Assembly language Problem(And could you please attach a screenshot of your outpu

Question

Assembly language Problem(And could you please attach a screenshot of your output)

Part A 4. Encryption Using Rotate Operations Write a program that performs simple encryption by rotating each plaintext byte a varying num- ber of positions in different directions. For example, in the following array that represents the encryption key, a negative value indicates a rotation to the left and a positive value indicates a rotation to the right. The integer in each position indicates the magnitude of the rotation: key BYTE -2, 4, 1, 0, -3, 5, 2, -4, -4, 6 Your program should loop through a plaintext message and align the key to the first 10 bytes of the message. Rotate each plaintext byte by the amount indicated by its matching key amay value. Then, align the key to the next 10 bytes of the message and repeat the process. (A VideoNote for this exercise is posted on the Web site.) Part B 6. Greatest Common Divisor (GCD) The greatest common divisor (GCD) of two integers is the largest integer that will evenly divide both integers. The GCD algorithm involves integer division in a loop, described by the following C++ code: int GCD (int x, int y) x abs (x) absolute value y abs (y) do int n x 8 y y E n; while (y 0); return x; Implement this function in assembly language and write a test program that calls the function several times, passing it different values. Display all results on the screen.

Explanation / Answer

1) Assembly language code for Encryption using rotate operations.

INCLUDE Irvine32.inc
INCLUDE Macros.inc
BufSize = 80

.data

   key BYTE 6, 4, 1, 2, 7, 5, 2, 4, 3, 6
   myText BYTE "This text is going to be encrypted.", 0

   buffer BYTE BufSize DUP(?),0,0
   stdInHandle HANDLE ?
   bytesRead DWORD ?

.code
main PROC
   ;Pass the pointer to the text string in EDX,
   MOV EDX, OFFSET myText
  
   ;the array size to ECX
   MOV ECX, SIZEOF myText
  
   ;pointer to the key array in ESI,  
   MOV ESI, OFFSET key

   ;the direction value (0 or 1) in EBX
   MOV EBX, 0 ; rotate left for encryption

   call WriteString
   call Crlf

   call encDecText

   call WriteString
   call Crlf

   MOV EBX, 1
   call encDecText

   call WriteString
   call Crlf

   ;bonus - get string from console and encrypt
   mWriteln "Write a text to be encrypted."
   ; Get handle to standard input
   INVOKE GetStdHandle, STD_INPUT_HANDLE
   mov stdInHandle,eax
   ; Wait for user input
   INVOKE ReadConsole, stdInHandle, ADDR buffer,
   BufSize, ADDR bytesRead, 0

   ;encrypt and output to console
   MOV EDX, OFFSET buffer
   MOV ECX, BufSize
   MOV EBX, 0
   call encDecText
   call WriteString
   call Crlf

   ;decrypt and output to console
   MOV EBX, 1
   call encDecText
   call WriteString

   INVOKE ExitProcess,0 ; end the program
main ENDP

encDecText PROC
   ;Receives EDX - OFFSET of the text
   ; ECX - SIZE of the text
   ; ESI - OFFSET of the key
   ; EBX - rotation direction 0 for left 1 for right

   PUSHAD

   CMP EBX, 0
   JE equals
       MOV EBX, ESI
       ADD EBX, 9 ;the length of key
       loopNotEquals:

       MOV AL, [EDX] ; value of the text
       PUSH ECX
       MOV CL, [ESI] ; value of the key
       ROR AL, CL ; ror the text by the key
       MOV [EDX], AL
       POP ECX

       CMP ESI, EBX ; if all the keys are used, reset the offset so it uses the beginning
       JE reset1
      
       INC ESI
      
       JMP endReset1
       reset1:
       SUB ESI, 9
       endReset1:
      
       INC EDX
       loop loopNotEquals

       mWriteln "Input decrypted."
   JMP endCMP
   equals:
       MOV EBX, ESI
       ADD EBX, 9 ; the length of key
       loopEquals:

       MOV AL, [EDX] ; value of the text
       PUSH ECX
       MOV CL, [ESI] ; value of the key
       ROL AL, CL ; rol the text by the key
       MOV [EDX], AL
       POP ECX

       CMP ESI, EBX ; if all the keys are used, reset the offset so it uses the beginning
       JE reset2
       INC ESI
      
       JMP endReset2
       reset2:
       SUB ESI, 9
       endReset2:

       INC EDX
       loop loopEquals
       mWriteln "Input encrypted."
   endCMP:

   POPAD
   RET
encDecText ENDP
END main

2) Assembly language code for Greatest Common Divisor(GCD)

Include Irvine32.inc
.data
array SDWORD -1,-2,17,25,10,6,538,227,12,-36
str1 byte "Greatest common divisor is: ",0
.code
main PROC
mov ecx, LENGTHOF array /2
mov esi,OFFSET array
l1:
mov edi,2
l3:
mov eax,[esi]
add esi,4
cmp eax,0
jl l9
jmp l2
l9:
neg eax
l2:
push eax
dec edi
cmp edi,0
jne l3
call gcd
mov edx, offset str1
call writestring
call writedec
call crlf
loop l1
exit
main ENDP

gcd proc
pop edi
pop eax
pop ebx
gcd1:
mov edx,0
div ebx
mov eax,ebx
mov ebx,edx
cmp ebx,0
jg gcd1
push edi
ret
gcd endp

END main

Save the files with .asm extension.

Hope this helps. Thank you.

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