An array of strings identifying the operations for which the key may be used.

The possible usages are:

• 'encrypt' - The key may be used to encrypt data.
• 'decrypt' - The key may be used to decrypt data.
• 'sign' - The key may be used to generate digital signatures.
• 'verify' - The key may be used to verify digital signatures.
• 'deriveKey' - The key may be used to derive a new key.
• 'deriveBits' - The key may be used to derive bits.
• 'wrapKey' - The key may be used to wrap another key.
• 'unwrapKey' - The key may be used to unwrap another key.

Valid key usages depend on the key algorithm (identified by cryptokey.algorithm.name).