DS1961S

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required. For practical use of the DS1961S as a monetary token, partial secrets are more critical than

being able to write-protect the secret or other areas of the device.

Table 3b. SHA-1 INPUT DATA FOR COPY SCRATCHPAD COMMAND WHEN

COPYING TO THE REGISTER PAGE OR SECRET

M0[31:24] = (SS + 0)

M0[23:16] = (SS + 1)

M0[15:8] = (SS + 2)

M0[7:0] = (SS + 3)

M1[31:24] = (SS + 0)

M1[23:16] = (SS + 1)

M1[15:8] = (SS + 2)

M1[7:0] = (SS + 3)

M2[31:24] = (SS + 4)

M2[23:16] = (SS + 5)

M2[15:8] = (SS + 6)

M2[7:0] = (SS + 7)

M3[31:24] = (RP + 0)

M3[23:16] = (RP + 1)

M3[15:8] = (RP + 2)

M3[7:0] = (RP + 3)

M4[31:24] = (RP + 4)

M4[23:16] = (RP + 5)

M4[15:8] = (RP + 6)

M4[7:0] = (RP + 7)

M5[31:24] = (ID + 0)

M5[23:16] = (ID + 1)

M5[15:8] = (ID + 2)

M5[7:0] = (ID + 3)

M6[31:24] = (ID + 4)

M6[23:16] = (ID + 5)

M6[15:8] = (ID + 6)

M6[7:0] = (ID + 7)

M7[31:24] = FFh

M7[23:16] = FFh

M7[15:8] = FFh

M7[7:0] = FFh

M8[31:24] = (SP + 0)

M8[23:16] = (SP + 1)

M8[15:8] = (SP + 2)

M8[7:0] = (SP + 3)

M9[31:24] = (SP + 4)

M9[23:16] = (SP + 5)

M9[15:8] = (SP + 6)

M9[7:0] = (SP + 7)

M10[31:24] = MP

M10[23:16] = (ID + 0) M10[15:8] = (ID + 1)

M10[7:0] = (ID + 2)

M11[31:24] = (ID + 3) M11[23:16] = (ID + 4) M11[15:8] = (ID + 5)

M11[7:0] = (ID + 6)

M12[31:24] = (SS + 4) M12[23:16] = (SS + 5) M12[15:8] = (SS + 6)

M12[7:0] = (SS + 7)

M13[31:24] = FFh

M13[23:16] = FFh

M13[15:8] = FFh

M13[7:0] = 80h

M14[31:24] = 00h

M14[23:16] = 00h

M14[15:8] = 00h

M14[7:0] = 00h

M15[31:24] = 00h

M15[23:16] = 00h

M15[15:8] = 01h

M15[7:0] = B8h

Legend

Mt

Input Buffer of SHA Engine

0

£ t £ 15; 32-Bit Words

(SS + N)

Byte N of Secret; Secret Begins at Address 0080h

(see Memory Map)

(RP + N) Byte N of Register Page; Page Begins at 0088h

(see Memory Map)

(SP + N) Byte N of Scratchpad

MP

MP[7:0] = 04h

(ID + N)

Byte N of Identity Register

Read Authenticated Page [A5h]

The read authenticated page command provides the master with the data of a full or partial memory page

plus a MAC. The MAC allows the master to determine whether the secret stored in the DS1961S is valid

within the application. The DS1961S computes the MAC from its secret, all the data of the selected

memory page, the first seven bytes of the identity register and a 3-byte challenge, which the master

should write to the scratchpad prior to issuing the read authenticated page command. To do this, the

master can use the write scratchpad command with any target address within the data memory. The

data that happens to reside in the scratchpad from a previous command as a challenge. The 160-bit MAC

is transmitted in the same way as with the copy scratchpad command, Table 2, but the data flows from the

DS1961S to the master. The data input to the SHA engine as it applies to the read authenticated page

command is shown in Table 4.