Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

[otbn/rsa] Add SCA hardening for sel_sqr_or_sqrmul #25300

Closed
wants to merge 1 commit into from
Closed

[otbn/rsa] Add SCA hardening for sel_sqr_or_sqrmul #25300

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
33 changes: 24 additions & 9 deletions sw/otbn/crypto/modexp.s
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -27,24 +27,39 @@
* @param[in] x9: pointer to temp reg, must be set to 3
* @param[in] x11: pointer to temp reg, must be set to 2
*
* clobbered registers: x8, x21, w0, w2
* clobbered registers: x8, x21, x22, x23, w0, w2, w3
* clobbered Flag Groups: none
*/
sel_sqr_or_sqrmul:
/* read FG0.C and add 2, x22 is a pointer to w3 if FG0.C == 1 else w2 */
csrrs x22, FG0, x0
andi x22, x22, 1
addi x22, x22, 2
/* iterate over all limbs */
loop x30, 4
loop x30, 10
/* read single random bit */
csrrs x23, URND, x0
andi x23, x23, 1
/* randomly change WDRs */
xor x22, x22, x23
xor x9, x9, x23
xor x11, x11, x23

/* load limb from dmem */
bn.lid x9, 0(x21)
bn.lid x11, 0(x21)

/* load limb from regfile buffer */
bn.movr x11, x8++
/* randomize dmem with random number from URND */
bn.wsrr w0, URND
bn.sid x0, 0(x21)

/* conditional select: w0 = FG0.C?w[x8+i]:dmem[x21+i] */
bn.sel w0, w2, w3, C
/* load limb from regfile buffer */
bn.movr x9, x8++

/* store selected limb to dmem */
bn.sid x0, 0(x21++)

bn.sid x22, 0(x21++)
/* restore clobbered x9, x11 */
li x9, 3
li x11, 2
ret


Expand Down
Loading