true when NativeCrypto routes BLS12-381 through the native blst backend;
false when it falls back to the portable bls12_381 trait default (e.g.
zkVM guest builds). Differential tests assert this so they fail loudly
instead of silently comparing the pure-Rust backend to itself.
true when NativeCrypto routes secp256r1_verify through the native
aws-lc-rs backend; false when it falls back to the portable p256 trait
default (e.g. zkVM guest builds). Differential tests assert this so they
fail loudly instead of silently comparing the pure-Rust backend to itself.