DS1963S

23 of 37

Device Flag Summary Table 3

Command, Function or Condition

HIDE

CHLG

AUTH

MATCH

Return to Probe Condition

SET

-----

-----

-----

Read Memory Command

-----

CLEARED

CLEARED

-----

Match Scratchpad Command

-----

CLEARED

CLEARED

Note 1)

Write Scratchpad Command

-----

CLEARED

CLEARED

-----

Read Scratchpad Command

-----

-----

-----

-----

Erase Scratchpad Command

CLEARED

CLEARED

CLEARED

-----

Copy Scratchpad Command

-----

CLEARED

CLEARED

-----

Read Authenticated Page Command

-----

CLEARED

CLEARED

-----

Validate Data Page Function

SET

CLEARED

CLEARED

-----

Sign Data Page Function

-----

CLEARED

CLEARED

-----

Compute Challenge Function

-----

SET

CLEARED

CLEARED

Authenticate Host Function

SET

CLEARED

Note 2)

CLEARED

Compute first Secret Function

SET

CLEARED

CLEARED

CLEARED

Compute next Secret Function

SET

CLEARED

CLEARED

CLEARED

1) The flag is SET if the data matches and the AUTH flag was set before command execution;

otherwise the flag is CLEARED. Setting the MATCH flag requires the successful execution of

Compute Challenge, Authenticate Host and Match Scratchpad in an uninterrupted sequence.

2) Is SET only if CHLG flag was set before command execution; otherwise is cleared.

SHA-1 COMPUTATION ALGORITHM

This description of the SHA computation is adapted from the Secure Hash Standard SHA-1 document

referenced on page 2 of this data sheet. The algorithm takes as its input data 16, 32-bit words Mt (0 £ t £

15), as shown in Table 2, SHA-1 Input Message Formats. The SHA computation involves a sequence of

eighty 32-bit words called Wt (0 £ t £ 79), a sequence of eighty 32-bit words called Kt (0 £ t £ 79), a

Boolean function ft (B, C, D) (0 £ t £ 79) with B, C and D being 32-bit words, and three more 32-bit

words called A, E and TMP. The operations required for the SHA computation are arithmetic addition

without carry (“+”), logical inversion or 1’s complement (“\”), EXCLUSIVE OR (“

Å”), logical AND

(“

Ù”), logical OR (“Ú”), assignment (“:=”), and circular shifting within a 32-bit word. The expression

“Sn(X)” represents a circular shift of X by n positions to the left, with X being a 32-bit word.

The function ft is defined as follows:

ft(B,C,D) = (B Ù C) Ú ((B\) Ù D)

(0

£ t £ 19)

B

Å C Å D

(20

£ t £ 39)

(B

Ù C) Ú (B Ù D) Ú (C Ù D)

(40

£ t £ 59)

B

Å C Å D

(60

£ t £ 79)

The sequence Wt (0 £ t £ 79) is defined as follows:

Wt := Mt

(0

£ t £ 15)

S1(Wt-3 Å Wt-8 Å Wt-14 Å Wt-16)

(16

£ t £ 79)