Key restrictions

Enforced by default, as for the content encryption algorithms: RFC 9053 §6 makes the checks a MUST and the classes are new. alg, when present, must match the identifier; key_ops, when present, must include derive key or derive bits for the key of a derivation or an agreement, wrap key or encrypt to wrap and unwrap key or decrypt to unwrap, and "MUST be empty for the public key" of an agreement (§6.3.1). direct enforces nothing: the key is the content key itself, and the content encryption or MAC algorithm checks it when it uses it. withKeyRestrictionsEnforced(false), on an algorithm or through the Manager, turns it off; see Key restrictions for the mechanism.

use Cose\Algorithm\KeyManagement\A128KW;
use Cose\Algorithm\KeyManagement\Direct;
use Cose\Algorithm\KeyManagement\DirectHKDF_SHA256;
use Cose\Algorithm\KeyManagement\ECDH_ES_A128KW;
use Cose\Algorithm\KeyManagement\ECDH_ES_HKDF256;
use Cose\Algorithm\KeyManagement\ECDH_SS_HKDF256;
use Cose\Algorithm\Manager;

$manager = Manager::create()->add(
    Direct::create(),
    DirectHKDF_SHA256::create(),
    A128KW::create(),
    ECDH_ES_HKDF256::create(),
    ECDH_SS_HKDF256::create(),
    ECDH_ES_A128KW::create(),
);

The ecdh-direct-examples, ecdh-wrap-examples, hkdf-hmac-sha-examples, hkdf-aes-examples, aes-wrap-examples, X25519-tests and enveloped-tests fixtures of cose-wg/Examples, and the layered ones of RFC 8152 Appendix B and C.5.4, are opened by the test suite, every intermediate the generator recorded (COSE_KDF_Context, shared secret, KEK, CEK) compared on the way.