# BadEncKeyLen (/docs/errors/chain/BadEncKeyLen)

The `enc_key` passed to `announce_next_key` is not the exact ML-KEM-768 encapsulation key length (1184 bytes). Check the byte length of the `enc_key` argument before announcing.

Declared by the `MevShield` pallet; it classifies to the semantic code [`invalid_argument`](/docs/errors/invalid-argument).

## Remediation [#remediation]

Check the argument values against the operation schema

The same explanation is available in the terminal: `btcli explain BadEncKeyLen`.