tmp_idx_leaf ← digest[ceil(k·a/8) + ceil((h-h/d)/8) : ceil(k·a/8) + ceil((h-h/d)/8) + ceil(h/8d)]    ▷ next ceil(h/8d) bytes
-    let index3 = index2 + H::to_usize().div_ceil(8 * D::to_usize());
+    let index3 = index2 + (H::to_usize() + 8 * D::to_usize() - 1) / (8 * D::to_usize());
     let tmp_idx_leaf = &digest[index2..index3];
 
     // 14:
     // 15: idx_tree ← toInt(tmp_idx_tree, ceil((h-h/d)/8)) mod 2^{h−h/d}
     let idx_tree =
-        helpers::to_int(tmp_idx_tree, (H::to_u32() - H::to_u32() / D::to_u32()).div_ceil(8))
+        helpers::to_int(tmp_idx_tree, (H::to_u32() - H::to_u32() / D::to_u32() + 7) / 8)
             & (u64::MAX >> (64 - (H::to_u32() - H::to_u32() / D::to_u32())));
 
     // 16: idx_leaf ← toInt(tmp_idx_leaf, ceil(h/8d) mod 2^{h/d}
-    let idx_leaf = helpers::to_int(tmp_idx_leaf, H::to_u32().div_ceil(8 * D::to_u32()))
+    let idx_leaf = helpers::to_int(tmp_idx_leaf, (H::to_u32() + 8 * D::to_u32() - 1) / (8 * D::to_u32()))
         & (u64::MAX >> (64 - H::to_u32() / D::to_u32()));
 
     // 17:
@@ -210,25 +210,25 @@ pub(crate) fn slh_verify<
     let digest = (hashers.h_msg)(r, &pk.pk_seed, &pk.pk_root, m);
 
     // 10: md ← digest[0 : ceil(k·a/8)]    ▷ first ceil(k·a/8) bytes
-    let index1 = (K::to_usize() * A::to_usize()).div_ceil(8);
+    let index1 = (K::to_usize() * A::to_usize() + 7) / 8;
     let md = &digest[0..index1];
 
     // 11: tmp_idx_tree ← digest[ceil(k·a/8) : ceil(k·a/8) + ceil((h - h/d)/8)]     ▷ next ceil((h - h/d)/8) bytes
-    let index2 = index1 + (H::to_usize() - H::to_usize() / D::to_usize()).div_ceil(8);
+    let index2 = index1 + (H::to_usize() - H::to_usize() / D::to_usize() + 7) / 8;
     let tmp_idx_tree = &digest[index1..index2];
 
     // 12: tmp_idx_leaf ← digest[ceil(k·a/8) + ceil((h - h/d)/8) : ceil(k·a/8) + ceil((h - h/d)/8) + ceil(h/8d)]  ▷ next ceil(h/8d) bytes
-    let index3 = index2 + H::to_usize().div_ceil(8 * D::to_usize());
+    let index3 = index2 + (H::to_usize() + 8 * D::to_usize() - 1) / (8 * D::to_usize());
     let tmp_idx_leaf = &digest[index2..index3];
 
     // 13:
     // 14: idx_tree ← toInt(tmp_idx_tree, ceil((h - h/d)/8)) mod 2^{h−h/d}
     let idx_tree =
-        helpers::to_int(tmp_idx_tree, (H::to_u32() - H::to_u32() / D::to_u32()).div_ceil(8))
+        helpers::to_int(tmp_idx_tree, (H::to_u32() - H::to_u32() / D::to_u32() + 7) /8)
             & (u64::MAX >> (64 - (H::to_u32() - H::to_u32() / D::to_u32())));
 
     // 15: idx_leaf ← toInt(tmp_idx_leaf, ceil(h/8d) mod 2^{h/d}
-    let idx_leaf = helpers::to_int(tmp_idx_leaf, H::to_u32().div_ceil(8 * D::to_u32()))
+    let idx_leaf = helpers::to_int(tmp_idx_leaf, (H::to_u32() + 8 * D::to_u32() - 1) / (8 * D::to_u32()))
         & (u64::MAX >> (64 - H::to_u32() / D::to_u32()));
 
     // 16:

src/wots.rs

@@ -148,7 +148,7 @@ pub(crate) fn wots_sign<K: ArrayLength, LEN: ArrayLength, M: ArrayLength, N: Arr
 
     // 10: msg ← msg ∥ base_2^b(toByte(csum, ceil(len2·lgw/8)), lgw, len2)    ▷ Convert csum to base w
     helpers::base_2b(
-        &helpers::to_byte(csum, (crate::LEN2 * crate::LGW).div_ceil(8)),
+        &helpers::to_byte(csum, (crate::LEN2 * crate::LGW + 7) / 8),
         crate::LGW,
         crate::LEN2,
         &mut msg[(2 * N::to_usize())..],
@@ -223,7 +223,7 @@ pub(crate) fn wots_pk_from_sig<K: ArrayLength, LEN: ArrayLength, M: ArrayLength,
 
     // 10: msg ← msg ∥ base_2^b(toByte(csum, ceil(len2·lgw/8)), lgw, len2)    ▷ Convert csum to base w
     helpers::base_2b(
-        &helpers::to_byte(csum, (crate::LEN2 * crate::LGW).div_ceil(8)),
+        &helpers::to_byte(csum, (crate::LEN2 * crate::LGW + 7) / 8),
         crate::LGW,
         crate::LEN2,
         &mut msg[(2 * N::to_usize())..],