Sign - Internal Message

The Sign command in the Internal Message mode is used to sign a message that was internally generated. The command calculates the internal message digest and then signs the digest using the ECDSA sign algorithm with the private ECC key specified in KeyID. Internally generated messages must always reside in TempKey. The value in TempKey must be generated using either the GenDig or the GenKey command. If TempKey is not valid an error will occur. Typical uses include:

Signing an internally generated random key. This is typically generated by the GenKey command.
The output of a GenKey or GenDig commands, provided the output is located in TempKey.

For the ATECC608A-TFLXTLS device, only Slot 1 is capable of signing internally generated messages.

Table 1. Input Parameters - Sign Internal Message
Opcode (1 Byte)	Mode (1 Byte)	KeyId (2 Bytes)	Description
0x41	0x00 or 0x20	0x00 0[Slot]	Serial number is not included in the message digest calculation
0x41	0x40 or 0x60	0x00 0[Slot]	Serial number is included in the message digest calculation

Table 2. Output Response - Sign Internal Message
Name	Size	Description
Response	1 byte	Error code if the command fails
Response	64 bytes	The signature composed of R and S values

Internal Message Generation

The internal message is generated based on a 55 Byte Field as shown below.

Byte Count	Serial Number Not Included	Serial Number Included
32 bytes 1 byte 1 byte 2 bytes 2 bytes 2 bytes 1 byte 2 bytes 1 byte 4 bytes 2 bytes 2 bytes 1 byte 1 byte 1 byte	TempKey⁽¹⁾ Opcode Mode KeyID SlotConfig (of TempKeyFlags.KeyID) KeyConfig (of TempKeyFlags.KeyID) TempKeyFlags⁽²⁾ Zeros SN[8] = 0x01 Zeros SN[0:1] = 0x01 0x23 Zeros SlotLocked:TempKeyFlags.KeyID 0x00 0x00	TempKey⁽¹⁾ Opcode Mode KeyID SlotConfig (of TempKeyFlags.KeyID) KeyConfig (of TempKeyFlags.KeyID) TempKeyFlags⁽²⁾ Zeros SN[8] = 0x01 SN[4:7] SN[0:1] = 0x01 0x23 SN[2:3] SlotLocked:TempKeyFlags.KeyID 0x00 0x00

Notes:

1. TempKey must be generated by GenKey or GenDig commands prior to this calculation.
2.TempKeyFlags Consists of: (b[7]: NoMacFlag, b[6]: GenKeyData, b[5]: GenDigData, b[4]: SourceFlag,b[3:0] TempKeyFlags)