Encryption/Decryption Help

[samimmu]

hi guys



this is me Sam,actually i a new novice learner in c++ and i haven't gone that further, so far i just studied the basic things,such as definitions,loo ps,and slightly about variables,i have faced a problem when i tried to solve the question which is stated below, i use the ASCCI but i couldn't get properly, i found a lot of bugs in the program, i wish one of guys can respond me as soon as possible.






Your country is at war and your enemies are using a secret code to
communicate with each other. You have managed to intercept a message
that reads as follows:
:mmZ\dxZmx]Zpgy
The message is obviously encrypted using the enemy’s secret code. You
have just learned that their encryption method is based upon the ASCII code.
Individual characters in a string are encoded using this system. For example,
TCP1231 Computer Programming 1 Assignment 1
Page 3 of 6
the letter “A” is encoded using the number 65 and “B”is encoded using the
number 66.
Your enemy’s secret code takes each letter of the message and encrypts it as
follows:
If (OriginalChar + Key > 126) then
EncryptedChar = 32 + ((OriginalChar + Key) - 127)
Else
EncryptedChar = (OriginalChar + Key)
For example, if the enemy uses Key = 10 then the message “Hey” would be
encrypted as:
Character ASCII code
H
e
y
72
101
102
Encrypted H = (72 + 10) = 82 = R in ASCII
Encrypted e = (101 + 10) = 111 = o in ASCII
Encrypted y = ((121 + 10) - 127) = 36 = $ in ASCII
Consequently, “Hey” would be transmitted as “Ro$”.
Write a program that decrypts the intercepted message. You only know that
the key used is a number between 1 and 100. Your program should try to
decode the message using all possible keys between 1 and 100. When you
try the valid key, the message will make sense.





Regards:


sami alkindi



thank you

[stroken]

Post your code and be more specific about your problem.

[samimmu]

that was the code and the problem i couldn't answer it because i have not learn anything, i just learned about the basic things like output and inputs and variables nothing else..

[lqdeffx]

so if that is the case, I would suggest researching about loops and converting character's to their ascii values. that should give you all the necessary information, on top of what you already know, to complete that assignment. create something and let us know how it goes!

[RedSon]

The experts on this site are more than happy to help you with your problems but they cannot do your assignment/program for you. Attempt the assignment/program yourself first and post questions regarding any difficulties you have or about a particular function of the code that you don't know how to achieve.

Please read the Posting Guidelines and particularly the Coursework Posting Guidlines.

Then when you are ready post a new question in this thread.

MODERATOR

[samimmu]

so if that is the case, I would suggest researching about loops and converting character's to their ascii values. that should give you all the necessary information, on top of what you already know, to complete that assignment. create something and let us know how it goes!

thank you anyway,but actually i couldn't answer because i can not get the essential meaning of that question and i have no idea how i start even though i i have not done something that enable me to do it even to start it.

[sicarie]

thank you anyway,but actually i couldn't answer because i can not get the essential meaning of that question and i have no idea how i start even though i i have not done something that enable me to do it even to start it.

So you need to develop a program that will print out 100 messages, each one modifying a value back onto an ASCII value to get a second value?

[samimmu]

not really that exactly. i think the question was clear. it is how we decrypt somebody message if he or she using it as his or her privacy.how i can change the word from have a number (78+65) just example how can i decrypt that one.i wish you could help me out ...thank you

[sicarie]

Your program should try to
decode the message using all possible keys between 1 and 100. When you
try the valid key, the message will make sense.

Please correct me if I'm wrong, but that looks like 100 messages to me, and then the user will have to decipher it personally.

As I see it, the trick to this program is reading in a character, figuring out its ASCII value, and then either adding a number to it, or doing the simple calculation required. If you read in all the chars and figure out their values, then put that into an array, you can use a single for loop to get through the modification and printing.

[timmy]

friends...
i want a c++ code for image encryption and decryption ..i will grateful if u can send me on <email removed as per Posting Guidelines

[DeMan]

Hello Namesake

i want a c++ code for image encryption and decryption ..i will grateful if u can send me on

Ceaser Cipher?
RSA?
ECC?
AES?
maybe some Quantum Encryption?

[DeMan]

Your country is at war and your enemies are using a secret code to
communicate with each other. You have managed to intercept a message
that reads as follows:
:mmZ\dxZmx]Zpgy
The message is obviously encrypted using the enemy’s secret code. You
have just learned that their encryption method is based upon the ASCII code.
Individual characters in a string are encoded using this system. For example,
TCP1231 Computer Programming 1 Assignment 1
Page 3 of 6
the letter “A” is encoded using the number 65 and “B”is encoded using the
number 66.
Your enemy’s secret code takes each letter of the message and encrypts it as
follows:
If (OriginalChar + Key > 126) then
EncryptedChar = 32 + ((OriginalChar + Key) - 127)
Else
EncryptedChar = (OriginalChar + Key)
For example, if the enemy uses Key = 10 then the message “Hey” would be
encrypted as:
Character ASCII code
H
e
y
72
101
102
Encrypted H = (72 + 10) = 82 = R in ASCII
Encrypted e = (101 + 10) = 111 = o in ASCII
Encrypted y = ((121 + 10) - 127) = 36 = $ in ASCII
Consequently, “Hey” would be transmitted as “Ro$”.
Write a program that decrypts the intercepted message. You only know that
the key used is a number between 1 and 100. Your program should try to
decode the message using all possible keys between 1 and 100. When you
try the valid key, the message will make sense.

Seen very similar post recently....

(My country is at war....that narrows it down a little)

The letter "A" is encoded using the number 65.....sounds like ASCII,
The Number "B" is encoded using the number 66...Wait a minute there's a pattern



okie....now I've had my game./....
we have some pretty specific rules....

if(inChar + secretKey >126)
{
  newChar = 32 + ((inChar + secretKey) -127);
}
else
{
  newChar = (inChar + secretKey);
}

So we know how this message would be encrypted....

how would you decrypt this knowing the secret key?
maybe you could try first decrypting a known key.....

After that, you know the range of keys......
so you could try each one until one kives a good rresult....
}

[samimmu]

i am really grateful for you. i will try it, and thanks alot...


(My country is at war....that narrows it down a little)

The letter "A" is encoded using the number 65.....sounds like ASCII,
The Number "B" is encoded using the number 66...Wait a minute there's a pattern



okie....now I've had my game./....
we have some pretty specific rules....

if(inChar + secretKey >126)
{
  newChar = 32 + ((inChar + secretKey) -127);
}
else
{
  newChar = (inChar + secretKey);
}

So we know how this message would be encrypted....

how would you decrypt this knowing the secret key?
maybe you could try first decrypting a known key.....

After that, you know the range of keys......
so you could try each one until one kives a good rresult....
}[/QUOTE]

[DeMan]

Re the PM:

what doesn't work in this code?
This doesn't do everyhting you may want, it actually mimics the encryption process (That is, this code should help you to turn hey into Ro$)....

But once you can encrypt, you should be able to decrypt using an opposite method....

The key to solving the problem, is to understand the process involved, so once you understand how the encryption works, it should help you to understand the decryption.....

If you are still unsure on how to proceed, please post again, but please try to wxplain what it is that you don't understand....