CODEWITHSUNDEEP
algorithmencryptionencodingcryptography
Igor
Igor

Reputation: 2959

How to encrypt different messages in one encrypted text?

Here's an example for better understanding of the question:

2.0.0-p353 :003 > puts Base64.decode64 content
Glad to see we managed to get your attention! 
You'll find our message in the bottle. Choose one or more tools to open it; 
drop me a mail if you're interested in working together.

              $!'<
              ]!N3
          !9<Z]NWl!Z]N
            Q!]90!NW
             <6<K$E
             !'$*B0
             K-!N3!
             QW0o<!
             f$Z!fW
           <]]0K!<K!Q
       l]9NK!`Z<K6!-?$K6N
     !Z]NQ!f0!Z]<EE!`Z0!]90
    H!$!EN]!Z]NQ!$--!]90!fNW
    -!Z<EElf$EBZ!]N!]90!Z`'?
    0*]!E<K0!N3!lN`W!W0ZQNKZ
    0!3`EEZ]NQg1"LO^"OLFm"a[
    1"@%d%[+X=R^"(a^"+OIR=F1
    "IOX1"F%L7a%71["^O"=^"F=
    C1":%j1"1FI"+O4411[+X=R^
    "^mR1[+X=R^"[^OR"%.."^:1
    "R:X%[1"RmX%I=.O4.OOI"^O
    "^:1"[a(@1+^"F=L1"O4"mOa
    X"X1[ROL[1"4aFF[^ORh2#&Y
    2#JPe>M8#_P#&#\2Ye>,2#PY
    >2M_2/#&Y,;>_2,_bY2#PM#&
    #AeJ#)&\2/#\_&,D#b\>M8#\
    PJ2#G>)Y&Y>2\#PS2M\PbY,2
    /#)n#M2_5G>k#\_PS#&//#_;
    2#hPY/#J>G&MP#_P#_;2#\b)
    A2,_#G>M2#h;2M#\2M/>M8#b
       \#&#J&>G#5bGG\_PS


CLUE #1
def decode_char(ch):
    x = ord(ch) - 33
    return None if (x % 3) else ' ' if x < 3 else chr(x / 3 + 64)

CLUE #2
function decodeChar(ch) {
    var x = ch.charCodeAt(0) - 33
    if (String.fromCharCode(x % 3 + 64) != 'A')
        return null;
    else if (x < 3)
        return ' ';
    else
        return String.fromCharCode(x / 3 + 64)
}

CLUE #3
def decodeChar(c: Char): Option[Char] = c.toInt - 33 match {
    case 2              => Some(' ')
    case x if x % 3 > 1 => Some((x/3 + 64).toChar)
    case _              => None
}
 => nil

The functions listed below the bottle do decode the bottle in a different ways. For example, JS code gives this:

"WE NOT ONLY USE JAVASCRIPT BUT COMPILE MORE LANGUAGES TO IT LIKE HAXE ELM COFFEESCRIPT TYPESCRIPT STOP ADD THE PHRASE PYRAMIDOFDOOM TO THE SUBJECT LINE OF YOUR RESPONSE FULL"

Other functions are giving different texts.

So the question here is: How to encrypt different texts in one "bottle" (encrypted text)?

Upvotes: 0

Views: 135

Answers (1)

JimmyB
JimmyB

Reputation: 12620

Each character has a value encoded in it that denotes which algorithm is needed for decoding.

return None if (x % 3) -> Anything not a multiple of 3 (n%3 != 0) is ignored.

if (String.fromCharCode(x % 3 + 64) != 'A') return null; -> All characters not (n*3)+1, i.e. n%3 != 1, are ignored

if x % 3 > 1 => ... -> only characters with (n%3) > 1, i.e. n%3 = 2, are decoded, others are ignored.

EDIT:

The encryption can be inferred as

c_output = ((c_input-64) * 3) + msg_no

where msg_no is the number of the message (less than 3) the input character belongs to.

If you take a bigger number than 3 you can encode more different messages into the same stream. However, it is important that c_output is still in the valid range for the datatype, e.g. a single ASCII character or byte. With 3 different message streams, encoding a µ (code 181 in ASCII) is not possible: (181-64) * 3 > 255. Equally, 9 (code 57 in ASCII) cannot be encoded because (57-64)*3 < 0.

Upvotes: 1

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