KeyUsage ::= BIT STRING {
     digitalSignature        (0),
     nonRepudiation          (1),  -- recent editions of X.509 have
                                -- renamed this bit to contentCommitment
     keyEncipherment         (2),
     dataEncipherment        (3),
     keyAgreement            (4),
     keyCertSign             (5),
     cRLSign                 (6),
     encipherOnly            (7),
     decipherOnly            (8) }