An envelope signed OUTSIDE this crate, the way the owner's signers sign: openssl dgst -sha256 -sign over the DSSE PAE gives the same ASN.1 DER ECDSA signature a YubiKey's PIV slot returns (yubico-piv-tool -a sign, cosign --sk). cosign verify-blob-attestation --key release-test.pub --signature release.intoto.jsonl --type https://slsa.dev/provenance/v1 --insecure-ignore-tlog=true art.bin says Verified OK (cosign v3.1.3, 2026-10-29). The private key was a throwaway and is not kept.