DROP KEY

Drop a current key from a database.

DROP KEY [ IF EXISTS ] key CASCADE
IF EXISTS
Do not return a warning if the key does not exist.
key
A current key name created with the CREATE KEY command.
Note: You must be the owner of a key to drop it.
CASCADE
This parameter is required but currently has no effect.

Note that the DROP KEY operation is non-transactional and will error out when run inside a transaction block.

See also Encrypting Sensitive Data.

For example:
premdb=# drop key ybd100key cascade; 
DROP KEY
If a user who is not the owner of a key attempts to drop it, they will receive the following error message: 
premdb=# drop key yb100key cascade;
ERROR:  must be owner of key yb100key