gipu/polictf/asms/decrypt.pstc

def datastrlen:
###############
# r0 = offset of str in data
# retval (r0) = strlen
###############
push r1
push r2
push r3
movr s2, r0
movi s1, 0
lodr s0, s2
cmpb s0, 0
jpei exit
loop:
movi s2, 0
addi s1, 1
addr s2, s1
lodr s0, s2
cmpb s0, 0
jpni loop
exit:
movr r0, s1
poop r3
poop r2
poop r1
retn

def round: # round(uint16_t text[2])
#################
# r0 = offset of text[0] in data
# r1 = offset of text[1] in data
# r2 = text[0]
# r3 = text[1]
# retval = void
################
push r1
push r2
push r3
lodr r2, r0 # text[0]
lodr r3, r1 # text[1]
movi s0, 0 # i
movi s1, 0 # sum
loop:
push s0 # saving i
# s0 and s1 will be used as tmps
#########
# calc v1
#########
movr s0, r2
shli s0, 4
addi s0, 0x7275 # s0 = (text[0] << 4) + k2
movr s1, r2
xorr s0, s1 # s0 = ((text[0] << 4) + k2) ^ text[0]
push s0
movr s0, r2
shri s0, 5
addi s0, 0x6e73 # s0 = (text[0] >> 5) + k3
poop s1
xorr s0, s1 # s0 = ((text[0] << 4) + k2) ^ text[0] ^ ((text[0] >> 5) + k3)
subr r3, s0 # r3 -= s0
#########
# calc v0
#########
movr s0, r3
shli s0, 4
addi s0, 0x7065 # s0 = (text[1] << 4) + k0
movr s1, r3
xorr s0, s1 # s0 = ((text[1] << 4) + k0) ^ text[1]
push s0
movr s0, r3
shri s0, 5
addi s0, 0x7065 # s0 = (text[1] >> 5) + k1
poop s1
xorr s0, s1 # s0 = ((text[1] << 4) + k0) ^ text[1] ^ ((text[1] >> 5) + k1)
subr r2, s0 # r2 -= s0
######
# end loop
#####
poop s0 # restoring i
addi s0, 1
cmpb s0, 127 # while (i < 128)
jpbi loop
# saving the values
strr r0, r2
strr r1, r3
poop r3
poop r2
poop r1
retn

def main:
movi r0, 0
call datastrlen
movr r2, r0
movi s0, 0
decrypt:
push s0
movi r0, 0
movi r1, 2
addr r0, s0
addr r1, s0
call round
poop s0
addi s0, 4
cmpr s0, r2
jpbi decrypt
shit