MASTER OF COMPUTER APPLICATIONS
Course Code : MCSL-017
Course Title : C and Assembly Language Programming
Assignment Number : MCA(1)/L017/Assign/2013
Write a Program in assembly language that has two subroutines: One for encrypting alphabets of a string and second for decrypting the encoded string. In Encryption, simply convert a character /number into its predefined numerical/character value. Decryption is a reverse process of encryption. Write suitable Main program in C that calls these function. Test your program suitably
DATA SEGMENT
MSG1 DB 10,13,’ENTER STRING HERE :- $’
MSG2 DB 10,13,’ENCRYPTED STRING IS :- $’
MSG3 DB 10,13,’DECRYPTED STRING IS : $’
P1 LABEL BYTE
M1 DB 0FFH
L1 DB ?
P11 DB 0FFH DUP (‘$’)
DATA ENDS
DISPLAY MACRO MSG
MOV AH,9
LEA DX,MSG
INT 21H
ENDM
CODE SEGMENT
ASSUME CS:CODE,DS:DATA
START:
MOV AX,DATA
MOV DS,AX
DISPLAY MSG1
LEA DX,P1
MOV AH,0AH
INT 21H
LEA SI,P11
MOV CL,L1
CALL ENCRYPT
DISPLAY MSG2
DISPLAY P11
LEA SI,P11
MOV CL,L1
CALL ENCRYPT
DISPLAY MSG3
DISPLAY P11
MOV AH,4CH
INT 21H
CODE ENDS
ENCRYPT PROC NEAR
MOV CH,0
CHECK1:
CMP [SI],2FH
JB DONE1
CMP [SI],3AH
JB NUM1
CMP [SI],41H
JB DONE1
CMP [SI],5BH
JB UPR1
CMP [SI],61H
JB DONE1
CMP [SI],7BH
JB LWR1
NUM1: CMP [SI],35H
JB LNUM1
SUB [SI],05H
JMP DONE1
LNUM1:
ADD [SI],05H
JMP DONE1
UPR1: CMP [SI],4EH
JB LUPR1
SUB [SI],0DH
JMP DONE1
LUPR1:
ADD [SI],0DH
JMP DONE1
LWR1: CMP [SI],6EH
JB LLWR1
SUB [SI],0DH
JMP DONE1
LLWR1:
ADD [SI],0DH
DONE1:
INC SI
LOOP CHECK1
RET
ENCRYPT ENDP
DECRYPT PROC NEAR
MOV CH,0
CHECK2:
CMP [SI],2FH
JB DONE2
CMP [SI],3AH
JB NUM2
CMP [SI],41H
JB DONE2
CMP [SI],5BH
JB UPR2
CMP [SI],61H
JB DONE2
CMP [SI],7BH
JB LWR2
NUM2: CMP [SI],35H
JB LNUM2
ADD [SI],05H
JMP DONE2
LNUM2:
SUB [SI],05H
JMP DONE2
UPR2: CMP [SI],4EH
JB LUPR2
ADD [SI],0DH
JMP DONE2
LUPR2:
SUB [SI],0DH
JMP DONE2
LWR2: CMP [SI],6EH
JB LLWR2
ADD [SI],0DH
JMP DONE2
LLWR2:
SUB [SI],0DH
DONE2:
INC SI
LOOP CHECK2
RET
DECRYPT ENDP
END START
program code :
[codesyntax lang=”asm” lines=”normal”]
DATA SEGMENT
MSG1 DB 10,13,’ENTER STRING HERE :- $’
MSG2 DB 10,13,’ENCRYPTED STRING IS :- $’
MSG3 DB 10,13,’DECRYPTED STRING IS : $’
P1 LABEL BYTE
M1 DB 0FFH
L1 DB ?
P11 DB 0FFH DUP (‘$’)
DATA ENDS
DISPLAY MACRO MSG
MOV AH,9
LEA DX,MSG
INT 21H
ENDM
CODE SEGMENT
ASSUME CS:CODE,DS:DATA
START:
MOV AX,DATA
MOV DS,AX
DISPLAY MSG1
LEA DX,P1
MOV AH,0AH
INT 21H
LEA SI,P11
MOV CL,L1
CALL ENCRYPT
DISPLAY MSG2
DISPLAY P11
LEA SI,P11
MOV CL,L1
CALL ENCRYPT
DISPLAY MSG3
DISPLAY P11
MOV AH,4CH
INT 21H
CODE ENDS
ENCRYPT PROC NEAR
MOV CH,0
CHECK1:
CMP [SI],2FH
JB DONE1
CMP [SI],3AH
JB NUM1
CMP [SI],41H
JB DONE1
CMP [SI],5BH
JB UPR1
CMP [SI],61H
JB DONE1
CMP [SI],7BH
JB LWR1
NUM1: CMP [SI],35H
JB LNUM1
SUB [SI],05H
JMP DONE1
LNUM1:
ADD [SI],05H
JMP DONE1
UPR1: CMP [SI],4EH
JB LUPR1
SUB [SI],0DH
JMP DONE1
LUPR1:
ADD [SI],0DH
JMP DONE1
LWR1: CMP [SI],6EH
JB LLWR1
SUB [SI],0DH
JMP DONE1
LLWR1:
ADD [SI],0DH
DONE1:
INC SI
LOOP CHECK1
RET
ENCRYPT ENDP
DECRYPT PROC NEAR
MOV CH,0
CHECK2:
CMP [SI],2FH
JB DONE2
CMP [SI],3AH
JB NUM2
CMP [SI],41H
JB DONE2
CMP [SI],5BH
JB UPR2
CMP [SI],61H
JB DONE2
CMP [SI],7BH
JB LWR2
NUM2: CMP [SI],35H
JB LNUM2
ADD [SI],05H
JMP DONE2
LNUM2:
SUB [SI],05H
JMP DONE2
UPR2: CMP [SI],4EH
JB LUPR2
ADD [SI],0DH
JMP DONE2
LUPR2:
SUB [SI],0DH
JMP DONE2
LWR2: CMP [SI],6EH
JB LLWR2
ADD [SI],0DH
JMP DONE2
LLWR2:
SUB [SI],0DH
DONE2:
INC SI
LOOP CHECK2
RET
DECRYPT ENDP
END START
[/codesyntax]
Screen shots :-
Output :-
