Apple-2gs-SW/65816-crypto
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Small decryption optimization, saving a value in a register between rounds.

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This commit is contained in:
Stephen Heumann 2017-06-27 22:35:57 -05:00
parent 634ff1e865
commit e46264f0c4
1 changed files with 21 additions and 10 deletions
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31
aes.macros
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@ -244,17 +244,19 @@
&out setc state2
.cont
InvMixColumn 12,1,6,11,12
InvMixColumn 12,1,6,11,12,1
InvMixColumn 0,5,10,15,0
InvMixColumn 4,9,14,3,4
InvMixColumn 8,13,2,7,8
InvMixColumn 4,9,14,3,4,dotax=1
mend
macro
InvMixColumn &A,&B,&C,&D,&i
InvMixColumn &A,&B,&C,&D,&i,&skipldx,&dotax
aif C:&skipldx,.skip
ldx &state+&i+2
.skip
lda Xtime9,X
ldy &state+&i+0
eor XtimeB,Y
@ -301,12 +303,17 @@
tay
lda InvSbox,Y
eor rk+(&round-1)*16+&C
aif (C:&dotax).AND.(&round<>1),.dotax
sta &out+&C
ago .done
.dotax
tax
.done
mend
macro
InvFinalRoundStep &to,&from
InvFinalRoundStep &to,&from,&dotax
lda state1+&from
aif (rk+&round*16+&from)>255,.bigindex
@ -326,8 +333,12 @@
ldx #(&round-1)*16+&to
eor rk,X
.cont2
aif C:&dotax,.dotax
sta state2+&to
ago .done
.dotax
tax
.done
mend
@ -344,15 +355,15 @@
InvFinalRoundStep 9,5
InvFinalRoundStep 5,1
InvFinalRoundStep 10,2
InvFinalRoundStep 2,10
InvFinalRoundStep 14,6
InvFinalRoundStep 6,14
InvFinalRoundStep 15,3
InvFinalRoundStep 3,7
InvFinalRoundStep 7,11
InvFinalRoundStep 11,15
InvFinalRoundStep 2,10
InvFinalRoundStep 10,2
InvFinalRoundStep 6,14
InvFinalRoundStep 14,6,1
mend