Fix the python code for aes$/$s$-$aes. s$\_$box $=[$

$[0$x$09,0$x$04,0$x$0$A$,0$x$0$D$],$

$[0$x$0$D$,0$x$09,0$x$04,0$x$0$A$],$

$[0$x$0$A$,0$x$0$D$,0$x$09,0$x$04],$

$[0$x$04,0$x$0$A$,0$x$0$D$,0$x$09]$

$]$

# Fixed $8-$bit key for S$-$AES

key $=[0$x$03,0$x$05,0$x$06,0$x$09]$

def shift$\_$rows$($state$)$:

# Swap second and third rows

state$[1],$ state$[2]=$ state$[2],$ state$[1]$

# Swap third and fourth rows

state$[2],$ state$[3]=$ state$[3],$ state$[2]$

return state

def mix$\_$columns$($state$)$:

# Multiply each column by $2$

for i in range$(4)$:

state$[$i$]=(($state$[$i$]<<1)^($state$[$i$]$ & $0$x$80$ and $0$x$1$B$))$ & $0$xFF

# XOR each column with the previous column

state$[1]^=$ state$[0]$

state$[2]^=$ state$[1]$

state$[3]^=$ state$[2]$

return state

def s$\_$aes$\_$encrypt$($plaintext$)$:

# Convert plaintext characters to ASCII values

plaintext$\_$ascii $=[$ord$($char$)$ for char in plaintext$]$

# Pad the plaintext if its length is not a multiple of $4$

while len$($plaintext$\_$ascii$)\%4!=0$:

plaintext$\_$ascii.append$(0)$

encrypted$\_$blocks $=[]$

for i in range$(0,$ len$($plaintext$\_$ascii$),4)$:

block $=$ plaintext$\_$ascii$[$i:i$+4]$

if len$($block$)<4$:

block.extend$([0]*(4-$ len$($block$)))$

# Initial round key addition

state $=[$byte $^$ key$[$idx$]$ for idx, byte in enumerate$($block$)]$

# S$-$AES rounds

for $\_$ in range$(3)$:

# Substitute each byte with its corresponding value in the s$\_$box

state $=[$s$\_$box$[$byte $>>4][$byte & $0$x$0$F$]$ for byte in state$]$

state $=$ shift$\_$rows$($state$)$

state $=$ mix$\_$columns$($state$)$

# Add the round key

state $=[$byte $^$ key$[$idx $+4]$ for idx, byte in enumerate$($state$)]$

# Final round without MixColumns

state $=[$s$\_$box$[$byte $>>4][$byte & $0$x$0$F$]$ for byte in state$]$

state $=$ shift$\_$rows$($state$)$

# Add the final round key

state $=[$byte $^$ key$[$idx $+16]$ for idx, byte in enumerate$($state$)]$

encrypted$\_$blocks.extend$($state$)$

return encrypted$\_$blocks

def s$\_$aes$\_$decrypt$($ciphertext$)$:

# Decryption in S$-$AES is similar to encryption for this simplified version

return s$\_$aes$\_$encrypt$($ciphertext$)$

# Input plaintext as a string

plaintext $=$ input$("$Enter plaintext: $")$

# Encrypt plaintext

encrypted $=$ s$\_$aes$\_$encrypt$($plaintext$)$

print$("$Encrypted:$",\text{'}\text{'}.$join$($f$\text{'}\{$byte:$02$X$\}\text{'}$ for byte in encrypted$))$

# Decrypt ciphertext

decrypted $=$ s$\_$aes$\_$decrypt$($encrypted$)$

# Remove padded zeros and convert ASCII values to characters for the decrypted result

decrypted$\_$text $=\text{'}\text{'}.$join$($chr$($byte$)$ for byte in decrypted if byte $!=0)$

print$("$Decrypted:$",$ decrypted$\_$text$)$