0 1 2 3 4 0 1 0 1 2 Secure Write Response Model (DRAFT 1) Include a digital signature over the response Used in conjunction with a Secure Write Request Algorithm Algorithm used to compute the digital signature For future proof NONE No digital signature For test purposes only AES-GMAC-64 64 bit AES signature algorithm is used ECC-256 256 bit ECC signature algorithm is used Status Status of last write operation SUCCESS Operation succeeded DS Operation failed digital signature check The signature was not valid ACL Operation failed access control check One or more registers were not writable by this role OFF Operation failed offset check Offset out of range or missing from multi-register value VAL Operation failed valid value check Value is out of acceptable range DS Digital Signature The DS covers all registers from X to N and is N registers in length Request Sequence Sequence number from the request Sequence Sequence number of response Shall be advanced for each response Timestamp Timestamp value is the number of seconds since January 1, 2000 Milliseconds Millisecond counter 0-999 Alarm Bitmask alarm code NONE No Alarms ALARM Security Alarm Tampered N Number of registers comprising the digital signature. The value of N must be at least 4 (64 bits)