The SubtleCrypto.exportKey() method returns a Promise of the key encrypted in the requested format. If the key is not extractable, that is if CryptoKey.extractable returns false, the promise fails with an InvalidAccessError exception; it the format is unknown, the promive fails with a NotSupported exception.
The SubtleCrypto.generateKey() method returns a Promise of a newly generated CryptoKey, for symmetrical algorithms, or a CryptoKeyPair, containing two newly generated keys, for asymmetrical algorithm, that matches the algorithm, the usages and the extractability given as parameters.
The SubtleCrypto.wrapKey() method returns a Promise of a wrapped symmetric key for usage (transfer, storage) in unsecure environments. The wrapped buffer returned is in the format given in parameters, and contained the key wrapped by the give wrapping key with the given algorithm.