The UMAC-32 algorithm requires, in addition to the key, a nonce byte
array. The byte array must be 1-16 bytes of random data, which is
passed to the init method of IMac in the attributes map.
UMac32 defined an additional key for this map:
| java.lang.String NONCE_MATERIAL | Variable |
| The key for the nonce material for the attributes map. The value mapped must be a byte array of size 1-16 bytes. |