pkc%fix(bls): read legacy BLS keys and signatures as the reference implementation does

pkgs/pkc/CHANGELOG.md

@@ -7,6 +7,21 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 
 ## [Unreleased]
 
+### Added
+
+- `BlsScheme::is_canonical_pk` and `BlsScheme::is_canonical_sig`, each scheme's rule for `is_canonical::<S>()`.
+- `BlsScheme::g1_bytes` and `BlsScheme::g2_bytes`, each scheme's byte layout of a point; `BlsScheme::pk_ietf_bytes`,
+  the IETF compressed form of a G1 encoding in that layout, and `BlsScheme::sig_ietf_x_bytes`, the `x` of a G2
+  encoding in the IETF compressed layout with the sign bit clear.
+
+### Changed
+
+- `BlsPkBytes::to::<BlsScChia>()` and `BlsPublicKey::<BlsScChia>::from_bytes` read `x = 0` with the sign bit set,
+  (0, -2), as the reference implementation does.
+- `is_canonical::<BlsScChia>()` on `BlsPkBytes` and `BlsSigBytes` accepts legacy encodings of an `x` with no point on
+  the curve, as the reference implementation does; for signatures, only with the sign bit clear. `to::<BlsScChia>()`
+  still refuses them, having no point to return.
+
 ## [0.2.0-beta] - 2026-10-20
 
 ### Added

pkgs/pkc/contrib/README.md

@@ -10,6 +10,7 @@ serialization and hashing, and commitment hash function, apart from fixed inputs
 | `bls_ies.json5` | `gen_ies.cpp` |
 | `bls_keygen.json5` | `gen_keygen.cpp` |
 | `bls_llmq_100.json5` | `gen_llmq_100.cpp` |
+| `bls_read.json5` | `gen_read.cpp` |
 | `bls_secure_aggregate.json5` | `gen_secure_aggregate.cpp` |
 | `bls_serialize.json5` | `gen_serialize.cpp` |
 | `bls_sign.json5` | `gen_sign.cpp` |
@@ -20,6 +21,8 @@ inputs, which the program checks against the commitment hash it computes. For `b
 legacy map's hashing and reduction steps with relic, which the library does not expose, and the library's own point
 anchors them.
 
+`bls_read.json5` records how the library reads key and signature bytes under each scheme, as `gen_read.cpp` describes.
+
 ## Regenerating
 
 `regen.py` needs Python 3.11.4 or later, git, CMake, a C compiler, a C++20 compiler, Boost and GMP, all of which the