SHA - SHA256 Digest

The SHA command utilizes the SHA256 Hash algorithm for computing the hash of a message. The primary input to the command is the actual message. The message is submitted to the device in blocks of 1 to 64 bytes. The following procedure is used when no context switching is required:

1.Issue the SHA command in Start mode. No message is included.
2.Issue the SHA command in Update mode with 1 to 64 bytes of the message.
3.Repeat step 2 until the total number of bytes of the message have been submitted.
4.Issue the SHA command in End mode to complete the SHA256 calculation.

Table 1. Input Parameters SHA Standard Mode
Opcode (1 Byte)	Mode (1 Byte)	Param2 (2 Bytes)	Data (Varies by Mode)	Description
0x47	0x00	0x00 00	0 bytes	Start mode
	0x01	0x00 [ByteCount]	1 to 64 bytes	Update mode
	0x02	0x00 [ByteCount]	0 to 64 bytes	Finalize mode: Digest placed in Output Buffer and TempKey
	0x42	0x00 [ByteCount]		Finalize mode: Digest placed in Output Buffer and Message Digest Buffer
	0xC2	0x00 [ByteCount]		Finalize mode: Digest placed in Output Buffer only

Table 2. Output Response SHA256 Standard
Name	Mode	Size	Description
Response	0x00, 0x01	1 byte	0x00 if successful, otherwise an error code is received
Response	0x02, 0x42, 0xC2	1 byte 32 bytes	If error code SHA256 Digest