Files
alttpr-baserom/decryption.asm
cassidoxa 788cceaab9 Continue labeling and documentation in ram.asm, main rando block
Deleted several unused modules and some commented code
Reorganized some routines to clean up modules
Moved some memory into mirrored WRAM
Refactored NMI hook aux routine
Removed old fake flipper fix
2022-11-16 21:38:28 -05:00

88 lines
2.5 KiB
NASM

;--------------------------------------------------------------------------------
LoadStaticDecryptionKey:
PHB : PHA : PHX : PHY : PHP
REP #$30 ; set 16-bit accumulator & index registers
LDX.w #StaticDecryptionKey ; Source
LDY.w #KeyBase ; Target
LDA.w #$000F ; Length
MVN $307F
PLP : PLY : PLX : PLA : PLB
RTL
;--------------------------------------------------------------------------------
;--------------------------------------------------------------------------------
RetrieveValueFromEncryptedTable:
;Requires 16-bit A and X/Y
;$00-$02 are long address of start of table
;A is desired byte offset into table
;Returns result in A
PHX : PHY
PHA
LDY.b Scrap04 : PHY : LDY.b Scrap06 : PHY : LDY.b Scrap08 : PHY
LDY.b Scrap0A : PHY : LDY.b Scrap0C : PHY : LDY.b Scrap0E : PHY
AND.w #$FFF8 : TAY
LDA.b [$00], Y : STA.l CryptoBuffer : INY #2
LDA.b [$00], Y : STA.l CryptoBuffer+2 : INY #2
LDA.b [$00], Y : STA.l CryptoBuffer+4 : INY #2
LDA.b [$00], Y : STA.l CryptoBuffer+6
LDA.w #$0002 : STA.b Scrap04 ;set block size
JSL.l XXTEA_Decode
PLA : STA.b Scrap0E : PLA : STA.b Scrap0C : PLA : STA.b Scrap0A
PLA : STA.b Scrap08 : PLA : STA.b Scrap06 : PLA : STA.b Scrap04
PLA : AND.w #$0007 : TAX
LDA.l CryptoBuffer, X
PHA
LDA.w #$0000
STA.l CryptoBuffer
STA.l CryptoBuffer+2
STA.l CryptoBuffer+4
STA.l CryptoBuffer+6
PLA
PLY : PLX
RTL
;--------------------------------------------------------------------------------
ChestData = $01E96C
ChestDataPayload = $01EABC ; ChestData+$0150
;--------------------------------------------------------------------------------
GetChestData:
LDA.l IsEncrypted : BNE .encrypted
INC.b Scrap0E : LDX.w #$FFFD ; what we wrote over
JML.l Dungeon_OpenKeyedObject_nextChest
.encrypted
INC.b Scrap0E : LDX.w #$FFFE
.nextChest
INX #2 : CPX.w #$0150 : BEQ .couldntFindChest
LDA.l ChestData, X : AND.w #$7FFF : CMP.b RoomIndex : BNE .nextChest
DEC.b Scrap0E : BNE .nextChest
LDA.b Scrap00 : PHA : LDA.b Scrap02 : PHA
LDA.w #ChestDataPayload : STA.b Scrap00
LDA.w #ChestDataPayload>>16 : STA.b Scrap02
TXA : LSR
JSL RetrieveValueFromEncryptedTable
STA.b Scrap0C
PLA : STA.b Scrap02 : PLA : STA.b Scrap00
LDA.l ChestData, X : ASL A : BCC .smallChest
JML.l Dungeon_OpenKeyedObject_bigChest ;(bank01.asm line #13783)
.smallChest
JML.l Dungeon_OpenKeyedObject_smallChest
.couldntFindChest
JML.l Dungeon_OpenKeyedObject_couldntFindChest
;--------------------------------------------------------------------------------