Function verify_cert 

pub fn verify_cert(
    master_public_key_hex: &str,
    version: &str,
    public_key_hex: &str,
    cert_hex: &str,
) -> Result<bool>

Verify that cert_hex is a valid master signature over cert_payload(version, public_key_hex). The platform performs the equivalent check in TypeScript; this Rust copy backs the round-trip tests and documents the exact bytes.